sched/wait: Split out the wait_bit*() APIs from <linux/wait.h> into <linux/wait_bit.h>
The wait_bit*() types and APIs are mixed into wait.h, but they
are a pretty orthogonal extension of wait-queues.
Furthermore, only about 50 kernel files use these APIs, while
over 1000 use the regular wait-queue functionality.
So clean up the main wait.h by moving the wait-bit functionality
out of it, into a separate .h and .c file:
include/linux/wait_bit.h for types and APIs
kernel/sched/wait_bit.c for the implementation
Update all header dependencies.
This reduces the size of wait.h rather significantly, by about 30%.
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/sched/wait_bit.c b/kernel/sched/wait_bit.c
new file mode 100644
index 0000000..463bac8
--- /dev/null
+++ b/kernel/sched/wait_bit.c
@@ -0,0 +1,263 @@
+/*
+ * The implementation of the wait_bit*() and related waiting APIs:
+ */
+#include <linux/wait_bit.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/debug.h>
+
+int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
+{
+ struct wait_bit_key *key = arg;
+ struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
+
+ if (wait_bit->key.flags != key->flags ||
+ wait_bit->key.bit_nr != key->bit_nr ||
+ test_bit(key->bit_nr, key->flags))
+ return 0;
+ else
+ return autoremove_wake_function(wq_entry, mode, sync, key);
+}
+EXPORT_SYMBOL(wake_bit_function);
+
+/*
+ * To allow interruptible waiting and asynchronous (i.e. nonblocking)
+ * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
+ * permitted return codes. Nonzero return codes halt waiting and return.
+ */
+int __sched
+__wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
+ wait_bit_action_f *action, unsigned mode)
+{
+ int ret = 0;
+
+ do {
+ prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
+ if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags))
+ ret = (*action)(&wbq_entry->key, mode);
+ } while (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
+ finish_wait(wq_head, &wbq_entry->wq_entry);
+ return ret;
+}
+EXPORT_SYMBOL(__wait_on_bit);
+
+int __sched out_of_line_wait_on_bit(void *word, int bit,
+ wait_bit_action_f *action, unsigned mode)
+{
+ struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
+ DEFINE_WAIT_BIT(wq_entry, word, bit);
+
+ return __wait_on_bit(wq_head, &wq_entry, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit);
+
+int __sched out_of_line_wait_on_bit_timeout(
+ void *word, int bit, wait_bit_action_f *action,
+ unsigned mode, unsigned long timeout)
+{
+ struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
+ DEFINE_WAIT_BIT(wq_entry, word, bit);
+
+ wq_entry.key.timeout = jiffies + timeout;
+ return __wait_on_bit(wq_head, &wq_entry, action, mode);
+}
+EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
+
+int __sched
+__wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
+ wait_bit_action_f *action, unsigned mode)
+{
+ int ret = 0;
+
+ for (;;) {
+ prepare_to_wait_exclusive(wq_head, &wbq_entry->wq_entry, mode);
+ if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
+ ret = action(&wbq_entry->key, mode);
+ /*
+ * See the comment in prepare_to_wait_event().
+ * finish_wait() does not necessarily takes wwq_head->lock,
+ * but test_and_set_bit() implies mb() which pairs with
+ * smp_mb__after_atomic() before wake_up_page().
+ */
+ if (ret)
+ finish_wait(wq_head, &wbq_entry->wq_entry);
+ }
+ if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
+ if (!ret)
+ finish_wait(wq_head, &wbq_entry->wq_entry);
+ return 0;
+ } else if (ret) {
+ return ret;
+ }
+ }
+}
+EXPORT_SYMBOL(__wait_on_bit_lock);
+
+int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
+ wait_bit_action_f *action, unsigned mode)
+{
+ struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
+ DEFINE_WAIT_BIT(wq_entry, word, bit);
+
+ return __wait_on_bit_lock(wq_head, &wq_entry, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
+
+void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit)
+{
+ struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
+ if (waitqueue_active(wq_head))
+ __wake_up(wq_head, TASK_NORMAL, 1, &key);
+}
+EXPORT_SYMBOL(__wake_up_bit);
+
+/**
+ * wake_up_bit - wake up a waiter on a bit
+ * @word: the word being waited on, a kernel virtual address
+ * @bit: the bit of the word being waited on
+ *
+ * There is a standard hashed waitqueue table for generic use. This
+ * is the part of the hashtable's accessor API that wakes up waiters
+ * on a bit. For instance, if one were to have waiters on a bitflag,
+ * one would call wake_up_bit() after clearing the bit.
