kernel/profile.c - linux - Git at Google

 /*
  *  linux/kernel/profile.c
  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
  *  with configurable resolution, support for restricting the cpus on
  *  which profiling is done, and switching between cpu time and
  *  schedule() calls via kernel command line parameters passed at boot.
  *
  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
  *	Red Hat, July 2004
  *  Consolidation of architecture support code for profiling,
  *	Nadia Yvette Chambers, Oracle, July 2004
  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  *	to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  *	Oracle, 2004
  */

 #include <linux/export.h>
 #include <linux/profile.h>
 #include <linux/memblock.h>
 #include <linux/notifier.h>
 #include <linux/mm.h>
 #include <linux/cpumask.h>
 #include <linux/cpu.h>
 #include <linux/highmem.h>
 #include <linux/mutex.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
 #include <linux/sched/stat.h>

 #include <asm/sections.h>
 #include <asm/irq_regs.h>
 #include <asm/ptrace.h>

 struct profile_hit {
 	u32 pc, hits;
 };
 #define PROFILE_GRPSHIFT	3
 #define PROFILE_GRPSZ		(1 << PROFILE_GRPSHIFT)
 #define NR_PROFILE_HIT		(PAGE_SIZE/sizeof(struct profile_hit))
 #define NR_PROFILE_GRP		(NR_PROFILE_HIT/PROFILE_GRPSZ)

 static atomic_t *prof_buffer;
 static unsigned long prof_len, prof_shift;

 int prof_on __read_mostly;
 EXPORT_SYMBOL_GPL(prof_on);

 static cpumask_var_t prof_cpu_mask;
 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
 static DEFINE_PER_CPU(int, cpu_profile_flip);
 static DEFINE_MUTEX(profile_flip_mutex);
 #endif /* CONFIG_SMP */

 int profile_setup(char *str)
 {
 	static const char schedstr[] = "schedule";
 	static const char sleepstr[] = "sleep";
 	static const char kvmstr[] = "kvm";
 	int par;

 	if (!strncmp(str, sleepstr, strlen(sleepstr))) {
 #ifdef CONFIG_SCHEDSTATS
 		force_schedstat_enabled();
 		prof_on = SLEEP_PROFILING;
 		if (str[strlen(sleepstr)] == ',')
 			str += strlen(sleepstr) + 1;
 		if (get_option(&str, &par))
 			prof_shift = par;
 		pr_info("kernel sleep profiling enabled (shift: %ld)\n",
 			prof_shift);
 #else
 		pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
 #endif /* CONFIG_SCHEDSTATS */
 	} else if (!strncmp(str, schedstr, strlen(schedstr))) {
 		prof_on = SCHED_PROFILING;
 		if (str[strlen(schedstr)] == ',')
 			str += strlen(schedstr) + 1;
 		if (get_option(&str, &par))
 			prof_shift = par;
 		pr_info("kernel schedule profiling enabled (shift: %ld)\n",
 			prof_shift);
 	} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
 		prof_on = KVM_PROFILING;
 		if (str[strlen(kvmstr)] == ',')
 			str += strlen(kvmstr) + 1;
 		if (get_option(&str, &par))
 			prof_shift = par;
 		pr_info("kernel KVM profiling enabled (shift: %ld)\n",
 			prof_shift);
 	} else if (get_option(&str, &par)) {
 		prof_shift = par;
 		prof_on = CPU_PROFILING;
 		pr_info("kernel profiling enabled (shift: %ld)\n",
 			prof_shift);
 	}
 	return 1;
 }
 __setup("profile=", profile_setup);


 int __ref profile_init(void)
 {
 	int buffer_bytes;
 	if (!prof_on)
 		return 0;

 	/* only text is profiled */
 	prof_len = (_etext - _stext) >> prof_shift;
 	buffer_bytes = prof_len*sizeof(atomic_t);

 	if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 		return -ENOMEM;

 	cpumask_copy(prof_cpu_mask, cpu_possible_mask);

