| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Generic ring buffer |
| * |
| * Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com> |
| */ |
| #include <linux/trace_events.h> |
| #include <linux/ring_buffer.h> |
| #include <linux/trace_clock.h> |
| #include <linux/sched/clock.h> |
| #include <linux/trace_seq.h> |
| #include <linux/spinlock.h> |
| #include <linux/irq_work.h> |
| #include <linux/uaccess.h> |
| #include <linux/hardirq.h> |
| #include <linux/kthread.h> /* for self test */ |
| #include <linux/module.h> |
| #include <linux/percpu.h> |
| #include <linux/mutex.h> |
| #include <linux/delay.h> |
| #include <linux/slab.h> |
| #include <linux/init.h> |
| #include <linux/hash.h> |
| #include <linux/list.h> |
| #include <linux/cpu.h> |
| #include <linux/oom.h> |
| |
| #include <asm/local.h> |
| |
| static void update_pages_handler(struct work_struct *work); |
| |
| /* |
| * The ring buffer header is special. We must manually up keep it. |
| */ |
| int ring_buffer_print_entry_header(struct trace_seq *s) |
| { |
| trace_seq_puts(s, "# compressed entry header\n"); |
| trace_seq_puts(s, "\ttype_len : 5 bits\n"); |
| trace_seq_puts(s, "\ttime_delta : 27 bits\n"); |
| trace_seq_puts(s, "\tarray : 32 bits\n"); |
| trace_seq_putc(s, '\n'); |
| trace_seq_printf(s, "\tpadding : type == %d\n", |
| RINGBUF_TYPE_PADDING); |
| trace_seq_printf(s, "\ttime_extend : type == %d\n", |
| RINGBUF_TYPE_TIME_EXTEND); |
| trace_seq_printf(s, "\ttime_stamp : type == %d\n", |
| RINGBUF_TYPE_TIME_STAMP); |
| trace_seq_printf(s, "\tdata max type_len == %d\n", |
| RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
| |
| return !trace_seq_has_overflowed(s); |
| } |
| |
| /* |
| * The ring buffer is made up of a list of pages. A separate list of pages is |
| * allocated for each CPU. A writer may only write to a buffer that is |
| * associated with the CPU it is currently executing on. A reader may read |
| * from any per cpu buffer. |
| * |
| * The reader is special. For each per cpu buffer, the reader has its own |
| * reader page. When a reader has read the entire reader page, this reader |
| * page is swapped with another page in the ring buffer. |
| * |
| * Now, as long as the writer is off the reader page, the reader can do what |
| * ever it wants with that page. The writer will never write to that page |
| * again (as long as it is out of the ring buffer). |
| * |
| * Here's some silly ASCII art. |
| * |
| * +------+ |
| * |reader| RING BUFFER |
| * |page | |
| * +------+ +---+ +---+ +---+ |
| * | |-->| |-->| | |
| * +---+ +---+ +---+ |
| * ^ | |
| * | | |
| * +---------------+ |
| * |
| * |
| * +------+ |
| * |reader| RING BUFFER |
| * |page |------------------v |
| * +------+ +---+ +---+ +---+ |
| * | |-->| |-->| | |
| * +---+ +---+ +---+ |
| * ^ | |
| * | | |
| * +---------------+ |
| * |
| * |
| * +------+ |
| * |reader| RING BUFFER |
| * |page |------------------v |
| * +------+ +---+ +---+ +---+ |
| * ^ | |-->| |-->| | |
| * | +---+ +---+ +---+ |
| * | | |
| * | | |
| * +------------------------------+ |
| * |
| * |
| * +------+ |
| * |buffer| RING BUFFER |
| * |page |------------------v |
| * +------+ +---+ +---+ +---+ |
| * ^ | | | |-->| | |
| * | New +---+ +---+ +---+ |
| * | Reader------^ | |
| * | page | |
| * +------------------------------+ |
| * |
| * |
| * After we make this swap, the reader can hand this page off to the splice |
| * code and be done with it. It can even allocate a new page if it needs to |
| * and swap that into the ring buffer. |
| * |
| * We will be using cmpxchg soon to make all this lockless. |
| * |
| */ |
| |
| /* Used for individual buffers (after the counter) */ |
| #define RB_BUFFER_OFF (1 << 20) |
| |
| #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) |
| |
| #define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array)) |
| #define RB_ALIGNMENT 4U |
| #define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
| #define RB_EVNT_MIN_SIZE 8U /* two 32bit words */ |
| #define RB_ALIGN_DATA __aligned(RB_ALIGNMENT) |
| |
| /* define RINGBUF_TYPE_DATA for 'case RINGBUF_TYPE_DATA:' */ |
| #define RINGBUF_TYPE_DATA 0 ... RINGBUF_TYPE_DATA_TYPE_LEN_MAX |
| |
| enum { |
| RB_LEN_TIME_EXTEND = 8, |
| RB_LEN_TIME_STAMP = 8, |
| }; |
| |
| #define skip_time_extend(event) \ |
| ((struct ring_buffer_event *)((char *)event + RB_LEN_TIME_EXTEND)) |
| |
| #define extended_time(event) \ |
| (event->type_len >= RINGBUF_TYPE_TIME_EXTEND) |
| |
| static inline int rb_null_event(struct ring_buffer_event *event) |
| { |
| return event->type_len == RINGBUF_TYPE_PADDING && !event->time_delta; |
| } |
| |
| static void rb_event_set_padding(struct ring_buffer_event *event) |
| { |
| /* padding has a NULL time_delta */ |
| event->type_len = RINGBUF_TYPE_PADDING; |
| event->time_delta = 0; |
| } |
| |
| static unsigned |
| rb_event_data_length(struct ring_buffer_event *event) |
| { |
| unsigned length; |
| |
| if (event->type_len) |
| length = event->type_len * RB_ALIGNMENT; |
| else |
| length = event->array[0]; |
| return length + RB_EVNT_HDR_SIZE; |
| } |
| |
| /* |
| * Return the length of the given event. Will return |
| * the length of the time extend if the event is a |
| * time extend. |
| */ |
| static inline unsigned |
| rb_event_length(struct ring_buffer_event *event) |
| { |
| switch (event->type_len) { |
| case RINGBUF_TYPE_PADDING: |
| if (rb_null_event(event)) |
| /* undefined */ |
| return -1; |
| return event->array[0] + RB_EVNT_HDR_SIZE; |
| |
| case RINGBUF_TYPE_TIME_EXTEND: |
| return RB_LEN_TIME_EXTEND; |
| |
| case RINGBUF_TYPE_TIME_STAMP: |
| return RB_LEN_TIME_STAMP; |
| |
| case RINGBUF_TYPE_DATA: |
| return rb_event_data_length(event); |
| default: |
| BUG(); |
| } |
| /* not hit */ |
| return 0; |
| } |
| |
| /* |
| * Return total length of time extend and data, |
| * or just the event length for all other events. |
| */ |
| static inline unsigned |
| rb_event_ts_length(struct ring_buffer_event *event) |
| { |
| unsigned len = 0; |
| |
| if (extended_time(event)) { |
| /* time extends include the data event after it */ |
| len = RB_LEN_TIME_EXTEND; |
| event = skip_time_extend(event); |
| } |
| return len + rb_event_length(event); |
| } |
| |
| /** |
| * ring_buffer_event_length - return the length of the event |
| * @event: the event to get the length of |
| * |
| * Returns the size of the data load of a data event. |
| * If the event is something other than a data event, it |
| * returns the size of the event itself. With the exception |
| * of a TIME EXTEND, where it still returns the size of the |
| * data load of the data event after it. |
| */ |
| unsigned ring_buffer_event_length(struct ring_buffer_event *event) |
| { |
| unsigned length; |
| |
| if (extended_time(event)) |
| event = skip_time_extend(event); |
| |
| length = rb_event_length(event); |
| if (event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX) |
| return length; |
| length -= RB_EVNT_HDR_SIZE; |
| if (length > RB_MAX_SMALL_DATA + sizeof(event->array[0])) |
| length -= sizeof(event->array[0]); |
| return length; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_event_length); |
| |
| /* inline for ring buffer fast paths */ |
| static __always_inline void * |
| rb_event_data(struct ring_buffer_event *event) |
| { |
| if (extended_time(event)) |
| event = skip_time_extend(event); |
| BUG_ON(event->type_len > RINGBUF_TYPE_DATA_TYPE_LEN_MAX); |
| /* If length is in len field, then array[0] has the data */ |
| if (event->type_len) |
| return (void *)&event->array[0]; |
| /* Otherwise length is in array[0] and array[1] has the data */ |
| return (void *)&event->array[1]; |
| } |
| |
| /** |
| * ring_buffer_event_data - return the data of the event |
| * @event: the event to get the data from |
| */ |
| void *ring_buffer_event_data(struct ring_buffer_event *event) |
| { |
| return rb_event_data(event); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_event_data); |
| |
| #define for_each_buffer_cpu(buffer, cpu) \ |
| for_each_cpu(cpu, buffer->cpumask) |
| |
| #define TS_SHIFT 27 |
| #define TS_MASK ((1ULL << TS_SHIFT) - 1) |
| #define TS_DELTA_TEST (~TS_MASK) |
| |
| /** |
| * ring_buffer_event_time_stamp - return the event's extended timestamp |
| * @event: the event to get the timestamp of |
| * |
| * Returns the extended timestamp associated with a data event. |
| * An extended time_stamp is a 64-bit timestamp represented |
| * internally in a special way that makes the best use of space |
| * contained within a ring buffer event. This function decodes |
| * it and maps it to a straight u64 value. |
| */ |
| u64 ring_buffer_event_time_stamp(struct ring_buffer_event *event) |
| { |
| u64 ts; |
| |
| ts = event->array[0]; |
| ts <<= TS_SHIFT; |
| ts += event->time_delta; |
| |
| return ts; |
| } |
| |
| /* Flag when events were overwritten */ |
| #define RB_MISSED_EVENTS (1 << 31) |
| /* Missed count stored at end */ |
| #define RB_MISSED_STORED (1 << 30) |
| |
| #define RB_MISSED_FLAGS (RB_MISSED_EVENTS|RB_MISSED_STORED) |
| |
| struct buffer_data_page { |
| u64 time_stamp; /* page time stamp */ |
| local_t commit; /* write committed index */ |
| unsigned char data[] RB_ALIGN_DATA; /* data of buffer page */ |
| }; |
| |
| /* |
| * Note, the buffer_page list must be first. The buffer pages |
| * are allocated in cache lines, which means that each buffer |
| * page will be at the beginning of a cache line, and thus |
| * the least significant bits will be zero. We use this to |
| * add flags in the list struct pointers, to make the ring buffer |
| * lockless. |
| */ |
| struct buffer_page { |
| struct list_head list; /* list of buffer pages */ |
| local_t write; /* index for next write */ |
| unsigned read; /* index for next read */ |
| local_t entries; /* entries on this page */ |
| unsigned long real_end; /* real end of data */ |
| struct buffer_data_page *page; /* Actual data page */ |
| }; |
| |
| /* |
| * The buffer page counters, write and entries, must be reset |
| * atomically when crossing page boundaries. To synchronize this |
| * update, two counters are inserted into the number. One is |
| * the actual counter for the write position or count on the page. |
| * |
| * The other is a counter of updaters. Before an update happens |
| * the update partition of the counter is incremented. This will |
| * allow the updater to update the counter atomically. |
| * |
| * The counter is 20 bits, and the state data is 12. |
| */ |
| #define RB_WRITE_MASK 0xfffff |
| #define RB_WRITE_INTCNT (1 << 20) |
| |
| static void rb_init_page(struct buffer_data_page *bpage) |
| { |
| local_set(&bpage->commit, 0); |
| } |
| |
| /* |
| * Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing |
| * this issue out. |
| */ |
| static void free_buffer_page(struct buffer_page *bpage) |
| { |
| free_page((unsigned long)bpage->page); |
| kfree(bpage); |
| } |
| |
| /* |
| * We need to fit the time_stamp delta into 27 bits. |
| */ |
| static inline int test_time_stamp(u64 delta) |
| { |
| if (delta & TS_DELTA_TEST) |
| return 1; |
| return 0; |
| } |
| |
| #define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE) |
| |
| /* Max payload is BUF_PAGE_SIZE - header (8bytes) */ |
| #define BUF_MAX_DATA_SIZE (BUF_PAGE_SIZE - (sizeof(u32) * 2)) |
| |
| int ring_buffer_print_page_header(struct trace_seq *s) |
| { |
| struct buffer_data_page field; |
| |
| trace_seq_printf(s, "\tfield: u64 timestamp;\t" |
| "offset:0;\tsize:%u;\tsigned:%u;\n", |
| (unsigned int)sizeof(field.time_stamp), |
| (unsigned int)is_signed_type(u64)); |
| |
| trace_seq_printf(s, "\tfield: local_t commit;\t" |
| "offset:%u;\tsize:%u;\tsigned:%u;\n", |
| (unsigned int)offsetof(typeof(field), commit), |
| (unsigned int)sizeof(field.commit), |
| (unsigned int)is_signed_type(long)); |
| |
| trace_seq_printf(s, "\tfield: int overwrite;\t" |
| "offset:%u;\tsize:%u;\tsigned:%u;\n", |
| (unsigned int)offsetof(typeof(field), commit), |
| 1, |
| (unsigned int)is_signed_type(long)); |
| |
| trace_seq_printf(s, "\tfield: char data;\t" |
| "offset:%u;\tsize:%u;\tsigned:%u;\n", |
| (unsigned int)offsetof(typeof(field), data), |
| (unsigned int)BUF_PAGE_SIZE, |
| (unsigned int)is_signed_type(char)); |
| |
| return !trace_seq_has_overflowed(s); |
| } |
| |
| struct rb_irq_work { |
| struct irq_work work; |
| wait_queue_head_t waiters; |
| wait_queue_head_t full_waiters; |
| bool waiters_pending; |
| bool full_waiters_pending; |
| bool wakeup_full; |
| }; |
| |
| /* |
| * Structure to hold event state and handle nested events. |
| */ |