+ *
+ * In order for this to function properly, as it uses waitqueue_active()
+ * internally, some kind of memory barrier must be done prior to calling
+ * this. Typically, this will be smp_mb__after_atomic(), but in some
+ * cases where bitflags are manipulated non-atomically under a lock, one
+ * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
+ * because spin_unlock() does not guarantee a memory barrier.
+ */
+void wake_up_bit(void *word, int bit)
+{
+ __wake_up_bit(bit_waitqueue(word, bit), word, bit);
+}
+EXPORT_SYMBOL(wake_up_bit);
+
+/*
+ * Manipulate the atomic_t address to produce a better bit waitqueue table hash
+ * index (we're keying off bit -1, but that would produce a horrible hash
+ * value).
+ */
+static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
+{
+ if (BITS_PER_LONG == 64) {
+ unsigned long q = (unsigned long)p;
+ return bit_waitqueue((void *)(q & ~1), q & 1);
+ }
+ return bit_waitqueue(p, 0);
+}
+
+static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync,
+ void *arg)
+{
+ struct wait_bit_key *key = arg;
+ struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
+ atomic_t *val = key->flags;
+
+ if (wait_bit->key.flags != key->flags ||
+ wait_bit->key.bit_nr != key->bit_nr ||
+ atomic_read(val) != 0)
+ return 0;
+ return autoremove_wake_function(wq_entry, mode, sync, key);
+}
+
+/*
+ * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting,
+ * the actions of __wait_on_atomic_t() are permitted return codes. Nonzero
+ * return codes halt waiting and return.
+ */
+static __sched
+int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
+ int (*action)(atomic_t *), unsigned mode)
+{
+ atomic_t *val;
+ int ret = 0;
+
+ do {
+ prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
+ val = wbq_entry->key.flags;
+ if (atomic_read(val) == 0)
+ break;
+ ret = (*action)(val);
+ } while (!ret && atomic_read(val) != 0);
+ finish_wait(wq_head, &wbq_entry->wq_entry);
+ return ret;
+}
+
+#define DEFINE_WAIT_ATOMIC_T(name, p) \
+ struct wait_bit_queue_entry name = { \
+ .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p), \
+ .wq_entry = { \
+ .private = current, \
+ .func = wake_atomic_t_function, \
+ .task_list = \
+ LIST_HEAD_INIT((name).wq_entry.task_list), \
+ }, \
+ }
+
+__sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),
+ unsigned mode)
+{
+ struct wait_queue_head *wq_head = atomic_t_waitqueue(p);
+ DEFINE_WAIT_ATOMIC_T(wq_entry, p);
+
+ return __wait_on_atomic_t(wq_head, &wq_entry, action, mode);
+}
+EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
+
+/**
+ * wake_up_atomic_t - Wake up a waiter on a atomic_t
+ * @p: The atomic_t being waited on, a kernel virtual address
+ *
+ * Wake up anyone waiting for the atomic_t to go to zero.
+ *
+ * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t
+ * check is done by the waiter's wake function, not the by the waker itself).
+ */
+void wake_up_atomic_t(atomic_t *p)
+{
+ __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
+}
+EXPORT_SYMBOL(wake_up_atomic_t);
+
+__sched int bit_wait(struct wait_bit_key *word, int mode)
+{
+ schedule();
+ if (signal_pending_state(mode, current))
+ return -EINTR;
+ return 0;
+}
+EXPORT_SYMBOL(bit_wait);
+
+__sched int bit_wait_io(struct wait_bit_key *word, int mode)
+{
+ io_schedule();
+ if (signal_pending_state(mode, current))
+ return -EINTR;
+ return 0;
+}
+EXPORT_SYMBOL(bit_wait_io);
+
+__sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
+{
+ unsigned long now = READ_ONCE(jiffies);
+ if (time_after_eq(now, word->timeout))
+ return -EAGAIN;
+ schedule_timeout(word->timeout - now);
+ if (signal_pending_state(mode, current))
+ return -EINTR;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(bit_wait_timeout);
+
+__sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
+{
+ unsigned long now = READ_ONCE(jiffies);
+ if (time_after_eq(now, word->timeout))
+ return -EAGAIN;
+ io_schedule_timeout(word->timeout - now);
+ if (signal_pending_state(mode, current))
+ return -EINTR;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
