<commit_before>/*
 * Generic ring buffer
 *
 * Copyright (C) 2008 <NAME> <<EMAIL>>
 */
#include <linux/ring_buffer.h>
#include <linux/trace_clock.h>
#include <linux/ftrace_irq.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
#include <linux/cpu.h>
#include <linux/fs.h>

#include "trace.h"

/*
 * The ring buffer header is special. We must manually up keep it.
 */
int ring_buffer_print_entry_header(struct trace_seq *s)
{
	int ret;

	ret = trace_seq_printf(s, "\ttype        :    2 bits\n");
	ret = trace_seq_printf(s, "\tlen         :    3 bits\n");
	ret = trace_seq_printf(s, "\ttime_delta  :   27 bits\n");
	ret = trace_seq_printf(s, "\tarray       :   32 bits\n");
	ret = trace_seq_printf(s, "\n");
	ret = trace_seq_printf(s, "\tpadding     : type == %d\n",
			       RINGBUF_TYPE_PADDING);
	ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
			       RINGBUF_TYPE_TIME_EXTEND);
	ret = trace_seq_printf(s, "\tdata        : type == %d\n",
			       RINGBUF_TYPE_DATA);

	return ret;
}

/*
 * 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.
 *
 */

/*
 * A fast way to enable or disable all ring buffers is to
 * call tracing_on or tracing_off. Turning off the ring buffers
 * prevents all ring buffers from being recorded to.
 * Turning this switch on, makes it OK to write to the
 * ring buffer, if the ring buffer is enabled itself.
 *
 * There's three layers that must be on in order to write
 * to the ring buffer.
 *
 * 1) This global flag must be set.
 * 2) The ring buffer must be enabled for recording.
 * 3) The per cpu buffer must be enabled for recording.
 *
 * In case of an anomaly, this global flag has a bit set that
 * will permantly disable all ring buffers.
 */

/*
 * Global flag to disable all recording to ring buffers
 *  This has two bits: ON, DISABLED
 *
 *  ON   DISABLED
 * ---- ----------
 *   0      0        : ring buffers are off
 *   1      0        : ring buffers are on
 *   X      1        : ring buffers are permanently disabled
 */

enum {
	RB_BUFFERS_ON_BIT	= 0,
	RB_BUFFERS_DISABLED_BIT	= 1,
};

enum {
	RB_BUFFERS_ON		= 1 << RB_BUFFERS_ON_BIT,
	RB_BUFFERS_DISABLED	= 1 << RB_BUFFERS_DISABLED_BIT,
};

static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;

#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)

/**
 * tracing_on - enable all tracing buffers
 *
 * This function enables all tracing buffers that may have been
 * disabled with tracing_off.
 */
void tracing_on(void)
{
	set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
EXPORT_SYMBOL_GPL(tracing_on);

/**
 * tracing_off - turn off all tracing buffers
 *
 * This function stops all tracing buffers from recording data.
 * It does not disable any overhead the tracers themselves may
 * be causing. This function simply causes all recording to
 * the ring buffers to fail.
 */
void tracing_off(void)
{
	clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
EXPORT_SYMBOL_GPL(tracing_off);

/**
 * tracing_off_permanent - permanently disable ring buffers
 *
 * This function, once called, will disable all ring buffers
 * permanently.
 */
void tracing_off_permanent(void)
{
	set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
}

/**
 * tracing_is_on - show state of ring buffers enabled
 */
int tracing_is_on(void)
{
	return ring_buffer_flags == RB_BUFFERS_ON;
}
EXPORT_SYMBOL_GPL(tracing_is_on);

#include "trace.h"

#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT		4U
#define RB_MAX_SMALL_DATA	28

enum {
	RB_LEN_TIME_EXTEND = 8,
	RB_LEN_TIME_STAMP = 16,
};

static inline int rb_null_event(struct ring_buffer_event *event)
{
	return event->type == RINGBUF_TYPE_PADDING && event->time_delta == 0;
}

static inline int rb_discarded_event(struct ring_buffer_event *event)
{
	return event->type == RINGBUF_TYPE_PADDING && event->time_delta;
}

static void rb_event_set_padding(struct ring_buffer_event *event)
{
	event->type = RINGBUF_TYPE_PADDING;
	event->time_delta = 0;
}

static unsigned
rb_event_data_length(struct ring_buffer_event *event)
{
	unsigned length;

	if (event->len)
		length = event->len * RB_ALIGNMENT;
	else
		length = event->array[0];
	return length + RB_EVNT_HDR_SIZE;
}