| struct rb_event_info { |
| u64 ts; |
| u64 delta; |
| unsigned long length; |
| struct buffer_page *tail_page; |
| int add_timestamp; |
| }; |
| |
| /* |
| * Used for which event context the event is in. |
| * NMI = 0 |
| * IRQ = 1 |
| * SOFTIRQ = 2 |
| * NORMAL = 3 |
| * |
| * See trace_recursive_lock() comment below for more details. |
| */ |
| enum { |
| RB_CTX_NMI, |
| RB_CTX_IRQ, |
| RB_CTX_SOFTIRQ, |
| RB_CTX_NORMAL, |
| RB_CTX_MAX |
| }; |
| |
| /* |
| * head_page == tail_page && head == tail then buffer is empty. |
| */ |
| struct ring_buffer_per_cpu { |
| int cpu; |
| atomic_t record_disabled; |
| struct ring_buffer *buffer; |
| raw_spinlock_t reader_lock; /* serialize readers */ |
| arch_spinlock_t lock; |
| struct lock_class_key lock_key; |
| struct buffer_data_page *free_page; |
| unsigned long nr_pages; |
| unsigned int current_context; |
| struct list_head *pages; |
| struct buffer_page *head_page; /* read from head */ |
| struct buffer_page *tail_page; /* write to tail */ |
| struct buffer_page *commit_page; /* committed pages */ |
| struct buffer_page *reader_page; |
| unsigned long lost_events; |
| unsigned long last_overrun; |
| unsigned long nest; |
| local_t entries_bytes; |
| local_t entries; |
| local_t overrun; |
| local_t commit_overrun; |
| local_t dropped_events; |
| local_t committing; |
| local_t commits; |
| local_t pages_touched; |
| local_t pages_read; |
| long last_pages_touch; |
| size_t shortest_full; |
| unsigned long read; |
| unsigned long read_bytes; |
| u64 write_stamp; |
| u64 read_stamp; |
| /* ring buffer pages to update, > 0 to add, < 0 to remove */ |
| long nr_pages_to_update; |
| struct list_head new_pages; /* new pages to add */ |
| struct work_struct update_pages_work; |
| struct completion update_done; |
| |
| struct rb_irq_work irq_work; |
| }; |
| |
| struct ring_buffer { |
| unsigned flags; |
| int cpus; |
| atomic_t record_disabled; |
| atomic_t resize_disabled; |
| cpumask_var_t cpumask; |
| |
| struct lock_class_key *reader_lock_key; |
| |
| struct mutex mutex; |
| |
| struct ring_buffer_per_cpu **buffers; |
| |
| struct hlist_node node; |
| u64 (*clock)(void); |
| |
| struct rb_irq_work irq_work; |
| bool time_stamp_abs; |
| }; |
| |
| struct ring_buffer_iter { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| unsigned long head; |
| struct buffer_page *head_page; |
| struct buffer_page *cache_reader_page; |
| unsigned long cache_read; |
| u64 read_stamp; |
| }; |
| |
| /** |
| * ring_buffer_nr_pages - get the number of buffer pages in the ring buffer |
| * @buffer: The ring_buffer to get the number of pages from |
| * @cpu: The cpu of the ring_buffer to get the number of pages from |
| * |
| * Returns the number of pages used by a per_cpu buffer of the ring buffer. |
| */ |
| size_t ring_buffer_nr_pages(struct ring_buffer *buffer, int cpu) |
| { |
| return buffer->buffers[cpu]->nr_pages; |
| } |
| |
| /** |
| * ring_buffer_nr_pages_dirty - get the number of used pages in the ring buffer |
| * @buffer: The ring_buffer to get the number of pages from |
| * @cpu: The cpu of the ring_buffer to get the number of pages from |
| * |
| * Returns the number of pages that have content in the ring buffer. |
| */ |
| size_t ring_buffer_nr_dirty_pages(struct ring_buffer *buffer, int cpu) |
| { |
| size_t read; |
| size_t cnt; |
| |
| read = local_read(&buffer->buffers[cpu]->pages_read); |
| cnt = local_read(&buffer->buffers[cpu]->pages_touched); |
| /* The reader can read an empty page, but not more than that */ |
| if (cnt < read) { |
| WARN_ON_ONCE(read > cnt + 1); |
| return 0; |
| } |
| |
| return cnt - read; |
| } |
| |
| /* |
| * rb_wake_up_waiters - wake up tasks waiting for ring buffer input |
| * |
| * Schedules a delayed work to wake up any task that is blocked on the |
| * ring buffer waiters queue. |
| */ |
| static void rb_wake_up_waiters(struct irq_work *work) |
| { |
| struct rb_irq_work *rbwork = container_of(work, struct rb_irq_work, work); |
| |
| wake_up_all(&rbwork->waiters); |
| if (rbwork->wakeup_full) { |
| rbwork->wakeup_full = false; |
| wake_up_all(&rbwork->full_waiters); |
| } |
| } |
| |
| /** |
| * ring_buffer_wait - wait for input to the ring buffer |
| * @buffer: buffer to wait on |
| * @cpu: the cpu buffer to wait on |
| * @full: wait until a full page is available, if @cpu != RING_BUFFER_ALL_CPUS |
| * |
| * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
| * as data is added to any of the @buffer's cpu buffers. Otherwise |
| * it will wait for data to be added to a specific cpu buffer. |
| */ |
| int ring_buffer_wait(struct ring_buffer *buffer, int cpu, int full) |
| { |
| struct ring_buffer_per_cpu *uninitialized_var(cpu_buffer); |
| DEFINE_WAIT(wait); |
| struct rb_irq_work *work; |
| int ret = 0; |
| |
| /* |
| * Depending on what the caller is waiting for, either any |
| * data in any cpu buffer, or a specific buffer, put the |
| * caller on the appropriate wait queue. |
| */ |
| if (cpu == RING_BUFFER_ALL_CPUS) { |
| work = &buffer->irq_work; |
| /* Full only makes sense on per cpu reads */ |
| full = 0; |
| } else { |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return -ENODEV; |
| cpu_buffer = buffer->buffers[cpu]; |
| work = &cpu_buffer->irq_work; |
| } |
| |
| |
| while (true) { |
| if (full) |
| prepare_to_wait(&work->full_waiters, &wait, TASK_INTERRUPTIBLE); |
| else |
| prepare_to_wait(&work->waiters, &wait, TASK_INTERRUPTIBLE); |
| |
| /* |
| * The events can happen in critical sections where |
| * checking a work queue can cause deadlocks. |
| * After adding a task to the queue, this flag is set |
| * only to notify events to try to wake up the queue |
| * using irq_work. |
| * |
| * We don't clear it even if the buffer is no longer |
| * empty. The flag only causes the next event to run |
| * irq_work to do the work queue wake up. The worse |
| * that can happen if we race with !trace_empty() is that |
| * an event will cause an irq_work to try to wake up |
| * an empty queue. |
| * |
| * There's no reason to protect this flag either, as |
| * the work queue and irq_work logic will do the necessary |
| * synchronization for the wake ups. The only thing |
| * that is necessary is that the wake up happens after |
| * a task has been queued. It's OK for spurious wake ups. |
| */ |
| if (full) |
| work->full_waiters_pending = true; |
| else |
| work->waiters_pending = true; |
| |
| if (signal_pending(current)) { |
| ret = -EINTR; |
| break; |
| } |
| |
| if (cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) |
| break; |
| |
| if (cpu != RING_BUFFER_ALL_CPUS && |
| !ring_buffer_empty_cpu(buffer, cpu)) { |
| unsigned long flags; |
| bool pagebusy; |
| size_t nr_pages; |
| size_t dirty; |
| |
| if (!full) |
| break; |
| |
| raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
| pagebusy = cpu_buffer->reader_page == cpu_buffer->commit_page; |
| nr_pages = cpu_buffer->nr_pages; |
| dirty = ring_buffer_nr_dirty_pages(buffer, cpu); |
| if (!cpu_buffer->shortest_full || |
| cpu_buffer->shortest_full < full) |
| cpu_buffer->shortest_full = full; |
| raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
| if (!pagebusy && |
| (!nr_pages || (dirty * 100) > full * nr_pages)) |
| break; |
| } |
| |
| schedule(); |
| } |
| |
| if (full) |
| finish_wait(&work->full_waiters, &wait); |
| else |
| finish_wait(&work->waiters, &wait); |
| |
| return ret; |
| } |
| |
| /** |
| * ring_buffer_poll_wait - poll on buffer input |
| * @buffer: buffer to wait on |
| * @cpu: the cpu buffer to wait on |
| * @filp: the file descriptor |
| * @poll_table: The poll descriptor |
| * |
| * If @cpu == RING_BUFFER_ALL_CPUS then the task will wake up as soon |
| * as data is added to any of the @buffer's cpu buffers. Otherwise |
| * it will wait for data to be added to a specific cpu buffer. |
| * |
| * Returns EPOLLIN | EPOLLRDNORM if data exists in the buffers, |
| * zero otherwise. |
| */ |
| __poll_t ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu, |
| struct file *filp, poll_table *poll_table) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| struct rb_irq_work *work; |
| |
| if (cpu == RING_BUFFER_ALL_CPUS) |
| work = &buffer->irq_work; |
| else { |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return -EINVAL; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| work = &cpu_buffer->irq_work; |
| } |
| |
| poll_wait(filp, &work->waiters, poll_table); |
| work->waiters_pending = true; |
| /* |
| * There's a tight race between setting the waiters_pending and |
| * checking if the ring buffer is empty. Once the waiters_pending bit |
| * is set, the next event will wake the task up, but we can get stuck |
| * if there's only a single event in. |
| * |
| * FIXME: Ideally, we need a memory barrier on the writer side as well, |
| * but adding a memory barrier to all events will cause too much of a |
| * performance hit in the fast path. We only need a memory barrier when |
| * the buffer goes from empty to having content. But as this race is |
| * extremely small, and it's not a problem if another event comes in, we |
| * will fix it later. |
| */ |
| smp_mb(); |
| |
| if ((cpu == RING_BUFFER_ALL_CPUS && !ring_buffer_empty(buffer)) || |
| (cpu != RING_BUFFER_ALL_CPUS && !ring_buffer_empty_cpu(buffer, cpu))) |
| return EPOLLIN | EPOLLRDNORM; |
| return 0; |
| } |
| |
| /* buffer may be either ring_buffer or ring_buffer_per_cpu */ |
| #define RB_WARN_ON(b, cond) \ |
| ({ \ |
| int _____ret = unlikely(cond); \ |
| if (_____ret) { \ |
| if (__same_type(*(b), struct ring_buffer_per_cpu)) { \ |
| struct ring_buffer_per_cpu *__b = \ |
| (void *)b; \ |
| atomic_inc(&__b->buffer->record_disabled); \ |
| } else \ |
| atomic_inc(&b->record_disabled); \ |
| WARN_ON(1); \ |
| } \ |
| _____ret; \ |
| }) |
| |
| /* Up this if you want to test the TIME_EXTENTS and normalization */ |
| #define DEBUG_SHIFT 0 |
| |
| static inline u64 rb_time_stamp(struct ring_buffer *buffer) |
| { |
| /* shift to debug/test normalization and TIME_EXTENTS */ |
| return buffer->clock() << DEBUG_SHIFT; |
| } |
| |
| u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu) |
| { |
| u64 time; |
| |
| preempt_disable_notrace(); |
| time = rb_time_stamp(buffer); |
| preempt_enable_notrace(); |
| |
| return time; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_time_stamp); |
| |
| void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer, |
| int cpu, u64 *ts) |
| { |
| /* Just stupid testing the normalize function and deltas */ |
| *ts >>= DEBUG_SHIFT; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp); |
| |
| /* |
| * Making the ring buffer lockless makes things tricky. |
| * Although writes only happen on the CPU that they are on, |
| * and they only need to worry about interrupts. Reads can |
| * happen on any CPU. |
| * |
| * The reader page is always off the ring buffer, but when the |
| * reader finishes with a page, it needs to swap its page with |
| * a new one from the buffer. The reader needs to take from |
| * the head (writes go to the tail). But if a writer is in overwrite |
| * mode and wraps, it must push the head page forward. |
| * |
| * Here lies the problem. |
| * |
| * The reader must be careful to replace only the head page, and |
| * not another one. As described at the top of the file in the |
| * ASCII art, the reader sets its old page to point to the next |
| * page after head. It then sets the page after head to point to |
| * the old reader page. But if the writer moves the head page |
| * during this operation, the reader could end up with the tail. |
| * |
| * We use cmpxchg to help prevent this race. We also do something |
| * special with the page before head. We set the LSB to 1. |
| * |
| * When the writer must push the page forward, it will clear the |
| * bit that points to the head page, move the head, and then set |
| * the bit that points to the new head page. |
| * |
| * We also don't want an interrupt coming in and moving the head |
| * page on another writer. Thus we use the second LSB to catch |
| * that too. Thus: |
| * |
| * head->list->prev->next bit 1 bit 0 |
| * ------- ------- |
| * Normal page 0 0 |
| * Points to head page 0 1 |
| * New head page 1 0 |
| * |
| * Note we can not trust the prev pointer of the head page, because: |
| * |
| * +----+ +-----+ +-----+ |
| * | |------>| T |---X--->| N | |
| * | |<------| | | | |
| * +----+ +-----+ +-----+ |
| * ^ ^ | |
| * | +-----+ | | |
| * +----------| R |----------+ | |
| * | |<-----------+ |
| * +-----+ |
| * |
| * Key: ---X--> HEAD flag set in pointer |