 	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 	if (prof_buffer)
 		return 0;

 	prof_buffer = alloc_pages_exact(buffer_bytes,
 					GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 	if (prof_buffer)
 		return 0;

 	prof_buffer = vzalloc(buffer_bytes);
 	if (prof_buffer)
 		return 0;

 	free_cpumask_var(prof_cpu_mask);
 	return -ENOMEM;
 }

 /* Profile event notifications */

 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);

 void profile_task_exit(struct task_struct *task)
 {
 	blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 }

 int profile_handoff_task(struct task_struct *task)
 {
 	int ret;
 	ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 	return (ret == NOTIFY_OK) ? 1 : 0;
 }

 void profile_munmap(unsigned long addr)
 {
 	blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 }

 int task_handoff_register(struct notifier_block *n)
 {
 	return atomic_notifier_chain_register(&task_free_notifier, n);
 }
 EXPORT_SYMBOL_GPL(task_handoff_register);

 int task_handoff_unregister(struct notifier_block *n)
 {
 	return atomic_notifier_chain_unregister(&task_free_notifier, n);
 }
 EXPORT_SYMBOL_GPL(task_handoff_unregister);

 int profile_event_register(enum profile_type type, struct notifier_block *n)
 {
 	int err = -EINVAL;

 	switch (type) {
 	case PROFILE_TASK_EXIT:
 		err = blocking_notifier_chain_register(
 				&task_exit_notifier, n);
 		break;
 	case PROFILE_MUNMAP:
 		err = blocking_notifier_chain_register(
 				&munmap_notifier, n);
 		break;
 	}

 	return err;
 }
 EXPORT_SYMBOL_GPL(profile_event_register);

 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 {
 	int err = -EINVAL;

 	switch (type) {
 	case PROFILE_TASK_EXIT:
 		err = blocking_notifier_chain_unregister(
 				&task_exit_notifier, n);
 		break;
 	case PROFILE_MUNMAP:
 		err = blocking_notifier_chain_unregister(
 				&munmap_notifier, n);
 		break;
 	}

 	return err;
 }
 EXPORT_SYMBOL_GPL(profile_event_unregister);

 #if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
 /*
  * Each cpu has a pair of open-addressed hashtables for pending
  * profile hits. read_profile() IPI's all cpus to request them
  * to flip buffers and flushes their contents to prof_buffer itself.
  * Flip requests are serialized by the profile_flip_mutex. The sole
  * use of having a second hashtable is for avoiding cacheline
  * contention that would otherwise happen during flushes of pending
  * profile hits required for the accuracy of reported profile hits
  * and so resurrect the interrupt livelock issue.
  *
  * The open-addressed hashtables are indexed by profile buffer slot
  * and hold the number of pending hits to that profile buffer slot on
  * a cpu in an entry. When the hashtable overflows, all pending hits
  * are accounted to their corresponding profile buffer slots with
  * atomic_add() and the hashtable emptied. As numerous pending hits
  * may be accounted to a profile buffer slot in a hashtable entry,
  * this amortizes a number of atomic profile buffer increments likely
  * to be far larger than the number of entries in the hashtable,
  * particularly given that the number of distinct profile buffer
  * positions to which hits are accounted during short intervals (e.g.
  * several seconds) is usually very small. Exclusion from buffer
  * flipping is provided by interrupt disablement (note that for
  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
  * process context).
  * The hash function is meant to be lightweight as opposed to strong,
  * and was vaguely inspired by ppc64 firmware-supported inverted
  * pagetable hash functions, but uses a full hashtable full of finite
  * collision chains, not just pairs of them.
  *
  * -- nyc
  */
 static void __profile_flip_buffers(void *unused)
 {
 	int cpu = smp_processor_id();

 	per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 }

 static void profile_flip_buffers(void)
 {
 	int i, j, cpu;

 	mutex_lock(&profile_flip_mutex);
 	j = per_cpu(cpu_profile_flip, get_cpu());
 	put_cpu();
 	on_each_cpu(__profile_flip_buffers, NULL, 1);
 	for_each_online_cpu(cpu) {
 		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 		for (i = 0; i < NR_PROFILE_HIT; ++i) {
 			if (!hits[i].hits) {
 				if (hits[i].pc)
 					hits[i].pc = 0;
 				continue;
 			}
 			atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 			hits[i].hits = hits[i].pc = 0;
 		}
 	}
 	mutex_unlock(&profile_flip_mutex);
 }

 static void profile_discard_flip_buffers(void)
 {
 	int i, cpu;

 	mutex_lock(&profile_flip_mutex);
 	i = per_cpu(cpu_profile_flip, get_cpu());
 	put_cpu();
 	on_each_cpu(__profile_flip_buffers, NULL, 1);
 	for_each_online_cpu(cpu) {
 		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 		memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 	}
 	mutex_unlock(&profile_flip_mutex);
 }