| * T Tail page |
| * R Reader page |
| * N Next page |
| * |
| * (see __rb_reserve_next() to see where this happens) |
| * |
| * What the above shows is that the reader just swapped out |
| * the reader page with a page in the buffer, but before it |
| * could make the new header point back to the new page added |
| * it was preempted by a writer. The writer moved forward onto |
| * the new page added by the reader and is about to move forward |
| * again. |
| * |
| * You can see, it is legitimate for the previous pointer of |
| * the head (or any page) not to point back to itself. But only |
| * temporarily. |
| */ |
| |
| #define RB_PAGE_NORMAL 0UL |
| #define RB_PAGE_HEAD 1UL |
| #define RB_PAGE_UPDATE 2UL |
| |
| |
| #define RB_FLAG_MASK 3UL |
| |
| /* PAGE_MOVED is not part of the mask */ |
| #define RB_PAGE_MOVED 4UL |
| |
| /* |
| * rb_list_head - remove any bit |
| */ |
| static struct list_head *rb_list_head(struct list_head *list) |
| { |
| unsigned long val = (unsigned long)list; |
| |
| return (struct list_head *)(val & ~RB_FLAG_MASK); |
| } |
| |
| /* |
| * rb_is_head_page - test if the given page is the head page |
| * |
| * Because the reader may move the head_page pointer, we can |
| * not trust what the head page is (it may be pointing to |
| * the reader page). But if the next page is a header page, |
| * its flags will be non zero. |
| */ |
| static inline int |
| rb_is_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *page, struct list_head *list) |
| { |
| unsigned long val; |
| |
| val = (unsigned long)list->next; |
| |
| if ((val & ~RB_FLAG_MASK) != (unsigned long)&page->list) |
| return RB_PAGE_MOVED; |
| |
| return val & RB_FLAG_MASK; |
| } |
| |
| /* |
| * rb_is_reader_page |
| * |
| * The unique thing about the reader page, is that, if the |
| * writer is ever on it, the previous pointer never points |
| * back to the reader page. |
| */ |
| static bool rb_is_reader_page(struct buffer_page *page) |
| { |
| struct list_head *list = page->list.prev; |
| |
| return rb_list_head(list->next) != &page->list; |
| } |
| |
| /* |
| * rb_set_list_to_head - set a list_head to be pointing to head. |
| */ |
| static void rb_set_list_to_head(struct ring_buffer_per_cpu *cpu_buffer, |
| struct list_head *list) |
| { |
| unsigned long *ptr; |
| |
| ptr = (unsigned long *)&list->next; |
| *ptr |= RB_PAGE_HEAD; |
| *ptr &= ~RB_PAGE_UPDATE; |
| } |
| |
| /* |
| * rb_head_page_activate - sets up head page |
| */ |
| static void rb_head_page_activate(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct buffer_page *head; |
| |
| head = cpu_buffer->head_page; |
| if (!head) |
| return; |
| |
| /* |
| * Set the previous list pointer to have the HEAD flag. |
| */ |
| rb_set_list_to_head(cpu_buffer, head->list.prev); |
| } |
| |
| static void rb_list_head_clear(struct list_head *list) |
| { |
| unsigned long *ptr = (unsigned long *)&list->next; |
| |
| *ptr &= ~RB_FLAG_MASK; |
| } |
| |
| /* |
| * rb_head_page_deactivate - clears head page ptr (for free list) |
| */ |
| static void |
| rb_head_page_deactivate(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct list_head *hd; |
| |
| /* Go through the whole list and clear any pointers found. */ |
| rb_list_head_clear(cpu_buffer->pages); |
| |
| list_for_each(hd, cpu_buffer->pages) |
| rb_list_head_clear(hd); |
| } |
| |
| static int rb_head_page_set(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *head, |
| struct buffer_page *prev, |
| int old_flag, int new_flag) |
| { |
| struct list_head *list; |
| unsigned long val = (unsigned long)&head->list; |
| unsigned long ret; |
| |
| list = &prev->list; |
| |
| val &= ~RB_FLAG_MASK; |
| |
| ret = cmpxchg((unsigned long *)&list->next, |
| val | old_flag, val | new_flag); |
| |
| /* check if the reader took the page */ |
| if ((ret & ~RB_FLAG_MASK) != val) |
| return RB_PAGE_MOVED; |
| |
| return ret & RB_FLAG_MASK; |
| } |
| |
| static int rb_head_page_set_update(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *head, |
| struct buffer_page *prev, |
| int old_flag) |
| { |
| return rb_head_page_set(cpu_buffer, head, prev, |
| old_flag, RB_PAGE_UPDATE); |
| } |
| |
| static int rb_head_page_set_head(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *head, |
| struct buffer_page *prev, |
| int old_flag) |
| { |
| return rb_head_page_set(cpu_buffer, head, prev, |
| old_flag, RB_PAGE_HEAD); |
| } |
| |
| static int rb_head_page_set_normal(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *head, |
| struct buffer_page *prev, |
| int old_flag) |
| { |
| return rb_head_page_set(cpu_buffer, head, prev, |
| old_flag, RB_PAGE_NORMAL); |
| } |
| |
| static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page **bpage) |
| { |
| struct list_head *p = rb_list_head((*bpage)->list.next); |
| |
| *bpage = list_entry(p, struct buffer_page, list); |
| } |
| |
| static struct buffer_page * |
| rb_set_head_page(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct buffer_page *head; |
| struct buffer_page *page; |
| struct list_head *list; |
| int i; |
| |
| if (RB_WARN_ON(cpu_buffer, !cpu_buffer->head_page)) |
| return NULL; |
| |
| /* sanity check */ |
| list = cpu_buffer->pages; |
| if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev->next) != list)) |
| return NULL; |
| |
| page = head = cpu_buffer->head_page; |
| /* |
| * It is possible that the writer moves the header behind |
| * where we started, and we miss in one loop. |
| * A second loop should grab the header, but we'll do |
| * three loops just because I'm paranoid. |
| */ |
| for (i = 0; i < 3; i++) { |
| do { |
| if (rb_is_head_page(cpu_buffer, page, page->list.prev)) { |
| cpu_buffer->head_page = page; |
| return page; |
| } |
| rb_inc_page(cpu_buffer, &page); |
| } while (page != head); |
| } |
| |
| RB_WARN_ON(cpu_buffer, 1); |
| |
| return NULL; |
| } |
| |
| static int rb_head_page_replace(struct buffer_page *old, |
| struct buffer_page *new) |
| { |
| unsigned long *ptr = (unsigned long *)&old->list.prev->next; |
| unsigned long val; |
| unsigned long ret; |
| |
| val = *ptr & ~RB_FLAG_MASK; |
| val |= RB_PAGE_HEAD; |
| |
| ret = cmpxchg(ptr, val, (unsigned long)&new->list); |
| |
| return ret == val; |
| } |
| |
| /* |
| * rb_tail_page_update - move the tail page forward |
| */ |
| static void rb_tail_page_update(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *tail_page, |
| struct buffer_page *next_page) |
| { |
| unsigned long old_entries; |
| unsigned long old_write; |
| |
| /* |
| * The tail page now needs to be moved forward. |
| * |
| * We need to reset the tail page, but without messing |
| * with possible erasing of data brought in by interrupts |
| * that have moved the tail page and are currently on it. |
| * |
| * We add a counter to the write field to denote this. |
| */ |
| old_write = local_add_return(RB_WRITE_INTCNT, &next_page->write); |
| old_entries = local_add_return(RB_WRITE_INTCNT, &next_page->entries); |
| |
| local_inc(&cpu_buffer->pages_touched); |
| /* |
| * Just make sure we have seen our old_write and synchronize |
| * with any interrupts that come in. |
| */ |
| barrier(); |
| |
| /* |
| * If the tail page is still the same as what we think |
| * it is, then it is up to us to update the tail |
| * pointer. |
| */ |
| if (tail_page == READ_ONCE(cpu_buffer->tail_page)) { |
| /* Zero the write counter */ |
| unsigned long val = old_write & ~RB_WRITE_MASK; |
| unsigned long eval = old_entries & ~RB_WRITE_MASK; |
| |
| /* |
| * This will only succeed if an interrupt did |
| * not come in and change it. In which case, we |
| * do not want to modify it. |
| * |
| * We add (void) to let the compiler know that we do not care |
| * about the return value of these functions. We use the |
| * cmpxchg to only update if an interrupt did not already |
| * do it for us. If the cmpxchg fails, we don't care. |
| */ |
| (void)local_cmpxchg(&next_page->write, old_write, val); |
| (void)local_cmpxchg(&next_page->entries, old_entries, eval); |
| |
| /* |
| * No need to worry about races with clearing out the commit. |
| * it only can increment when a commit takes place. But that |
| * only happens in the outer most nested commit. |
| */ |
| local_set(&next_page->page->commit, 0); |
| |
| /* Again, either we update tail_page or an interrupt does */ |
| (void)cmpxchg(&cpu_buffer->tail_page, tail_page, next_page); |
| } |
| } |
| |
| static int rb_check_bpage(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *bpage) |
| { |
| unsigned long val = (unsigned long)bpage; |
| |
| if (RB_WARN_ON(cpu_buffer, val & RB_FLAG_MASK)) |
| return 1; |
| |
| return 0; |
| } |
| |
| /** |
| * rb_check_list - make sure a pointer to a list has the last bits zero |
| */ |
| static int rb_check_list(struct ring_buffer_per_cpu *cpu_buffer, |
| struct list_head *list) |
| { |
| if (RB_WARN_ON(cpu_buffer, rb_list_head(list->prev) != list->prev)) |
| return 1; |
| if (RB_WARN_ON(cpu_buffer, rb_list_head(list->next) != list->next)) |
| return 1; |
| return 0; |
| } |
| |
| /** |
| * rb_check_pages - integrity check of buffer pages |
| * @cpu_buffer: CPU buffer with pages to test |
| * |
| * As a safety measure we check to make sure the data pages have not |
| * been corrupted. |
| */ |
| static int rb_check_pages(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct list_head *head = cpu_buffer->pages; |
| struct buffer_page *bpage, *tmp; |
| |
| /* Reset the head page if it exists */ |
| if (cpu_buffer->head_page) |
| rb_set_head_page(cpu_buffer); |
| |
| rb_head_page_deactivate(cpu_buffer); |
| |
| if (RB_WARN_ON(cpu_buffer, head->next->prev != head)) |
| return -1; |
| if (RB_WARN_ON(cpu_buffer, head->prev->next != head)) |
| return -1; |
| |
| if (rb_check_list(cpu_buffer, head)) |
| return -1; |
| |
| list_for_each_entry_safe(bpage, tmp, head, list) { |
| if (RB_WARN_ON(cpu_buffer, |
| bpage->list.next->prev != &bpage->list)) |
| return -1; |
| if (RB_WARN_ON(cpu_buffer, |
| bpage->list.prev->next != &bpage->list)) |
| return -1; |
| if (rb_check_list(cpu_buffer, &bpage->list)) |
| return -1; |
| } |
| |
| rb_head_page_activate(cpu_buffer); |
| |
| return 0; |
| } |
| |
| static int __rb_allocate_pages(long nr_pages, struct list_head *pages, int cpu) |
| { |
| struct buffer_page *bpage, *tmp; |
| bool user_thread = current->mm != NULL; |
| gfp_t mflags; |
| long i; |
| |
| /* |
| * Check if the available memory is there first. |
| * Note, si_mem_available() only gives us a rough estimate of available |
| * memory. It may not be accurate. But we don't care, we just want |
| * to prevent doing any allocation when it is obvious that it is |
| * not going to succeed. |
| */ |
| i = si_mem_available(); |
| if (i < nr_pages) |
| return -ENOMEM; |
| |
| /* |
| * __GFP_RETRY_MAYFAIL flag makes sure that the allocation fails |
| * gracefully without invoking oom-killer and the system is not |
| * destabilized. |
| */ |
| mflags = GFP_KERNEL | __GFP_RETRY_MAYFAIL; |
| |
| /* |
| * If a user thread allocates too much, and si_mem_available() |
| * reports there's enough memory, even though there is not. |
| * Make sure the OOM killer kills this thread. This can happen |
| * even with RETRY_MAYFAIL because another task may be doing |
| * an allocation after this task has taken all memory. |
| * This is the task the OOM killer needs to take out during this |
| * loop, even if it was triggered by an allocation somewhere else. |
| */ |
| if (user_thread) |
| set_current_oom_origin(); |
| for (i = 0; i < nr_pages; i++) { |
| struct page *page; |
| |
| bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
| mflags, cpu_to_node(cpu)); |
| if (!bpage) |
| goto free_pages; |
| |
| list_add(&bpage->list, pages); |
| |
| page = alloc_pages_node(cpu_to_node(cpu), mflags, 0); |
| if (!page) |
| goto free_pages; |
| bpage->page = page_address(page); |
| rb_init_page(bpage->page); |
| |
| if (user_thread && fatal_signal_pending(current)) |
| goto free_pages; |
| } |
| if (user_thread) |
| clear_current_oom_origin(); |
| |
| return 0; |
| |
| free_pages: |
| list_for_each_entry_safe(bpage, tmp, pages, list) { |
| list_del_init(&bpage->list); |
| free_buffer_page(bpage); |
| } |
| if (user_thread) |
| clear_current_oom_origin(); |
| |
| return -ENOMEM; |
| } |
| |
| static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer, |
| unsigned long nr_pages) |
| { |
| LIST_HEAD(pages); |
| |
| WARN_ON(!nr_pages); |
| |
| if (__rb_allocate_pages(nr_pages, &pages, cpu_buffer->cpu)) |
| return -ENOMEM; |
| |
| /* |
| * The ring buffer page list is a circular list that does not |
| * start and end with a list head. All page list items point to |
| * other pages. |
| */ |
| cpu_buffer->pages = pages.next; |
| list_del(&pages); |
| |
| cpu_buffer->nr_pages = nr_pages; |
| |
| rb_check_pages(cpu_buffer); |
| |
| return 0; |
| } |
| |
| static struct ring_buffer_per_cpu * |
| rb_allocate_cpu_buffer(struct ring_buffer *buffer, long nr_pages, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| struct buffer_page *bpage; |
| struct page *page; |
| int ret; |
| |
| cpu_buffer = kzalloc_node(ALIGN(sizeof(*cpu_buffer), cache_line_size()), |
| GFP_KERNEL, cpu_to_node(cpu)); |
| if (!cpu_buffer) |
| return NULL; |
| |
| cpu_buffer->cpu = cpu; |
| cpu_buffer->buffer = buffer; |
| raw_spin_lock_init(&cpu_buffer->reader_lock); |
| lockdep_set_class(&cpu_buffer->reader_lock, buffer->reader_lock_key); |
| cpu_buffer->lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; |
| INIT_WORK(&cpu_buffer->update_pages_work, update_pages_handler); |
| init_completion(&cpu_buffer->update_done); |
| init_irq_work(&cpu_buffer->irq_work.work, rb_wake_up_waiters); |
| init_waitqueue_head(&cpu_buffer->irq_work.waiters); |
| init_waitqueue_head(&cpu_buffer->irq_work.full_waiters); |
| |
| bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()), |
| GFP_KERNEL, cpu_to_node(cpu)); |
| if (!bpage) |
| goto fail_free_buffer; |
| |
| rb_check_bpage(cpu_buffer, bpage); |
| |
| cpu_buffer->reader_page = bpage; |
| page = alloc_pages_node(cpu_to_node(cpu), GFP_KERNEL, 0); |
| if (!page) |
| goto fail_free_reader; |
| bpage->page = page_address(page); |
| rb_init_page(bpage->page); |
| |
| INIT_LIST_HEAD(&cpu_buffer->reader_page->list); |
| INIT_LIST_HEAD(&cpu_buffer->new_pages); |
| |
| ret = rb_allocate_pages(cpu_buffer, nr_pages); |
| if (ret < 0) |
| goto fail_free_reader; |
| |
| cpu_buffer->head_page |
| = list_entry(cpu_buffer->pages, struct buffer_page, list); |
| cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page; |
| |
| rb_head_page_activate(cpu_buffer); |
| |
| return cpu_buffer; |
| |
| fail_free_reader: |
| free_buffer_page(cpu_buffer->reader_page); |
| |
| fail_free_buffer: |
| kfree(cpu_buffer); |
| return NULL; |
| } |
| |
| static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct list_head *head = cpu_buffer->pages; |
| struct buffer_page *bpage, *tmp; |
| |
| free_buffer_page(cpu_buffer->reader_page); |
| |
| rb_head_page_deactivate(cpu_buffer); |
| |
| if (head) { |
| list_for_each_entry_safe(bpage, tmp, head, list) { |
| list_del_init(&bpage->list); |
| free_buffer_page(bpage); |
| } |
| bpage = list_entry(head, struct buffer_page, list); |
| free_buffer_page(bpage); |
| } |
| |
| kfree(cpu_buffer); |
| } |
| |
| /** |
| * __ring_buffer_alloc - allocate a new ring_buffer |
| * @size: the size in bytes per cpu that is needed. |
| * @flags: attributes to set for the ring buffer. |
| * |
| * Currently the only flag that is available is the RB_FL_OVERWRITE |
| * flag. This flag means that the buffer will overwrite old data |
| * when the buffer wraps. If this flag is not set, the buffer will |
| * drop data when the tail hits the head. |
| */ |
| struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, |
| struct lock_class_key *key) |
| { |
| struct ring_buffer *buffer; |
| long nr_pages; |
| int bsize; |
| int cpu; |
| int ret; |
| |
| /* keep it in its own cache line */ |
| buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()), |
| GFP_KERNEL); |
| if (!buffer) |
| return NULL; |
| |
| if (!zalloc_cpumask_var(&buffer->cpumask, GFP_KERNEL)) |
| goto fail_free_buffer; |
| |
| nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
| buffer->flags = flags; |
| buffer->clock = trace_clock_local; |
| buffer->reader_lock_key = key; |
| |
| init_irq_work(&buffer->irq_work.work, rb_wake_up_waiters); |
| init_waitqueue_head(&buffer->irq_work.waiters); |
| |
| /* need at least two pages */ |
| if (nr_pages < 2) |
| nr_pages = 2; |
| |
| buffer->cpus = nr_cpu_ids; |
| |
| bsize = sizeof(void *) * nr_cpu_ids; |
| buffer->buffers = kzalloc(ALIGN(bsize, cache_line_size()), |
| GFP_KERNEL); |
| if (!buffer->buffers) |
| goto fail_free_cpumask; |
| |
| cpu = raw_smp_processor_id(); |
| cpumask_set_cpu(cpu, buffer->cpumask); |
| buffer->buffers[cpu] = rb_allocate_cpu_buffer(buffer, nr_pages, cpu); |
| if (!buffer->buffers[cpu]) |
| goto fail_free_buffers; |
| |
| ret = cpuhp_state_add_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
| if (ret < 0) |
| goto fail_free_buffers; |
| |
| mutex_init(&buffer->mutex); |
| |
| return buffer; |
| |
| fail_free_buffers: |
| for_each_buffer_cpu(buffer, cpu) { |
| if (buffer->buffers[cpu]) |
| rb_free_cpu_buffer(buffer->buffers[cpu]); |
| } |
| kfree(buffer->buffers); |
| |
| fail_free_cpumask: |
| free_cpumask_var(buffer->cpumask); |
| |
| fail_free_buffer: |
| kfree(buffer); |
| return NULL; |
| } |
| EXPORT_SYMBOL_GPL(__ring_buffer_alloc); |
| |
| /** |
| * ring_buffer_free - free a ring buffer. |
| * @buffer: the buffer to free. |
| */ |
| void |
| ring_buffer_free(struct ring_buffer *buffer) |
| { |
| int cpu; |
| |
| cpuhp_state_remove_instance(CPUHP_TRACE_RB_PREPARE, &buffer->node); |
| |
| for_each_buffer_cpu(buffer, cpu) |
| rb_free_cpu_buffer(buffer->buffers[cpu]); |
| |
| kfree(buffer->buffers); |
| free_cpumask_var(buffer->cpumask); |
| |
| kfree(buffer); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_free); |
| |
| void ring_buffer_set_clock(struct ring_buffer *buffer, |
| u64 (*clock)(void)) |
| { |
| buffer->clock = clock; |
| } |
| |
| void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs) |
| { |
| buffer->time_stamp_abs = abs; |
| } |
| |
| bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer) |
| { |
| return buffer->time_stamp_abs; |
| } |
| |
| static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer); |
| |
| static inline unsigned long rb_page_entries(struct buffer_page *bpage) |
| { |
| return local_read(&bpage->entries) & RB_WRITE_MASK; |
| } |
| |
| static inline unsigned long rb_page_write(struct buffer_page *bpage) |
| { |
| return local_read(&bpage->write) & RB_WRITE_MASK; |
| } |
| |
| static int |
| rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned long nr_pages) |
| { |
| struct list_head *tail_page, *to_remove, *next_page; |
| struct buffer_page *to_remove_page, *tmp_iter_page; |
| struct buffer_page *last_page, *first_page; |
| unsigned long nr_removed; |
| unsigned long head_bit; |
| int page_entries; |
| |
| head_bit = 0; |
| |
| raw_spin_lock_irq(&cpu_buffer->reader_lock); |
| atomic_inc(&cpu_buffer->record_disabled); |
| /* |
| * We don't race with the readers since we have acquired the reader |
| * lock. We also don't race with writers after disabling recording. |
| * This makes it easy to figure out the first and the last page to be |
| * removed from the list. We unlink all the pages in between including |
| * the first and last pages. This is done in a busy loop so that we |
| * lose the least number of traces. |
| * The pages are freed after we restart recording and unlock readers. |
| */ |
| tail_page = &cpu_buffer->tail_page->list; |
| |
| /* |
| * tail page might be on reader page, we remove the next page |
| * from the ring buffer |
| */ |
| if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
| tail_page = rb_list_head(tail_page->next); |
| to_remove = tail_page; |
| |
| /* start of pages to remove */ |
| first_page = list_entry(rb_list_head(to_remove->next), |
| struct buffer_page, list); |
| |
| for (nr_removed = 0; nr_removed < nr_pages; nr_removed++) { |
| to_remove = rb_list_head(to_remove)->next; |
| head_bit |= (unsigned long)to_remove & RB_PAGE_HEAD; |
| } |
| |
| next_page = rb_list_head(to_remove)->next; |
| |
| /* |
| * Now we remove all pages between tail_page and next_page. |
| * Make sure that we have head_bit value preserved for the |
| * next page |
| */ |
| tail_page->next = (struct list_head *)((unsigned long)next_page | |
| head_bit); |
| next_page = rb_list_head(next_page); |
| next_page->prev = tail_page; |
| |
| /* make sure pages points to a valid page in the ring buffer */ |
| cpu_buffer->pages = next_page; |
| |
| /* update head page */ |
| if (head_bit) |
| cpu_buffer->head_page = list_entry(next_page, |
| struct buffer_page, list); |
| |
| /* |
| * change read pointer to make sure any read iterators reset |
| * themselves |
| */ |
| cpu_buffer->read = 0; |
| |
| /* pages are removed, resume tracing and then free the pages */ |
| atomic_dec(&cpu_buffer->record_disabled); |
| raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
| |
| RB_WARN_ON(cpu_buffer, list_empty(cpu_buffer->pages)); |
| |
| /* last buffer page to remove */ |
| last_page = list_entry(rb_list_head(to_remove), struct buffer_page, |
| list); |
| tmp_iter_page = first_page; |
| |
| do { |
| cond_resched(); |
| |
| to_remove_page = tmp_iter_page; |
| rb_inc_page(cpu_buffer, &tmp_iter_page); |
| |
| /* update the counters */ |
| page_entries = rb_page_entries(to_remove_page); |
| if (page_entries) { |
| /* |
| * If something was added to this page, it was full |
| * since it is not the tail page. So we deduct the |
| * bytes consumed in ring buffer from here. |
| * Increment overrun to account for the lost events. |
| */ |
| local_add(page_entries, &cpu_buffer->overrun); |
| local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
| } |
| |
| /* |
| * We have already removed references to this list item, just |
| * free up the buffer_page and its page |
| */ |
| free_buffer_page(to_remove_page); |
| nr_removed--; |
| |
| } while (to_remove_page != last_page); |
| |
| RB_WARN_ON(cpu_buffer, nr_removed); |
| |
| return nr_removed == 0; |
| } |
| |
| static int |
| rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct list_head *pages = &cpu_buffer->new_pages; |
| int retries, success; |
| |
| raw_spin_lock_irq(&cpu_buffer->reader_lock); |
| /* |
| * We are holding the reader lock, so the reader page won't be swapped |
| * in the ring buffer. Now we are racing with the writer trying to |
| * move head page and the tail page. |
| * We are going to adapt the reader page update process where: |
| * 1. We first splice the start and end of list of new pages between |
| * the head page and its previous page. |
| * 2. We cmpxchg the prev_page->next to point from head page to the |
| * start of new pages list. |
| * 3. Finally, we update the head->prev to the end of new list. |
| * |
| * We will try this process 10 times, to make sure that we don't keep |
| * spinning. |
| */ |
| retries = 10; |
| success = 0; |
| while (retries--) { |
| struct list_head *head_page, *prev_page, *r; |
| struct list_head *last_page, *first_page; |
| struct list_head *head_page_with_bit; |
| |
| head_page = &rb_set_head_page(cpu_buffer)->list; |
| if (!head_page) |
| break; |
| prev_page = head_page->prev; |
| |
| first_page = pages->next; |
| last_page = pages->prev; |
| |
| head_page_with_bit = (struct list_head *) |
| ((unsigned long)head_page | RB_PAGE_HEAD); |
| |
| last_page->next = head_page_with_bit; |
| first_page->prev = prev_page; |
| |
| r = cmpxchg(&prev_page->next, head_page_with_bit, first_page); |
| |
| if (r == head_page_with_bit) { |
| /* |
| * yay, we replaced the page pointer to our new list, |
| * now, we just have to update to head page's prev |
| * pointer to point to end of list |
| */ |
| head_page->prev = last_page; |
| success = 1; |
| break; |
| } |
| } |
| |
| if (success) |
| INIT_LIST_HEAD(pages); |
| /* |
| * If we weren't successful in adding in new pages, warn and stop |
| * tracing |
| */ |
| RB_WARN_ON(cpu_buffer, !success); |
| raw_spin_unlock_irq(&cpu_buffer->reader_lock); |
| |
| /* free pages if they weren't inserted */ |
| if (!success) { |
| struct buffer_page *bpage, *tmp; |
| list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
| list) { |
| list_del_init(&bpage->list); |
| free_buffer_page(bpage); |
| } |
| } |
| return success; |
| } |
| |
| static void rb_update_pages(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| int success; |
| |
| if (cpu_buffer->nr_pages_to_update > 0) |
| success = rb_insert_pages(cpu_buffer); |
| else |
| success = rb_remove_pages(cpu_buffer, |
| -cpu_buffer->nr_pages_to_update); |
| |
| if (success) |
| cpu_buffer->nr_pages += cpu_buffer->nr_pages_to_update; |
| } |
| |
| static void update_pages_handler(struct work_struct *work) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer = container_of(work, |
| struct ring_buffer_per_cpu, update_pages_work); |
| rb_update_pages(cpu_buffer); |