 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 {
 	unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 	int i, j, cpu;
 	struct profile_hit *hits;

 	pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 	i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 	secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 	cpu = get_cpu();
 	hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 	if (!hits) {
 		put_cpu();
 		return;
 	}
 	/*
 	 * We buffer the global profiler buffer into a per-CPU
 	 * queue and thus reduce the number of global (and possibly
 	 * NUMA-alien) accesses. The write-queue is self-coalescing:
 	 */
 	local_irq_save(flags);
 	do {
 		for (j = 0; j < PROFILE_GRPSZ; ++j) {
 			if (hits[i + j].pc == pc) {
 				hits[i + j].hits += nr_hits;
 				goto out;
 			} else if (!hits[i + j].hits) {
 				hits[i + j].pc = pc;
 				hits[i + j].hits = nr_hits;
 				goto out;
 			}
 		}
 		i = (i + secondary) & (NR_PROFILE_HIT - 1);
 	} while (i != primary);

 	/*
 	 * Add the current hit(s) and flush the write-queue out
 	 * to the global buffer:
 	 */
 	atomic_add(nr_hits, &prof_buffer[pc]);
 	for (i = 0; i < NR_PROFILE_HIT; ++i) {
 		atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 		hits[i].pc = hits[i].hits = 0;
 	}
 out:
 	local_irq_restore(flags);
 	put_cpu();
 }

 static int profile_dead_cpu(unsigned int cpu)
 {
 	struct page *page;
 	int i;

 	if (prof_cpu_mask != NULL)
 		cpumask_clear_cpu(cpu, prof_cpu_mask);

 	for (i = 0; i < 2; i++) {
 		if (per_cpu(cpu_profile_hits, cpu)[i]) {
 			page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
 			per_cpu(cpu_profile_hits, cpu)[i] = NULL;
 			__free_page(page);
 		}
 	}
 	return 0;
 }

 static int profile_prepare_cpu(unsigned int cpu)
 {
 	int i, node = cpu_to_mem(cpu);
 	struct page *page;

 	per_cpu(cpu_profile_flip, cpu) = 0;

 	for (i = 0; i < 2; i++) {
 		if (per_cpu(cpu_profile_hits, cpu)[i])
 			continue;

 		page = __alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 		if (!page) {
 			profile_dead_cpu(cpu);
 			return -ENOMEM;
 		}
 		per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);

 	}
 	return 0;
 }

 static int profile_online_cpu(unsigned int cpu)
 {
 	if (prof_cpu_mask != NULL)
 		cpumask_set_cpu(cpu, prof_cpu_mask);

 	return 0;
 }

 #else /* !CONFIG_SMP */
 #define profile_flip_buffers()		do { } while (0)
 #define profile_discard_flip_buffers()	do { } while (0)

 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 {
 	unsigned long pc;
 	pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 	atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 }
 #endif /* !CONFIG_SMP */

 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 {
 	if (prof_on != type || !prof_buffer)
 		return;
 	do_profile_hits(type, __pc, nr_hits);
 }
 EXPORT_SYMBOL_GPL(profile_hits);

 void profile_tick(int type)
 {
 	struct pt_regs *regs = get_irq_regs();

 	if (!user_mode(regs) && prof_cpu_mask != NULL &&
 	    cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 		profile_hit(type, (void *)profile_pc(regs));
 }

 #ifdef CONFIG_PROC_FS
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
 #include <linux/uaccess.h>

 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 {
 	seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
 	return 0;
 }

 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 {
 	return single_open(file, prof_cpu_mask_proc_show, NULL);
 }