| complete(&cpu_buffer->update_done); |
| } |
| |
| /** |
| * ring_buffer_resize - resize the ring buffer |
| * @buffer: the buffer to resize. |
| * @size: the new size. |
| * @cpu_id: the cpu buffer to resize |
| * |
| * Minimum size is 2 * BUF_PAGE_SIZE. |
| * |
| * Returns 0 on success and < 0 on failure. |
| */ |
| int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size, |
| int cpu_id) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| unsigned long nr_pages; |
| int cpu, err = 0; |
| |
| /* |
| * Always succeed at resizing a non-existent buffer: |
| */ |
| if (!buffer) |
| return size; |
| |
| /* Make sure the requested buffer exists */ |
| if (cpu_id != RING_BUFFER_ALL_CPUS && |
| !cpumask_test_cpu(cpu_id, buffer->cpumask)) |
| return size; |
| |
| nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE); |
| |
| /* we need a minimum of two pages */ |
| if (nr_pages < 2) |
| nr_pages = 2; |
| |
| size = nr_pages * BUF_PAGE_SIZE; |
| |
| /* |
| * Don't succeed if resizing is disabled, as a reader might be |
| * manipulating the ring buffer and is expecting a sane state while |
| * this is true. |
| */ |
| if (atomic_read(&buffer->resize_disabled)) |
| return -EBUSY; |
| |
| /* prevent another thread from changing buffer sizes */ |
| mutex_lock(&buffer->mutex); |
| |
| if (cpu_id == RING_BUFFER_ALL_CPUS) { |
| /* calculate the pages to update */ |
| for_each_buffer_cpu(buffer, cpu) { |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| cpu_buffer->nr_pages_to_update = nr_pages - |
| cpu_buffer->nr_pages; |
| /* |
| * nothing more to do for removing pages or no update |
| */ |
| if (cpu_buffer->nr_pages_to_update <= 0) |
| continue; |
| /* |
| * to add pages, make sure all new pages can be |
| * allocated without receiving ENOMEM |
| */ |
| INIT_LIST_HEAD(&cpu_buffer->new_pages); |
| if (__rb_allocate_pages(cpu_buffer->nr_pages_to_update, |
| &cpu_buffer->new_pages, cpu)) { |
| /* not enough memory for new pages */ |
| err = -ENOMEM; |
| goto out_err; |
| } |
| } |
| |
| get_online_cpus(); |
| /* |
| * Fire off all the required work handlers |
| * We can't schedule on offline CPUs, but it's not necessary |
| * since we can change their buffer sizes without any race. |
| */ |
| for_each_buffer_cpu(buffer, cpu) { |
| cpu_buffer = buffer->buffers[cpu]; |
| if (!cpu_buffer->nr_pages_to_update) |
| continue; |
| |
| /* Can't run something on an offline CPU. */ |
| if (!cpu_online(cpu)) { |
| rb_update_pages(cpu_buffer); |
| cpu_buffer->nr_pages_to_update = 0; |
| } else { |
| schedule_work_on(cpu, |
| &cpu_buffer->update_pages_work); |
| } |
| } |
| |
| /* wait for all the updates to complete */ |
| for_each_buffer_cpu(buffer, cpu) { |
| cpu_buffer = buffer->buffers[cpu]; |
| if (!cpu_buffer->nr_pages_to_update) |
| continue; |
| |
| if (cpu_online(cpu)) |
| wait_for_completion(&cpu_buffer->update_done); |
| cpu_buffer->nr_pages_to_update = 0; |
| } |
| |
| put_online_cpus(); |
| } else { |
| /* Make sure this CPU has been initialized */ |
| if (!cpumask_test_cpu(cpu_id, buffer->cpumask)) |
| goto out; |
| |
| cpu_buffer = buffer->buffers[cpu_id]; |
| |
| if (nr_pages == cpu_buffer->nr_pages) |
| goto out; |
| |
| cpu_buffer->nr_pages_to_update = nr_pages - |
| cpu_buffer->nr_pages; |
| |
| INIT_LIST_HEAD(&cpu_buffer->new_pages); |
| if (cpu_buffer->nr_pages_to_update > 0 && |
| __rb_allocate_pages(cpu_buffer->nr_pages_to_update, |
| &cpu_buffer->new_pages, cpu_id)) { |
| err = -ENOMEM; |
| goto out_err; |
| } |
| |
| get_online_cpus(); |
| |
| /* Can't run something on an offline CPU. */ |
| if (!cpu_online(cpu_id)) |
| rb_update_pages(cpu_buffer); |
| else { |
| schedule_work_on(cpu_id, |
| &cpu_buffer->update_pages_work); |
| wait_for_completion(&cpu_buffer->update_done); |
| } |
| |
| cpu_buffer->nr_pages_to_update = 0; |
| put_online_cpus(); |
| } |
| |
| out: |
| /* |
| * The ring buffer resize can happen with the ring buffer |
| * enabled, so that the update disturbs the tracing as little |
| * as possible. But if the buffer is disabled, we do not need |
| * to worry about that, and we can take the time to verify |
| * that the buffer is not corrupt. |
| */ |
| if (atomic_read(&buffer->record_disabled)) { |
| atomic_inc(&buffer->record_disabled); |
| /* |
| * Even though the buffer was disabled, we must make sure |
| * that it is truly disabled before calling rb_check_pages. |
| * There could have been a race between checking |
| * record_disable and incrementing it. |
| */ |
| synchronize_rcu(); |
| for_each_buffer_cpu(buffer, cpu) { |
| cpu_buffer = buffer->buffers[cpu]; |
| rb_check_pages(cpu_buffer); |
| } |
| atomic_dec(&buffer->record_disabled); |
| } |
| |
| mutex_unlock(&buffer->mutex); |
| return size; |
| |
| out_err: |
| for_each_buffer_cpu(buffer, cpu) { |
| struct buffer_page *bpage, *tmp; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| cpu_buffer->nr_pages_to_update = 0; |
| |
| if (list_empty(&cpu_buffer->new_pages)) |
| continue; |
| |
| list_for_each_entry_safe(bpage, tmp, &cpu_buffer->new_pages, |
| list) { |
| list_del_init(&bpage->list); |
| free_buffer_page(bpage); |
| } |
| } |
| mutex_unlock(&buffer->mutex); |
| return err; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_resize); |
| |
| void ring_buffer_change_overwrite(struct ring_buffer *buffer, int val) |
| { |
| mutex_lock(&buffer->mutex); |
| if (val) |
| buffer->flags |= RB_FL_OVERWRITE; |
| else |
| buffer->flags &= ~RB_FL_OVERWRITE; |
| mutex_unlock(&buffer->mutex); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_change_overwrite); |
| |
| static __always_inline void *__rb_page_index(struct buffer_page *bpage, unsigned index) |
| { |
| return bpage->page->data + index; |
| } |
| |
| static __always_inline struct ring_buffer_event * |
| rb_reader_event(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| return __rb_page_index(cpu_buffer->reader_page, |
| cpu_buffer->reader_page->read); |
| } |
| |
| static __always_inline struct ring_buffer_event * |
| rb_iter_head_event(struct ring_buffer_iter *iter) |
| { |
| return __rb_page_index(iter->head_page, iter->head); |
| } |
| |
| static __always_inline unsigned rb_page_commit(struct buffer_page *bpage) |
| { |
| return local_read(&bpage->page->commit); |
| } |
| |
| /* Size is determined by what has been committed */ |
| static __always_inline unsigned rb_page_size(struct buffer_page *bpage) |
| { |
| return rb_page_commit(bpage); |
| } |
| |
| static __always_inline unsigned |
| rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| return rb_page_commit(cpu_buffer->commit_page); |
| } |
| |
| static __always_inline unsigned |
| rb_event_index(struct ring_buffer_event *event) |
| { |
| unsigned long addr = (unsigned long)event; |
| |
| return (addr & ~PAGE_MASK) - BUF_PAGE_HDR_SIZE; |
| } |
| |
| static void rb_inc_iter(struct ring_buffer_iter *iter) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer; |
| |
| /* |
| * The iterator could be on the reader page (it starts there). |
| * But the head could have moved, since the reader was |
| * found. Check for this case and assign the iterator |
| * to the head page instead of next. |
| */ |
| if (iter->head_page == cpu_buffer->reader_page) |
| iter->head_page = rb_set_head_page(cpu_buffer); |
| else |
| rb_inc_page(cpu_buffer, &iter->head_page); |
| |
| iter->read_stamp = iter->head_page->page->time_stamp; |
| iter->head = 0; |
| } |
| |
| /* |
| * rb_handle_head_page - writer hit the head page |
| * |
| * Returns: +1 to retry page |
| * 0 to continue |
| * -1 on error |
| */ |
| static int |
| rb_handle_head_page(struct ring_buffer_per_cpu *cpu_buffer, |
| struct buffer_page *tail_page, |
| struct buffer_page *next_page) |
| { |
| struct buffer_page *new_head; |
| int entries; |
| int type; |
| int ret; |
| |
| entries = rb_page_entries(next_page); |
| |
| /* |
| * The hard part is here. We need to move the head |
| * forward, and protect against both readers on |
| * other CPUs and writers coming in via interrupts. |
| */ |
| type = rb_head_page_set_update(cpu_buffer, next_page, tail_page, |
| RB_PAGE_HEAD); |
| |
| /* |
| * type can be one of four: |
| * NORMAL - an interrupt already moved it for us |
| * HEAD - we are the first to get here. |
| * UPDATE - we are the interrupt interrupting |
| * a current move. |
| * MOVED - a reader on another CPU moved the next |
| * pointer to its reader page. Give up |
| * and try again. |
| */ |
| |
| switch (type) { |
| case RB_PAGE_HEAD: |
| /* |
| * We changed the head to UPDATE, thus |
| * it is our responsibility to update |
| * the counters. |
| */ |
| local_add(entries, &cpu_buffer->overrun); |
| local_sub(BUF_PAGE_SIZE, &cpu_buffer->entries_bytes); |
| |
| /* |
| * The entries will be zeroed out when we move the |
| * tail page. |
| */ |
| |
| /* still more to do */ |
| break; |
| |
| case RB_PAGE_UPDATE: |
| /* |
| * This is an interrupt that interrupt the |
| * previous update. Still more to do. |
| */ |
| break; |
| case RB_PAGE_NORMAL: |
| /* |
| * An interrupt came in before the update |
| * and processed this for us. |
| * Nothing left to do. |
| */ |
| return 1; |
| case RB_PAGE_MOVED: |
| /* |
| * The reader is on another CPU and just did |
| * a swap with our next_page. |
| * Try again. |
| */ |
| return 1; |
| default: |
| RB_WARN_ON(cpu_buffer, 1); /* WTF??? */ |
| return -1; |
| } |
| |
| /* |
| * Now that we are here, the old head pointer is |
| * set to UPDATE. This will keep the reader from |
| * swapping the head page with the reader page. |
| * The reader (on another CPU) will spin till |
| * we are finished. |
| * |
| * We just need to protect against interrupts |
| * doing the job. We will set the next pointer |
| * to HEAD. After that, we set the old pointer |
| * to NORMAL, but only if it was HEAD before. |
| * otherwise we are an interrupt, and only |
| * want the outer most commit to reset it. |
| */ |
| new_head = next_page; |
| rb_inc_page(cpu_buffer, &new_head); |
| |
| ret = rb_head_page_set_head(cpu_buffer, new_head, next_page, |
| RB_PAGE_NORMAL); |
| |
| /* |
| * Valid returns are: |
| * HEAD - an interrupt came in and already set it. |
| * NORMAL - One of two things: |
| * 1) We really set it. |
| * 2) A bunch of interrupts came in and moved |
| * the page forward again. |
| */ |
| switch (ret) { |
| case RB_PAGE_HEAD: |
| case RB_PAGE_NORMAL: |
| /* OK */ |
| break; |
| default: |
| RB_WARN_ON(cpu_buffer, 1); |
| return -1; |
| } |
| |
| /* |
| * It is possible that an interrupt came in, |
| * set the head up, then more interrupts came in |
| * and moved it again. When we get back here, |
| * the page would have been set to NORMAL but we |
| * just set it back to HEAD. |
| * |
| * How do you detect this? Well, if that happened |
| * the tail page would have moved. |
| */ |
| if (ret == RB_PAGE_NORMAL) { |
| struct buffer_page *buffer_tail_page; |
| |
| buffer_tail_page = READ_ONCE(cpu_buffer->tail_page); |
| /* |
| * If the tail had moved passed next, then we need |
| * to reset the pointer. |
| */ |
| if (buffer_tail_page != tail_page && |
| buffer_tail_page != next_page) |
| rb_head_page_set_normal(cpu_buffer, new_head, |
| next_page, |
| RB_PAGE_HEAD); |
| } |
| |
| /* |
| * If this was the outer most commit (the one that |
| * changed the original pointer from HEAD to UPDATE), |
| * then it is up to us to reset it to NORMAL. |
| */ |
| if (type == RB_PAGE_HEAD) { |
| ret = rb_head_page_set_normal(cpu_buffer, next_page, |
| tail_page, |
| RB_PAGE_UPDATE); |
| if (RB_WARN_ON(cpu_buffer, |
| ret != RB_PAGE_UPDATE)) |
| return -1; |
| } |
| |
| return 0; |
| } |
| |
| static inline void |
| rb_reset_tail(struct ring_buffer_per_cpu *cpu_buffer, |
| unsigned long tail, struct rb_event_info *info) |
| { |
| struct buffer_page *tail_page = info->tail_page; |
| struct ring_buffer_event *event; |
| unsigned long length = info->length; |
| |
| /* |
| * Only the event that crossed the page boundary |
| * must fill the old tail_page with padding. |
| */ |
| if (tail >= BUF_PAGE_SIZE) { |
| /* |
| * If the page was filled, then we still need |
| * to update the real_end. Reset it to zero |
| * and the reader will ignore it. |
| */ |
| if (tail == BUF_PAGE_SIZE) |
| tail_page->real_end = 0; |
| |
| local_sub(length, &tail_page->write); |
| return; |
| } |
| |
| event = __rb_page_index(tail_page, tail); |
| |
| /* account for padding bytes */ |
| local_add(BUF_PAGE_SIZE - tail, &cpu_buffer->entries_bytes); |
| |
| /* |
| * Save the original length to the meta data. |
| * This will be used by the reader to add lost event |
| * counter. |
| */ |
| tail_page->real_end = tail; |
| |
| /* |
| * If this event is bigger than the minimum size, then |
| * we need to be careful that we don't subtract the |
| * write counter enough to allow another writer to slip |
| * in on this page. |
| * We put in a discarded commit instead, to make sure |
| * that this space is not used again. |
| * |
| * If we are less than the minimum size, we don't need to |
| * worry about it. |
| */ |
| if (tail > (BUF_PAGE_SIZE - RB_EVNT_MIN_SIZE)) { |
| /* No room for any events */ |
| |
| /* Mark the rest of the page with padding */ |
| rb_event_set_padding(event); |
| |
| /* Set the write back to the previous setting */ |
| local_sub(length, &tail_page->write); |
| return; |
| } |
| |
| /* Put in a discarded event */ |
| event->array[0] = (BUF_PAGE_SIZE - tail) - RB_EVNT_HDR_SIZE; |
| event->type_len = RINGBUF_TYPE_PADDING; |
| /* time delta must be non zero */ |
| event->time_delta = 1; |
| |
| /* Set write to end of buffer */ |
| length = (tail + length) - BUF_PAGE_SIZE; |
| local_sub(length, &tail_page->write); |
| } |
| |
| static inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer); |
| |
| /* |
| * This is the slow path, force gcc not to inline it. |
| */ |
| static noinline struct ring_buffer_event * |
| rb_move_tail(struct ring_buffer_per_cpu *cpu_buffer, |
| unsigned long tail, struct rb_event_info *info) |
| { |
| struct buffer_page *tail_page = info->tail_page; |
| struct buffer_page *commit_page = cpu_buffer->commit_page; |
| struct ring_buffer *buffer = cpu_buffer->buffer; |
| struct buffer_page *next_page; |
| int ret; |
| |
| next_page = tail_page; |
| |
| rb_inc_page(cpu_buffer, &next_page); |
| |
| /* |
| * If for some reason, we had an interrupt storm that made |
| * it all the way around the buffer, bail, and warn |
| * about it. |
| */ |
| if (unlikely(next_page == commit_page)) { |
| local_inc(&cpu_buffer->commit_overrun); |
| goto out_reset; |
| } |
| |
| /* |
| * This is where the fun begins! |
| * |
| * We are fighting against races between a reader that |
| * could be on another CPU trying to swap its reader |
| * page with the buffer head. |
| * |
| * We are also fighting against interrupts coming in and |
| * moving the head or tail on us as well. |
| * |
| * If the next page is the head page then we have filled |
| * the buffer, unless the commit page is still on the |
| * reader page. |
| */ |
| if (rb_is_head_page(cpu_buffer, next_page, &tail_page->list)) { |
| |
| /* |
| * If the commit is not on the reader page, then |
| * move the header page. |
| */ |
| if (!rb_is_reader_page(cpu_buffer->commit_page)) { |
| /* |
| * If we are not in overwrite mode, |
| * this is easy, just stop here. |
| */ |
| if (!(buffer->flags & RB_FL_OVERWRITE)) { |
| local_inc(&cpu_buffer->dropped_events); |
| goto out_reset; |
| } |
| |
| ret = rb_handle_head_page(cpu_buffer, |
| tail_page, |
| next_page); |
| if (ret < 0) |
| goto out_reset; |
| if (ret) |
| goto out_again; |
| } else { |
| /* |
| * We need to be careful here too. The |
| * commit page could still be on the reader |
| * page. We could have a small buffer, and |
| * have filled up the buffer with events |
| * from interrupts and such, and wrapped. |
| * |
| * Note, if the tail page is also the on the |
| * reader_page, we let it move out. |
| */ |
| if (unlikely((cpu_buffer->commit_page != |
| cpu_buffer->tail_page) && |
| (cpu_buffer->commit_page == |
| cpu_buffer->reader_page))) { |
| local_inc(&cpu_buffer->commit_overrun); |
| goto out_reset; |
| } |
| } |
| } |
| |
| rb_tail_page_update(cpu_buffer, tail_page, next_page); |
| |
| out_again: |
| |
| rb_reset_tail(cpu_buffer, tail, info); |
| |
| /* Commit what we have for now. */ |
| rb_end_commit(cpu_buffer); |
| /* rb_end_commit() decs committing */ |
| local_inc(&cpu_buffer->committing); |
| |
| /* fail and let the caller try again */ |
| return ERR_PTR(-EAGAIN); |
| |
| out_reset: |
| /* reset write */ |
| rb_reset_tail(cpu_buffer, tail, info); |
| |
| return NULL; |
| } |
| |
| /* Slow path, do not inline */ |
| static noinline struct ring_buffer_event * |
| rb_add_time_stamp(struct ring_buffer_event *event, u64 delta, bool abs) |
| { |
| if (abs) |
| event->type_len = RINGBUF_TYPE_TIME_STAMP; |
| else |
| event->type_len = RINGBUF_TYPE_TIME_EXTEND; |
| |
| /* Not the first event on the page, or not delta? */ |
| if (abs || rb_event_index(event)) { |
| event->time_delta = delta & TS_MASK; |
| event->array[0] = delta >> TS_SHIFT; |
| } else { |
| /* nope, just zero it */ |
| event->time_delta = 0; |
| event->array[0] = 0; |
| } |
| |
| return skip_time_extend(event); |
| } |
| |
| static inline bool rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event); |
| |
| /** |
| * rb_update_event - update event type and data |
| * @event: the event to update |
| * @type: the type of event |
| * @length: the size of the event field in the ring buffer |
| * |
| * Update the type and data fields of the event. The length |
| * is the actual size that is written to the ring buffer, |
| * and with this, we can determine what to place into the |
| * data field. |
| */ |
| static void |
| rb_update_event(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event, |
| struct rb_event_info *info) |
| { |
| unsigned length = info->length; |
| u64 delta = info->delta; |
| |
| /* Only a commit updates the timestamp */ |
| if (unlikely(!rb_event_is_commit(cpu_buffer, event))) |
| delta = 0; |
| |
| /* |
| * If we need to add a timestamp, then we |
| * add it to the start of the reserved space. |
| */ |
| if (unlikely(info->add_timestamp)) { |
| bool abs = ring_buffer_time_stamp_abs(cpu_buffer->buffer); |
| |
| event = rb_add_time_stamp(event, info->delta, abs); |
| length -= RB_LEN_TIME_EXTEND; |
| delta = 0; |
| } |
| |
| event->time_delta = delta; |
| length -= RB_EVNT_HDR_SIZE; |
| if (length > RB_MAX_SMALL_DATA) { |
| event->type_len = 0; |
| event->array[0] = length; |
| } else |
| event->type_len = DIV_ROUND_UP(length, RB_ALIGNMENT); |
| } |
| |
| static unsigned rb_calculate_event_length(unsigned length) |
| { |
| struct ring_buffer_event event; /* Used only for sizeof array */ |
| |
| /* zero length can cause confusions */ |
| if (!length) |
| length++; |
| |
| if (length > RB_MAX_SMALL_DATA) |
| length += sizeof(event.array[0]); |
| |
| length += RB_EVNT_HDR_SIZE; |
| length = ALIGN(length, RB_ALIGNMENT); |
| |
| /* |
| * In case the time delta is larger than the 27 bits for it |
| * in the header, we need to add a timestamp. If another |
| * event comes in when trying to discard this one to increase |
| * the length, then the timestamp will be added in the allocated |
| * space of this event. If length is bigger than the size needed |
| * for the TIME_EXTEND, then padding has to be used. The events |
| * length must be either RB_LEN_TIME_EXTEND, or greater than or equal |
| * to RB_LEN_TIME_EXTEND + 8, as 8 is the minimum size for padding. |
| * As length is a multiple of 4, we only need to worry if it |
| * is 12 (RB_LEN_TIME_EXTEND + 4). |
| */ |
| if (length == RB_LEN_TIME_EXTEND + RB_ALIGNMENT) |
| length += RB_ALIGNMENT; |
| |
| return length; |
| } |
| |
| #ifndef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK |
| static inline bool sched_clock_stable(void) |
| { |
| return true; |
| } |
| #endif |
| |
| static inline int |
| rb_try_to_discard(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event) |
| { |
| unsigned long new_index, old_index; |
| struct buffer_page *bpage; |
| unsigned long index; |
| unsigned long addr; |
| |
| new_index = rb_event_index(event); |
| old_index = new_index + rb_event_ts_length(event); |
| addr = (unsigned long)event; |
| addr &= PAGE_MASK; |
| |
| bpage = READ_ONCE(cpu_buffer->tail_page); |
| |
| if (bpage->page == (void *)addr && rb_page_write(bpage) == old_index) { |
| unsigned long write_mask = |
| local_read(&bpage->write) & ~RB_WRITE_MASK; |
| unsigned long event_length = rb_event_length(event); |
| /* |
| * This is on the tail page. It is possible that |
| * a write could come in and move the tail page |
| * and write to the next page. That is fine |
| * because we just shorten what is on this page. |
| */ |
| old_index += write_mask; |
| new_index += write_mask; |
| index = local_cmpxchg(&bpage->write, old_index, new_index); |
| if (index == old_index) { |
| /* update counters */ |
| local_sub(event_length, &cpu_buffer->entries_bytes); |
| return 1; |
| } |
| } |
| |
| /* could not discard */ |
| return 0; |
| } |
| |
| static void rb_start_commit(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| local_inc(&cpu_buffer->committing); |
| local_inc(&cpu_buffer->commits); |
| } |
| |
| static __always_inline void |
| rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| unsigned long max_count; |
| |
| /* |
| * We only race with interrupts and NMIs on this CPU. |
| * If we own the commit event, then we can commit |
| * all others that interrupted us, since the interruptions |
| * are in stack format (they finish before they come |
| * back to us). This allows us to do a simple loop to |
| * assign the commit to the tail. |
| */ |
| again: |
| max_count = cpu_buffer->nr_pages * 100; |
| |
| while (cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page)) { |
| if (RB_WARN_ON(cpu_buffer, !(--max_count))) |
| return; |
| if (RB_WARN_ON(cpu_buffer, |
| rb_is_reader_page(cpu_buffer->tail_page))) |
| return; |
| local_set(&cpu_buffer->commit_page->page->commit, |
| rb_page_write(cpu_buffer->commit_page)); |
| rb_inc_page(cpu_buffer, &cpu_buffer->commit_page); |
| /* Only update the write stamp if the page has an event */ |
| if (rb_page_write(cpu_buffer->commit_page)) |
| cpu_buffer->write_stamp = |
| cpu_buffer->commit_page->page->time_stamp; |
| /* add barrier to keep gcc from optimizing too much */ |
| barrier(); |
| } |
| while (rb_commit_index(cpu_buffer) != |
| rb_page_write(cpu_buffer->commit_page)) { |
| |
| local_set(&cpu_buffer->commit_page->page->commit, |
| rb_page_write(cpu_buffer->commit_page)); |
| RB_WARN_ON(cpu_buffer, |
| local_read(&cpu_buffer->commit_page->page->commit) & |
| ~RB_WRITE_MASK); |
| barrier(); |
| } |
| |
| /* again, keep gcc from optimizing */ |
| barrier(); |
| |
| /* |
| * If an interrupt came in just after the first while loop |
| * and pushed the tail page forward, we will be left with |
| * a dangling commit that will never go forward. |
| */ |
| if (unlikely(cpu_buffer->commit_page != READ_ONCE(cpu_buffer->tail_page))) |
| goto again; |
| } |
| |
| static __always_inline void rb_end_commit(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| unsigned long commits; |
| |
| if (RB_WARN_ON(cpu_buffer, |
| !local_read(&cpu_buffer->committing))) |
| return; |
| |
| again: |
| commits = local_read(&cpu_buffer->commits); |
| /* synchronize with interrupts */ |
| barrier(); |
| if (local_read(&cpu_buffer->committing) == 1) |
| rb_set_commit_to_write(cpu_buffer); |
| |
| local_dec(&cpu_buffer->committing); |
| |
| /* synchronize with interrupts */ |
| barrier(); |
| |
| /* |
| * Need to account for interrupts coming in between the |
| * updating of the commit page and the clearing of the |
| * committing counter. |
| */ |
| if (unlikely(local_read(&cpu_buffer->commits) != commits) && |
| !local_read(&cpu_buffer->committing)) { |
| local_inc(&cpu_buffer->committing); |
| goto again; |
| } |
| } |
| |
| static inline void rb_event_discard(struct ring_buffer_event *event) |
| { |
| if (extended_time(event)) |
| event = skip_time_extend(event); |
| |
| /* array[0] holds the actual length for the discarded event */ |
| event->array[0] = rb_event_data_length(event) - RB_EVNT_HDR_SIZE; |
| event->type_len = RINGBUF_TYPE_PADDING; |
| /* time delta must be non zero */ |
| if (!event->time_delta) |
| event->time_delta = 1; |
| } |
| |
| static __always_inline bool |
| rb_event_is_commit(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event) |
| { |
| unsigned long addr = (unsigned long)event; |
| unsigned long index; |
| |
| index = rb_event_index(event); |
| addr &= PAGE_MASK; |
| |
| return cpu_buffer->commit_page->page == (void *)addr && |
| rb_commit_index(cpu_buffer) == index; |
| } |
| |
| static __always_inline void |
| rb_update_write_stamp(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event) |
| { |
| u64 delta; |
| |
| /* |
| * The event first in the commit queue updates the |
| * time stamp. |
| */ |
| if (rb_event_is_commit(cpu_buffer, event)) { |
| /* |
| * A commit event that is first on a page |