 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 	const char __user *buffer, size_t count, loff_t *pos)
 {
 	cpumask_var_t new_value;
 	int err;

 	if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 		return -ENOMEM;

 	err = cpumask_parse_user(buffer, count, new_value);
 	if (!err) {
 		cpumask_copy(prof_cpu_mask, new_value);
 		err = count;
 	}
 	free_cpumask_var(new_value);
 	return err;
 }

 static const struct file_operations prof_cpu_mask_proc_fops = {
 	.open		= prof_cpu_mask_proc_open,
 	.read		= seq_read,
 	.llseek		= seq_lseek,
 	.release	= single_release,
 	.write		= prof_cpu_mask_proc_write,
 };

 void create_prof_cpu_mask(void)
 {
 	/* create /proc/irq/prof_cpu_mask */
 	proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
 }

 /*
  * This function accesses profiling information. The returned data is
  * binary: the sampling step and the actual contents of the profile
  * buffer. Use of the program readprofile is recommended in order to
  * get meaningful info out of these data.
  */
 static ssize_t
 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
 	unsigned long p = *ppos;
 	ssize_t read;
 	char *pnt;
 	unsigned int sample_step = 1 << prof_shift;

 	profile_flip_buffers();
 	if (p >= (prof_len+1)*sizeof(unsigned int))
 		return 0;
 	if (count > (prof_len+1)*sizeof(unsigned int) - p)
 		count = (prof_len+1)*sizeof(unsigned int) - p;
 	read = 0;

 	while (p < sizeof(unsigned int) && count > 0) {
 		if (put_user(*((char *)(&sample_step)+p), buf))
 			return -EFAULT;
 		buf++; p++; count--; read++;
 	}
 	pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 	if (copy_to_user(buf, (void *)pnt, count))
 		return -EFAULT;
 	read += count;
 	*ppos += read;
 	return read;
 }

 /*
  * Writing to /proc/profile resets the counters
  *
  * Writing a 'profiling multiplier' value into it also re-sets the profiling
  * interrupt frequency, on architectures that support this.
  */
 static ssize_t write_profile(struct file *file, const char __user *buf,
 			     size_t count, loff_t *ppos)
 {
 #ifdef CONFIG_SMP
 	extern int setup_profiling_timer(unsigned int multiplier);

 	if (count == sizeof(int)) {
 		unsigned int multiplier;

 		if (copy_from_user(&multiplier, buf, sizeof(int)))
 			return -EFAULT;

 		if (setup_profiling_timer(multiplier))
 			return -EINVAL;
 	}
 #endif
 	profile_discard_flip_buffers();
 	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 	return count;
 }

 static const struct file_operations proc_profile_operations = {
 	.read		= read_profile,
 	.write		= write_profile,
 	.llseek		= default_llseek,
 };

 int __ref create_proc_profile(void)
 {
 	struct proc_dir_entry *entry;
 #ifdef CONFIG_SMP
 	enum cpuhp_state online_state;
 #endif

 	int err = 0;

 	if (!prof_on)
 		return 0;
 #ifdef CONFIG_SMP
 	err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
 				profile_prepare_cpu, profile_dead_cpu);
 	if (err)
 		return err;

 	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
 				profile_online_cpu, NULL);
 	if (err < 0)
 		goto err_state_prep;
 	online_state = err;
 	err = 0;
 #endif
 	entry = proc_create("profile", S_IWUSR | S_IRUGO,
 			    NULL, &proc_profile_operations);
 	if (!entry)
 		goto err_state_onl;
 	proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));

 	return err;
 err_state_onl:
 #ifdef CONFIG_SMP
 	cpuhp_remove_state(online_state);
 err_state_prep:
 	cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
 #endif
 	return err;
 }
 subsys_initcall(create_proc_profile);
 #endif /* CONFIG_PROC_FS */
	/*
	* linux/kernel/profile.c
	* Simple profiling. Manages a direct-mapped profile hit count buffer,
	* with configurable resolution, support for restricting the cpus on
	* which profiling is done, and switching between cpu time and
	* schedule() calls via kernel command line parameters passed at boot.
	*
	* Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
	* Red Hat, July 2004
	* Consolidation of architecture support code for profiling,
	* Nadia Yvette Chambers, Oracle, July 2004
	* Amortized hit count accounting via per-cpu open-addressed hashtables
	* to resolve timer interrupt livelocks, Nadia Yvette Chambers,
	* Oracle, 2004
	*/