| * updates the write timestamp with the page stamp |
| */ |
| if (!rb_event_index(event)) |
| cpu_buffer->write_stamp = |
| cpu_buffer->commit_page->page->time_stamp; |
| else if (event->type_len == RINGBUF_TYPE_TIME_EXTEND) { |
| delta = ring_buffer_event_time_stamp(event); |
| cpu_buffer->write_stamp += delta; |
| } else if (event->type_len == RINGBUF_TYPE_TIME_STAMP) { |
| delta = ring_buffer_event_time_stamp(event); |
| cpu_buffer->write_stamp = delta; |
| } else |
| cpu_buffer->write_stamp += event->time_delta; |
| } |
| } |
| |
| static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event) |
| { |
| local_inc(&cpu_buffer->entries); |
| rb_update_write_stamp(cpu_buffer, event); |
| rb_end_commit(cpu_buffer); |
| } |
| |
| static __always_inline void |
| rb_wakeups(struct ring_buffer *buffer, struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| size_t nr_pages; |
| size_t dirty; |
| size_t full; |
| |
| if (buffer->irq_work.waiters_pending) { |
| buffer->irq_work.waiters_pending = false; |
| /* irq_work_queue() supplies it's own memory barriers */ |
| irq_work_queue(&buffer->irq_work.work); |
| } |
| |
| if (cpu_buffer->irq_work.waiters_pending) { |
| cpu_buffer->irq_work.waiters_pending = false; |
| /* irq_work_queue() supplies it's own memory barriers */ |
| irq_work_queue(&cpu_buffer->irq_work.work); |
| } |
| |
| if (cpu_buffer->last_pages_touch == local_read(&cpu_buffer->pages_touched)) |
| return; |
| |
| if (cpu_buffer->reader_page == cpu_buffer->commit_page) |
| return; |
| |
| if (!cpu_buffer->irq_work.full_waiters_pending) |
| return; |
| |
| cpu_buffer->last_pages_touch = local_read(&cpu_buffer->pages_touched); |
| |
| full = cpu_buffer->shortest_full; |
| nr_pages = cpu_buffer->nr_pages; |
| dirty = ring_buffer_nr_dirty_pages(buffer, cpu_buffer->cpu); |
| if (full && nr_pages && (dirty * 100) <= full * nr_pages) |
| return; |
| |
| cpu_buffer->irq_work.wakeup_full = true; |
| cpu_buffer->irq_work.full_waiters_pending = false; |
| /* irq_work_queue() supplies it's own memory barriers */ |
| irq_work_queue(&cpu_buffer->irq_work.work); |
| } |
| |
| /* |
| * The lock and unlock are done within a preempt disable section. |
| * The current_context per_cpu variable can only be modified |
| * by the current task between lock and unlock. But it can |
| * be modified more than once via an interrupt. To pass this |
| * information from the lock to the unlock without having to |
| * access the 'in_interrupt()' functions again (which do show |
| * a bit of overhead in something as critical as function tracing, |
| * we use a bitmask trick. |
| * |
| * bit 0 = NMI context |
| * bit 1 = IRQ context |
| * bit 2 = SoftIRQ context |
| * bit 3 = normal context. |
| * |
| * This works because this is the order of contexts that can |
| * preempt other contexts. A SoftIRQ never preempts an IRQ |
| * context. |
| * |
| * When the context is determined, the corresponding bit is |
| * checked and set (if it was set, then a recursion of that context |
| * happened). |
| * |
| * On unlock, we need to clear this bit. To do so, just subtract |
| * 1 from the current_context and AND it to itself. |
| * |
| * (binary) |
| * 101 - 1 = 100 |
| * 101 & 100 = 100 (clearing bit zero) |
| * |
| * 1010 - 1 = 1001 |
| * 1010 & 1001 = 1000 (clearing bit 1) |
| * |
| * The least significant bit can be cleared this way, and it |
| * just so happens that it is the same bit corresponding to |
| * the current context. |
| */ |
| |
| static __always_inline int |
| trace_recursive_lock(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| unsigned int val = cpu_buffer->current_context; |
| unsigned long pc = preempt_count(); |
| int bit; |
| |
| if (!(pc & (NMI_MASK | HARDIRQ_MASK | SOFTIRQ_OFFSET))) |
| bit = RB_CTX_NORMAL; |
| else |
| bit = pc & NMI_MASK ? RB_CTX_NMI : |
| pc & HARDIRQ_MASK ? RB_CTX_IRQ : RB_CTX_SOFTIRQ; |
| |
| if (unlikely(val & (1 << (bit + cpu_buffer->nest)))) |
| return 1; |
| |
| val |= (1 << (bit + cpu_buffer->nest)); |
| cpu_buffer->current_context = val; |
| |
| return 0; |
| } |
| |
| static __always_inline void |
| trace_recursive_unlock(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| cpu_buffer->current_context &= |
| cpu_buffer->current_context - (1 << cpu_buffer->nest); |
| } |
| |
| /* The recursive locking above uses 4 bits */ |
| #define NESTED_BITS 4 |
| |
| /** |
| * ring_buffer_nest_start - Allow to trace while nested |
| * @buffer: The ring buffer to modify |
| * |
| * The ring buffer has a safety mechanism to prevent recursion. |
| * But there may be a case where a trace needs to be done while |
| * tracing something else. In this case, calling this function |
| * will allow this function to nest within a currently active |
| * ring_buffer_lock_reserve(). |
| * |
| * Call this function before calling another ring_buffer_lock_reserve() and |
| * call ring_buffer_nest_end() after the nested ring_buffer_unlock_commit(). |
| */ |
| void ring_buffer_nest_start(struct ring_buffer *buffer) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| int cpu; |
| |
| /* Enabled by ring_buffer_nest_end() */ |
| preempt_disable_notrace(); |
| cpu = raw_smp_processor_id(); |
| cpu_buffer = buffer->buffers[cpu]; |
| /* This is the shift value for the above recursive locking */ |
| cpu_buffer->nest += NESTED_BITS; |
| } |
| |
| /** |
| * ring_buffer_nest_end - Allow to trace while nested |
| * @buffer: The ring buffer to modify |
| * |
| * Must be called after ring_buffer_nest_start() and after the |
| * ring_buffer_unlock_commit(). |
| */ |
| void ring_buffer_nest_end(struct ring_buffer *buffer) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| int cpu; |
| |
| /* disabled by ring_buffer_nest_start() */ |
| cpu = raw_smp_processor_id(); |
| cpu_buffer = buffer->buffers[cpu]; |
| /* This is the shift value for the above recursive locking */ |
| cpu_buffer->nest -= NESTED_BITS; |
| preempt_enable_notrace(); |
| } |
| |
| /** |
| * ring_buffer_unlock_commit - commit a reserved |
| * @buffer: The buffer to commit to |
| * @event: The event pointer to commit. |
| * |
| * This commits the data to the ring buffer, and releases any locks held. |
| * |
| * Must be paired with ring_buffer_lock_reserve. |
| */ |
| int ring_buffer_unlock_commit(struct ring_buffer *buffer, |
| struct ring_buffer_event *event) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| int cpu = raw_smp_processor_id(); |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| rb_commit(cpu_buffer, event); |
| |
| rb_wakeups(buffer, cpu_buffer); |
| |
| trace_recursive_unlock(cpu_buffer); |
| |
| preempt_enable_notrace(); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit); |
| |
| static noinline void |
| rb_handle_timestamp(struct ring_buffer_per_cpu *cpu_buffer, |
| struct rb_event_info *info) |
| { |
| WARN_ONCE(info->delta > (1ULL << 59), |
| KERN_WARNING "Delta way too big! %llu ts=%llu write stamp = %llu\n%s", |
| (unsigned long long)info->delta, |
| (unsigned long long)info->ts, |
| (unsigned long long)cpu_buffer->write_stamp, |
| sched_clock_stable() ? "" : |
| "If you just came from a suspend/resume,\n" |
| "please switch to the trace global clock:\n" |
| " echo global > /sys/kernel/debug/tracing/trace_clock\n" |
| "or add trace_clock=global to the kernel command line\n"); |
| info->add_timestamp = 1; |
| } |
| |
| static struct ring_buffer_event * |
| __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, |
| struct rb_event_info *info) |
| { |
| struct ring_buffer_event *event; |
| struct buffer_page *tail_page; |
| unsigned long tail, write; |
| |
| /* |
| * If the time delta since the last event is too big to |
| * hold in the time field of the event, then we append a |
| * TIME EXTEND event ahead of the data event. |
| */ |
| if (unlikely(info->add_timestamp)) |
| info->length += RB_LEN_TIME_EXTEND; |
| |
| /* Don't let the compiler play games with cpu_buffer->tail_page */ |
| tail_page = info->tail_page = READ_ONCE(cpu_buffer->tail_page); |
| write = local_add_return(info->length, &tail_page->write); |
| |
| /* set write to only the index of the write */ |
| write &= RB_WRITE_MASK; |
| tail = write - info->length; |
| |
| /* |
| * If this is the first commit on the page, then it has the same |
| * timestamp as the page itself. |
| */ |
| if (!tail && !ring_buffer_time_stamp_abs(cpu_buffer->buffer)) |
| info->delta = 0; |
| |
| /* See if we shot pass the end of this buffer page */ |
| if (unlikely(write > BUF_PAGE_SIZE)) |
| return rb_move_tail(cpu_buffer, tail, info); |
| |
| /* We reserved something on the buffer */ |
| |
| event = __rb_page_index(tail_page, tail); |
| rb_update_event(cpu_buffer, event, info); |
| |
| local_inc(&tail_page->entries); |
| |
| /* |
| * If this is the first commit on the page, then update |
| * its timestamp. |
| */ |
| if (!tail) |
| tail_page->page->time_stamp = info->ts; |
| |
| /* account for these added bytes */ |
| local_add(info->length, &cpu_buffer->entries_bytes); |
| |
| return event; |
| } |
| |
| static __always_inline struct ring_buffer_event * |
| rb_reserve_next_event(struct ring_buffer *buffer, |
| struct ring_buffer_per_cpu *cpu_buffer, |
| unsigned long length) |
| { |
| struct ring_buffer_event *event; |
| struct rb_event_info info; |
| int nr_loops = 0; |
| u64 diff; |
| |
| rb_start_commit(cpu_buffer); |
| |
| #ifdef CONFIG_RING_BUFFER_ALLOW_SWAP |
| /* |
| * Due to the ability to swap a cpu buffer from a buffer |
| * it is possible it was swapped before we committed. |
| * (committing stops a swap). We check for it here and |
| * if it happened, we have to fail the write. |
| */ |
| barrier(); |
| if (unlikely(READ_ONCE(cpu_buffer->buffer) != buffer)) { |
| local_dec(&cpu_buffer->committing); |
| local_dec(&cpu_buffer->commits); |
| return NULL; |
| } |
| #endif |
| |
| info.length = rb_calculate_event_length(length); |
| again: |
| info.add_timestamp = 0; |
| info.delta = 0; |
| |
| /* |
| * We allow for interrupts to reenter here and do a trace. |
| * If one does, it will cause this original code to loop |
| * back here. Even with heavy interrupts happening, this |
| * should only happen a few times in a row. If this happens |
| * 1000 times in a row, there must be either an interrupt |
| * storm or we have something buggy. |
| * Bail! |
| */ |
| if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000)) |
| goto out_fail; |
| |
| info.ts = rb_time_stamp(cpu_buffer->buffer); |
| diff = info.ts - cpu_buffer->write_stamp; |
| |
| /* make sure this diff is calculated here */ |
| barrier(); |
| |
| if (ring_buffer_time_stamp_abs(buffer)) { |
| info.delta = info.ts; |
| rb_handle_timestamp(cpu_buffer, &info); |
| } else /* Did the write stamp get updated already? */ |
| if (likely(info.ts >= cpu_buffer->write_stamp)) { |
| info.delta = diff; |
| if (unlikely(test_time_stamp(info.delta))) |
| rb_handle_timestamp(cpu_buffer, &info); |
| } |
| |
| event = __rb_reserve_next(cpu_buffer, &info); |
| |
| if (unlikely(PTR_ERR(event) == -EAGAIN)) { |
| if (info.add_timestamp) |
| info.length -= RB_LEN_TIME_EXTEND; |
| goto again; |
| } |
| |
| if (!event) |
| goto out_fail; |
| |
| return event; |
| |
| out_fail: |
| rb_end_commit(cpu_buffer); |
| return NULL; |
| } |
| |
| /** |
| * ring_buffer_lock_reserve - reserve a part of the buffer |
| * @buffer: the ring buffer to reserve from |
| * @length: the length of the data to reserve (excluding event header) |
| * |
| * Returns a reserved event on the ring buffer to copy directly to. |
| * The user of this interface will need to get the body to write into |
| * and can use the ring_buffer_event_data() interface. |
| * |
| * The length is the length of the data needed, not the event length |
| * which also includes the event header. |
| * |
| * Must be paired with ring_buffer_unlock_commit, unless NULL is returned. |
| * If NULL is returned, then nothing has been allocated or locked. |
| */ |
| struct ring_buffer_event * |
| ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| struct ring_buffer_event *event; |
| int cpu; |
| |
| /* If we are tracing schedule, we don't want to recurse */ |
| preempt_disable_notrace(); |
| |
| if (unlikely(atomic_read(&buffer->record_disabled))) |
| goto out; |
| |
| cpu = raw_smp_processor_id(); |
| |
| if (unlikely(!cpumask_test_cpu(cpu, buffer->cpumask))) |
| goto out; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| if (unlikely(atomic_read(&cpu_buffer->record_disabled))) |
| goto out; |
| |
| if (unlikely(length > BUF_MAX_DATA_SIZE)) |
| goto out; |
| |
| if (unlikely(trace_recursive_lock(cpu_buffer))) |
| goto out; |
| |
| event = rb_reserve_next_event(buffer, cpu_buffer, length); |
| if (!event) |
| goto out_unlock; |
| |
| return event; |
| |
| out_unlock: |
| trace_recursive_unlock(cpu_buffer); |
| out: |
| preempt_enable_notrace(); |
| return NULL; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve); |
| |
| /* |
| * Decrement the entries to the page that an event is on. |
| * The event does not even need to exist, only the pointer |
| * to the page it is on. This may only be called before the commit |
| * takes place. |
| */ |
| static inline void |
| rb_decrement_entry(struct ring_buffer_per_cpu *cpu_buffer, |
| struct ring_buffer_event *event) |
| { |
| unsigned long addr = (unsigned long)event; |
| struct buffer_page *bpage = cpu_buffer->commit_page; |
| struct buffer_page *start; |
| |
| addr &= PAGE_MASK; |
| |
| /* Do the likely case first */ |
| if (likely(bpage->page == (void *)addr)) { |
| local_dec(&bpage->entries); |
| return; |
| } |
| |
| /* |
| * Because the commit page may be on the reader page we |
| * start with the next page and check the end loop there. |
| */ |
| rb_inc_page(cpu_buffer, &bpage); |
| start = bpage; |
| do { |
| if (bpage->page == (void *)addr) { |
| local_dec(&bpage->entries); |
| return; |
| } |
| rb_inc_page(cpu_buffer, &bpage); |
| } while (bpage != start); |
| |
| /* commit not part of this buffer?? */ |
| RB_WARN_ON(cpu_buffer, 1); |
| } |
| |
| /** |
| * ring_buffer_commit_discard - discard an event that has not been committed |
| * @buffer: the ring buffer |
| * @event: non committed event to discard |
| * |
| * Sometimes an event that is in the ring buffer needs to be ignored. |
| * This function lets the user discard an event in the ring buffer |
| * and then that event will not be read later. |
| * |
| * This function only works if it is called before the item has been |
| * committed. It will try to free the event from the ring buffer |
| * if another event has not been added behind it. |
| * |
| * If another event has been added behind it, it will set the event |
| * up as discarded, and perform the commit. |
| * |
| * If this function is called, do not call ring_buffer_unlock_commit on |
| * the event. |
| */ |
| void ring_buffer_discard_commit(struct ring_buffer *buffer, |
| struct ring_buffer_event *event) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| int cpu; |
| |
| /* The event is discarded regardless */ |
| rb_event_discard(event); |
| |
| cpu = smp_processor_id(); |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| /* |
| * This must only be called if the event has not been |
| * committed yet. Thus we can assume that preemption |
| * is still disabled. |
| */ |
| RB_WARN_ON(buffer, !local_read(&cpu_buffer->committing)); |
| |
| rb_decrement_entry(cpu_buffer, event); |
| if (rb_try_to_discard(cpu_buffer, event)) |
| goto out; |
| |
| /* |
| * The commit is still visible by the reader, so we |
| * must still update the timestamp. |
| */ |
| rb_update_write_stamp(cpu_buffer, event); |
| out: |
| rb_end_commit(cpu_buffer); |
| |
| trace_recursive_unlock(cpu_buffer); |
| |
| preempt_enable_notrace(); |
| |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_discard_commit); |
| |
| /** |
| * ring_buffer_write - write data to the buffer without reserving |
| * @buffer: The ring buffer to write to. |
| * @length: The length of the data being written (excluding the event header) |
| * @data: The data to write to the buffer. |
| * |
| * This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as |
| * one function. If you already have the data to write to the buffer, it |
| * may be easier to simply call this function. |
| * |
| * Note, like ring_buffer_lock_reserve, the length is the length of the data |
| * and not the length of the event which would hold the header. |
| */ |
| int ring_buffer_write(struct ring_buffer *buffer, |
| unsigned long length, |
| void *data) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| struct ring_buffer_event *event; |
| void *body; |
| int ret = -EBUSY; |
| int cpu; |
| |
| preempt_disable_notrace(); |
| |
| if (atomic_read(&buffer->record_disabled)) |
| goto out; |
| |
| cpu = raw_smp_processor_id(); |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| goto out; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| if (atomic_read(&cpu_buffer->record_disabled)) |
| goto out; |
| |
| if (length > BUF_MAX_DATA_SIZE) |
| goto out; |
| |
| if (unlikely(trace_recursive_lock(cpu_buffer))) |
| goto out; |
| |
| event = rb_reserve_next_event(buffer, cpu_buffer, length); |
| if (!event) |
| goto out_unlock; |
| |
| body = rb_event_data(event); |
| |
| memcpy(body, data, length); |
| |
| rb_commit(cpu_buffer, event); |
| |
| rb_wakeups(buffer, cpu_buffer); |
| |
| ret = 0; |
| |
| out_unlock: |
| trace_recursive_unlock(cpu_buffer); |
| |
| out: |
| preempt_enable_notrace(); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_write); |
| |
| static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| struct buffer_page *reader = cpu_buffer->reader_page; |
| struct buffer_page *head = rb_set_head_page(cpu_buffer); |
| struct buffer_page *commit = cpu_buffer->commit_page; |
| |
| /* In case of error, head will be NULL */ |
| if (unlikely(!head)) |
| return true; |
| |
| return reader->read == rb_page_commit(reader) && |
| (commit == reader || |
| (commit == head && |
| head->read == rb_page_commit(commit))); |
| } |
| |
| /** |
| * ring_buffer_record_disable - stop all writes into the buffer |
| * @buffer: The ring buffer to stop writes to. |
| * |
| * This prevents all writes to the buffer. Any attempt to write |
| * to the buffer after this will fail and return NULL. |
| * |
| * The caller should call synchronize_rcu() after this. |
| */ |
| void ring_buffer_record_disable(struct ring_buffer *buffer) |
| { |
| atomic_inc(&buffer->record_disabled); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_disable); |
| |
| /** |
| * ring_buffer_record_enable - enable writes to the buffer |
| * @buffer: The ring buffer to enable writes |
| * |
| * Note, multiple disables will need the same number of enables |
| * to truly enable the writing (much like preempt_disable). |
| */ |
| void ring_buffer_record_enable(struct ring_buffer *buffer) |
| { |
| atomic_dec(&buffer->record_disabled); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_enable); |
| |
| /** |
| * ring_buffer_record_off - stop all writes into the buffer |
| * @buffer: The ring buffer to stop writes to. |
| * |
| * This prevents all writes to the buffer. Any attempt to write |
| * to the buffer after this will fail and return NULL. |
| * |
| * This is different than ring_buffer_record_disable() as |
| * it works like an on/off switch, where as the disable() version |
| * must be paired with a enable(). |
| */ |
| void ring_buffer_record_off(struct ring_buffer *buffer) |
| { |
| unsigned int rd; |
| unsigned int new_rd; |
| |
| do { |
| rd = atomic_read(&buffer->record_disabled); |
| new_rd = rd | RB_BUFFER_OFF; |
| } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_off); |
| |
| /** |
| * ring_buffer_record_on - restart writes into the buffer |
| * @buffer: The ring buffer to start writes to. |
| * |
| * This enables all writes to the buffer that was disabled by |
| * ring_buffer_record_off(). |
| * |
| * This is different than ring_buffer_record_enable() as |
| * it works like an on/off switch, where as the enable() version |
| * must be paired with a disable(). |
| */ |
| void ring_buffer_record_on(struct ring_buffer *buffer) |
| { |
| unsigned int rd; |
| unsigned int new_rd; |
| |
| do { |
| rd = atomic_read(&buffer->record_disabled); |
| new_rd = rd & ~RB_BUFFER_OFF; |
| } while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_on); |
| |
| /** |
| * ring_buffer_record_is_on - return true if the ring buffer can write |
| * @buffer: The ring buffer to see if write is enabled |
| * |
| * Returns true if the ring buffer is in a state that it accepts writes. |
| */ |
| bool ring_buffer_record_is_on(struct ring_buffer *buffer) |
| { |
| return !atomic_read(&buffer->record_disabled); |
| } |
| |
| /** |
| * ring_buffer_record_is_set_on - return true if the ring buffer is set writable |
| * @buffer: The ring buffer to see if write is set enabled |
| * |
| * Returns true if the ring buffer is set writable by ring_buffer_record_on(). |
| * Note that this does NOT mean it is in a writable state. |
| * |
| * It may return true when the ring buffer has been disabled by |
| * ring_buffer_record_disable(), as that is a temporary disabling of |
| * the ring buffer. |
| */ |
| bool ring_buffer_record_is_set_on(struct ring_buffer *buffer) |
| { |
| return !(atomic_read(&buffer->record_disabled) & RB_BUFFER_OFF); |
| } |
| |
| /** |
| * ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer |
| * @buffer: The ring buffer to stop writes to. |
| * @cpu: The CPU buffer to stop |
| * |
| * This prevents all writes to the buffer. Any attempt to write |
| * to the buffer after this will fail and return NULL. |
| * |
| * The caller should call synchronize_rcu() after this. |
| */ |
| void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| atomic_inc(&cpu_buffer->record_disabled); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu); |
| |
| /** |
| * ring_buffer_record_enable_cpu - enable writes to the buffer |
| * @buffer: The ring buffer to enable writes |
| * @cpu: The CPU to enable. |
| * |
| * Note, multiple disables will need the same number of enables |
| * to truly enable the writing (much like preempt_disable). |
| */ |
| void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| atomic_dec(&cpu_buffer->record_disabled); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu); |
| |
| /* |
| * The total entries in the ring buffer is the running counter |
| * of entries entered into the ring buffer, minus the sum of |
| * the entries read from the ring buffer and the number of |
| * entries that were overwritten. |
| */ |
| static inline unsigned long |
| rb_num_of_entries(struct ring_buffer_per_cpu *cpu_buffer) |
| { |
| return local_read(&cpu_buffer->entries) - |
| (local_read(&cpu_buffer->overrun) + cpu_buffer->read); |
| } |
| |
| /** |
| * ring_buffer_oldest_event_ts - get the oldest event timestamp from the buffer |
| * @buffer: The ring buffer |
| * @cpu: The per CPU buffer to read from. |
| */ |
| u64 ring_buffer_oldest_event_ts(struct ring_buffer *buffer, int cpu) |
| { |
| unsigned long flags; |
| struct ring_buffer_per_cpu *cpu_buffer; |
| struct buffer_page *bpage; |
| u64 ret = 0; |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return 0; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| raw_spin_lock_irqsave(&cpu_buffer->reader_lock, flags); |
| /* |
| * if the tail is on reader_page, oldest time stamp is on the reader |
| * page |
| */ |
| if (cpu_buffer->tail_page == cpu_buffer->reader_page) |
| bpage = cpu_buffer->reader_page; |
| else |
| bpage = rb_set_head_page(cpu_buffer); |
| if (bpage) |
| ret = bpage->page->time_stamp; |
| raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_oldest_event_ts); |
| |
| /** |
| * ring_buffer_bytes_cpu - get the number of bytes consumed in a cpu buffer |
| * @buffer: The ring buffer |
| * @cpu: The per CPU buffer to read from. |
| */ |
| unsigned long ring_buffer_bytes_cpu(struct ring_buffer *buffer, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| unsigned long ret; |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return 0; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| ret = local_read(&cpu_buffer->entries_bytes) - cpu_buffer->read_bytes; |
| |
| return ret; |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_bytes_cpu); |
| |
| /** |
| * ring_buffer_entries_cpu - get the number of entries in a cpu buffer |
| * @buffer: The ring buffer |
| * @cpu: The per CPU buffer to get the entries from. |
| */ |
| unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer; |
| |
| if (!cpumask_test_cpu(cpu, buffer->cpumask)) |
| return 0; |
| |
| cpu_buffer = buffer->buffers[cpu]; |
| |
| return rb_num_of_entries(cpu_buffer); |
| } |
| EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu); |
| |
| /** |
| * ring_buffer_overrun_cpu - get the number of overruns caused by the ring |
| * buffer wrapping around (only if RB_FL_OVERWRITE is on). |
| * @buffer: The ring buffer |
| * @cpu: The per CPU buffer to get the number of overruns from |
| */ |
| unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu) |
| { |
| struct ring_buffer_per_cpu *cpu_buffer |