	#include <linux/export.h>
	#include <linux/profile.h>
	#include <linux/memblock.h>
	#include <linux/notifier.h>
	#include <linux/mm.h>
	#include <linux/cpumask.h>
	#include <linux/cpu.h>
	#include <linux/highmem.h>
	#include <linux/mutex.h>
	#include <linux/slab.h>
	#include <linux/vmalloc.h>
	#include <linux/sched/stat.h>

	#include <asm/sections.h>
	#include <asm/irq_regs.h>
	#include <asm/ptrace.h>

	struct profile_hit {
	u32 pc, hits;
	};
	#define PROFILE_GRPSHIFT 3
	#define PROFILE_GRPSZ (1 << PROFILE_GRPSHIFT)
	#define NR_PROFILE_HIT (PAGE_SIZE/sizeof(struct profile_hit))
	#define NR_PROFILE_GRP (NR_PROFILE_HIT/PROFILE_GRPSZ)

	static atomic_t *prof_buffer;
	static unsigned long prof_len, prof_shift;

	int prof_on __read_mostly;
	EXPORT_SYMBOL_GPL(prof_on);

	static cpumask_var_t prof_cpu_mask;
	#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
	static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
	static DEFINE_PER_CPU(int, cpu_profile_flip);
	static DEFINE_MUTEX(profile_flip_mutex);
	#endif /* CONFIG_SMP */

	int profile_setup(char *str)
	{
	static const char schedstr[] = "schedule";
	static const char sleepstr[] = "sleep";
	static const char kvmstr[] = "kvm";
	int par;

	if (!strncmp(str, sleepstr, strlen(sleepstr))) {
	#ifdef CONFIG_SCHEDSTATS
	force_schedstat_enabled();
	prof_on = SLEEP_PROFILING;
	if (str[strlen(sleepstr)] == ',')
	str += strlen(sleepstr) + 1;
	if (get_option(&str, &par))
	prof_shift = par;
	pr_info("kernel sleep profiling enabled (shift: %ld)\n",
	prof_shift);
	#else
	pr_warn("kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
	#endif /* CONFIG_SCHEDSTATS */
	} else if (!strncmp(str, schedstr, strlen(schedstr))) {
	prof_on = SCHED_PROFILING;
	if (str[strlen(schedstr)] == ',')
	str += strlen(schedstr) + 1;
	if (get_option(&str, &par))
	prof_shift = par;
	pr_info("kernel schedule profiling enabled (shift: %ld)\n",
	prof_shift);
	} else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
	prof_on = KVM_PROFILING;
	if (str[strlen(kvmstr)] == ',')
	str += strlen(kvmstr) + 1;
	if (get_option(&str, &par))
	prof_shift = par;
	pr_info("kernel KVM profiling enabled (shift: %ld)\n",
	prof_shift);
	} else if (get_option(&str, &par)) {
	prof_shift = par;
	prof_on = CPU_PROFILING;
	pr_info("kernel profiling enabled (shift: %ld)\n",
	prof_shift);
	}
	return 1;
	}
	__setup("profile=", profile_setup);


	int __ref profile_init(void)
	{
	int buffer_bytes;
	if (!prof_on)
	return 0;

	/* only text is profiled */
	prof_len = (_etext - _stext) >> prof_shift;
	buffer_bytes = prof_len*sizeof(atomic_t);

	if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
	return -ENOMEM;

	cpumask_copy(prof_cpu_mask, cpu_possible_mask);

	prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL\|__GFP_NOWARN);
	if (prof_buffer)
	return 0;

	prof_buffer = alloc_pages_exact(buffer_bytes,
	GFP_KERNEL\|__GFP_ZERO\|__GFP_NOWARN);
	if (prof_buffer)
	return 0;

	prof_buffer = vzalloc(buffer_bytes);
	if (prof_buffer)
	return 0;

	free_cpumask_var(prof_cpu_mask);
	return -ENOMEM;
	}

	/* Profile event notifications */

	static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
	static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
	static BLOCKING_NOTIFIER_HEAD(munmap_notifier);

	void profile_task_exit(struct task_struct *task)
	{
	blocking_notifier_call_chain(&task_exit_notifier, 0, task);
	}

	int profile_handoff_task(struct task_struct *task)
	{
	int ret;
	ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
	return (ret == NOTIFY_OK) ? 1 : 0;
	}

	void profile_munmap(unsigned long addr)
	{
	blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
	}

	int task_handoff_register(struct notifier_block *n)
	{
	return atomic_notifier_chain_register(&task_free_notifier, n);
	}
	EXPORT_SYMBOL_GPL(task_handoff_register);

	int task_handoff_unregister(struct notifier_block *n)
	{
	return atomic_notifier_chain_unregister(&task_free_notifier, n);
	}
	EXPORT_SYMBOL_GPL(task_handoff_unregister);

	int profile_event_register(enum profile_type type, struct notifier_block *n)
	{
	int err = -EINVAL;

	switch (type) {
	case PROFILE_TASK_EXIT:
	err = blocking_notifier_chain_register(
	&task_exit_notifier, n);
	break;
	case PROFILE_MUNMAP:
	err = blocking_notifier_chain_register(
	&munmap_notifier, n);
	break;
	}

	return err;
	}
	EXPORT_SYMBOL_GPL(profile_event_register);

	int profile_event_unregister(enum profile_type type, struct notifier_block *n)
	{
	int err = -EINVAL;

	switch (type) {
	case PROFILE_TASK_EXIT:
	err = blocking_notifier_chain_unregister(
	&task_exit_notifier, n);
	break;
	case PROFILE_MUNMAP:
	err = blocking_notifier_chain_unregister(
	&munmap_notifier, n);
	break;
	}

	return err;
	}
	EXPORT_SYMBOL_GPL(profile_event_unregister);

	#if defined(CONFIG_SMP) && defined(CONFIG_PROC_FS)
	/*
	* Each cpu has a pair of open-addressed hashtables for pending
	* profile hits. read_profile() IPI's all cpus to request them
	* to flip buffers and flushes their contents to prof_buffer itself.
	* Flip requests are serialized by the profile_flip_mutex. The sole
	* use of having a second hashtable is for avoiding cacheline
	* contention that would otherwise happen during flushes of pending
	* profile hits required for the accuracy of reported profile hits
	* and so resurrect the interrupt livelock issue.
	*
	* The open-addressed hashtables are indexed by profile buffer slot
	* and hold the number of pending hits to that profile buffer slot on
	* a cpu in an entry. When the hashtable overflows, all pending hits
	* are accounted to their corresponding profile buffer slots with
	* atomic_add() and the hashtable emptied. As numerous pending hits
	* may be accounted to a profile buffer slot in a hashtable entry,
	* this amortizes a number of atomic profile buffer increments likely
	* to be far larger than the number of entries in the hashtable,
	* particularly given that the number of distinct profile buffer
	* positions to which hits are accounted during short intervals (e.g.
	* several seconds) is usually very small. Exclusion from buffer
	* flipping is provided by interrupt disablement (note that for
	* SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
	* process context).
	* The hash function is meant to be lightweight as opposed to strong,
	* and was vaguely inspired by ppc64 firmware-supported inverted
	* pagetable hash functions, but uses a full hashtable full of finite
	* collision chains, not just pairs of them.
	*
	* -- nyc
	*/
	static void __profile_flip_buffers(void *unused)
	{
	int cpu = smp_processor_id();

	per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
	}

	static void profile_flip_buffers(void)
	{
	int i, j, cpu;

	mutex_lock(&profile_flip_mutex);
	j = per_cpu(cpu_profile_flip, get_cpu());
	put_cpu();
	on_each_cpu(__profile_flip_buffers, NULL, 1);
	for_each_online_cpu(cpu) {
	struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
	for (i = 0; i < NR_PROFILE_HIT; ++i) {
	if (!hits[i].hits) {
	if (hits[i].pc)
	hits[i].pc = 0;
	continue;
	}
	atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
	hits[i].hits = hits[i].pc = 0;
	}
	}
	mutex_unlock(&profile_flip_mutex);
	}

	static void profile_discard_flip_buffers(void)
	{
	int i, cpu;

	mutex_lock(&profile_flip_mutex);
	i = per_cpu(cpu_profile_flip, get_cpu());
	put_cpu();
	on_each_cpu(__profile_flip_buffers, NULL, 1);
	for_each_online_cpu(cpu) {
	struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
	memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
	}
	mutex_unlock(&profile_flip_mutex);
	}

	static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
	{
	unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
	int i, j, cpu;
	struct profile_hit *hits;

	pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
	i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
	secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
	cpu = get_cpu();
	hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
	if (!hits) {
	put_cpu();
	return;
	}
	/*
	* We buffer the global profiler buffer into a per-CPU
	* queue and thus reduce the number of global (and possibly
	* NUMA-alien) accesses. The write-queue is self-coalescing:
	*/
	local_irq_save(flags);
	do {
	for (j = 0; j < PROFILE_GRPSZ; ++j) {
	if (hits[i + j].pc == pc) {
	hits[i + j].hits += nr_hits;
	goto out;
	} else if (!hits[i + j].hits) {
	hits[i + j].pc = pc;
	hits[i + j].hits = nr_hits;
	goto out;
	}
	}
	i = (i + secondary) & (NR_PROFILE_HIT - 1);
	} while (i != primary);

	/*
	* Add the current hit(s) and flush the write-queue out
	* to the global buffer:
	*/
	atomic_add(nr_hits, &prof_buffer[pc]);
	for (i = 0; i < NR_PROFILE_HIT; ++i) {
	atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
	hits[i].pc = hits[i].hits = 0;
	}
	out:
	local_irq_restore(flags);
	put_cpu();
	}

	static int profile_dead_cpu(unsigned int cpu)
	{
	struct page *page;
	int i;

	if (prof_cpu_mask != NULL)
	cpumask_clear_cpu(cpu, prof_cpu_mask);

	for (i = 0; i < 2; i++) {
	if (per_cpu(cpu_profile_hits, cpu)[i]) {
	page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[i]);
	per_cpu(cpu_profile_hits, cpu)[i] = NULL;
	__free_page(page);
	}
	}
	return 0;
	}

	static int profile_prepare_cpu(unsigned int cpu)
	{
	int i, node = cpu_to_mem(cpu);
	struct page *page;

	per_cpu(cpu_profile_flip, cpu) = 0;

	for (i = 0; i < 2; i++) {
	if (per_cpu(cpu_profile_hits, cpu)[i])
	continue;

	page = __alloc_pages_node(node, GFP_KERNEL \| __GFP_ZERO, 0);
	if (!page) {
	profile_dead_cpu(cpu);
	return -ENOMEM;
	}
	per_cpu(cpu_profile_hits, cpu)[i] = page_address(page);

	}
	return 0;
	}

	static int profile_online_cpu(unsigned int cpu)
	{
	if (prof_cpu_mask != NULL)
	cpumask_set_cpu(cpu, prof_cpu_mask);

	return 0;
	}

	#else /* !CONFIG_SMP */
	#define profile_flip_buffers() do { } while (0)
	#define profile_discard_flip_buffers() do { } while (0)

	static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
	{
	unsigned long pc;
	pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
	atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
	}
	#endif /* !CONFIG_SMP */

	void profile_hits(int type, void *__pc, unsigned int nr_hits)
	{
	if (prof_on != type \|\| !prof_buffer)
	return;
	do_profile_hits(type, __pc, nr_hits);
	}
	EXPORT_SYMBOL_GPL(profile_hits);

	void profile_tick(int type)
	{
	struct pt_regs *regs = get_irq_regs();

	if (!user_mode(regs) && prof_cpu_mask != NULL &&
	cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
	profile_hit(type, (void *)profile_pc(regs));
	}

	#ifdef CONFIG_PROC_FS
	#include <linux/proc_fs.h>
	#include <linux/seq_file.h>
	#include <linux/uaccess.h>

	static int prof_cpu_mask_proc_show(struct seq_file m, void v)
	{
	seq_printf(m, "%*pb\n", cpumask_pr_args(prof_cpu_mask));
	return 0;
	}

	static int prof_cpu_mask_proc_open(struct inode inode, struct file file)
	{
	return single_open(file, prof_cpu_mask_proc_show, NULL);
	}

	static ssize_t prof_cpu_mask_proc_write(struct file *file,
	const char __user buffer, size_t count, loff_t pos)
	{
	cpumask_var_t new_value;
	int err;

	if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
	return -ENOMEM;

	err = cpumask_parse_user(buffer, count, new_value);
	if (!err) {
	cpumask_copy(prof_cpu_mask, new_value);
	err = count;
	}
	free_cpumask_var(new_value);
	return err;
	}

	static const struct file_operations prof_cpu_mask_proc_fops = {
	.open = prof_cpu_mask_proc_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
	.write = prof_cpu_mask_proc_write,
	};

	void create_prof_cpu_mask(void)
	{
	/* create /proc/irq/prof_cpu_mask */
	proc_create("irq/prof_cpu_mask", 0600, NULL, &prof_cpu_mask_proc_fops);
	}

	/*
	* This function accesses profiling information. The returned data is
	* binary: the sampling step and the actual contents of the profile
	* buffer. Use of the program readprofile is recommended in order to
	* get meaningful info out of these data.
	*/
	static ssize_t
	read_profile(struct file file, char __user buf, size_t count, loff_t *ppos)
	{
	unsigned long p = *ppos;
	ssize_t read;
	char *pnt;
	unsigned int sample_step = 1 << prof_shift;

	profile_flip_buffers();
	if (p >= (prof_len+1)*sizeof(unsigned int))
	return 0;
	if (count > (prof_len+1)*sizeof(unsigned int) - p)
	count = (prof_len+1)*sizeof(unsigned int) - p;
	read = 0;

	while (p < sizeof(unsigned int) && count > 0) {
	if (put_user(((char )(&sample_step)+p), buf))
	return -EFAULT;
	buf++; p++; count--; read++;
	}
	pnt = (char *)prof_buffer + p - sizeof(atomic_t);
	if (copy_to_user(buf, (void *)pnt, count))
	return -EFAULT;
	read += count;
	*ppos += read;
	return read;
	}

	/*
	* Writing to /proc/profile resets the counters
	*
	* Writing a 'profiling multiplier' value into it also re-sets the profiling
	* interrupt frequency, on architectures that support this.
	*/
	static ssize_t write_profile(struct file file, const char __user buf,
	size_t count, loff_t *ppos)
	{
	#ifdef CONFIG_SMP
	extern int setup_profiling_timer(unsigned int multiplier);

	if (count == sizeof(int)) {
	unsigned int multiplier;

	if (copy_from_user(&multiplier, buf, sizeof(int)))
	return -EFAULT;

	if (setup_profiling_timer(multiplier))
	return -EINVAL;
	}
	#endif
	profile_discard_flip_buffers();
	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
	return count;
	}

	static const struct file_operations proc_profile_operations = {
	.read = read_profile,
	.write = write_profile,
	.llseek = default_llseek,
	};

	int __ref create_proc_profile(void)
	{
	struct proc_dir_entry *entry;
	#ifdef CONFIG_SMP
	enum cpuhp_state online_state;
	#endif

	int err = 0;

	if (!prof_on)
	return 0;
	#ifdef CONFIG_SMP
	err = cpuhp_setup_state(CPUHP_PROFILE_PREPARE, "PROFILE_PREPARE",
	profile_prepare_cpu, profile_dead_cpu);
	if (err)
	return err;

	err = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "AP_PROFILE_ONLINE",
	profile_online_cpu, NULL);
	if (err < 0)
	goto err_state_prep;
	online_state = err;
	err = 0;
	#endif
	entry = proc_create("profile", S_IWUSR \| S_IRUGO,
	NULL, &proc_profile_operations);
	if (!entry)
	goto err_state_onl;
	proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));

	return err;
	err_state_onl:
	#ifdef CONFIG_SMP
	cpuhp_remove_state(online_state);
	err_state_prep:
	cpuhp_remove_state(CPUHP_PROFILE_PREPARE);
	#endif
	return err;
	}
	subsys_initcall(create_proc_profile);
	#endif /* CONFIG_PROC_FS */