/* inline for ring buffer fast paths */
static unsigned
rb_event_length(struct ring_buffer_event *event)
{
	switch (event->type) {
	case RINGBUF_TYPE_PADDING:
		if (rb_null_event(event))
			/* undefined */
			return -1;
		return rb_event_data_length(event);

	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;
}

/**
 * ring_buffer_event_length - return the length of the event
 * @event: the event to get the length of
 */
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
	unsigned length = rb_event_length(event);
	if (event->type != RINGBUF_TYPE_DATA)
		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 void *
rb_event_data(struct ring_buffer_event *event)
{
	BUG_ON(event->type != RINGBUF_TYPE_DATA);
	/* If length is in len field, then array[0] has the data */
	if (event->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)

struct buffer_data_page {
	u64		 time_stamp;	/* page time stamp */
	local_t		 commit;	/* write committed index */
	unsigned char	 data[];	/* data of buffer page */
};

struct buffer_page {
	local_t		 write;		/* index for next write */
	unsigned	 read;		/* index for next read */
	struct list_head list;		/* list of free pages */
	struct buffer_data_page *page;	/* Actual data page */
};

static void rb_init_page(struct buffer_data_page *bpage)
{
	local_set(&bpage->commit, 0);
}

/**
 * ring_buffer_page_len - the size of data on the page.
 * @page: The page to read
 *
 * Returns the amount of data on the page, including buffer page header.
 */
size_t ring_buffer_page_len(void *page)
{
	return local_read(&((struct buffer_data_page *)page)->commit)
		+ BUF_PAGE_HDR_SIZE;
}

/*
 * Also stolen from mm/slob.c. Thanks to <NAME> 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)

int ring_buffer_print_page_header(struct trace_seq *s)
{
	struct buffer_data_page field;
	int ret;

	ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
			       "offset:0;\tsize:%u;\n",
			       (unsigned int)sizeof(field.time_stamp));

	ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
			       "offset:%u;\tsize:%u;\n",
			       (unsigned int)offsetof(typeof(field), commit),
			       (unsigned int)sizeof(field.commit));

	ret = trace_seq_printf(s, "\tfield: char data;\t"
			       "offset:%u;\tsize:%u;\n",
			       (unsigned int)offsetof(typeof(field), data),
			       (unsigned int)BUF_PAGE_SIZE);

	return ret;
}

/*
 * head_page == tail_page && head == tail then buffer is empty.
 */
struct ring_buffer_per_cpu {
	int				cpu;
	struct ring_buffer		*buffer;
	spinlock_t			reader_lock; /* serialize readers */
	raw_spinlock_t			lock;
	struct lock_class_key		lock_key;
	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			overrun;
	unsigned long			entries;
	u64				write_stamp;
	u64				read_stamp;
	atomic_t			record_disabled;
};

struct ring_buffer {
	unsigned			pages;
	unsigned			flags;
	int				cpus;
	atomic_t			record_disabled;
	cpumask_var_t			cpumask;

	struct mutex			mutex;

	struct ring_buffer_per_cpu	**buffers;

#ifdef CONFIG_HOTPLUG_CPU
	struct notifier_block		cpu_notify;
#endif
	u64				(*clock)(void);
};

struct ring_buffer_iter {
	struct ring_buffer_per_cpu	*cpu_buffer;
	unsigned long			head;
	struct buffer_page		*head_page;
	u64				read_stamp;
};

/* buffer may be either ring_buffer or ring_buffer_per_cpu */
#define RB_WARN_ON(buffer, cond)				\
	({							\
		int _____ret = unlikely(cond);			\
		if (_____ret) {					\
			atomic_inc(&buffer->record_disabled);	\
			WARN_ON(1);				\
		}						\
		_____ret;					\
	})

/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0

u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
{
	u64 time;

	preempt_disable_notrace();
	/* shift to debug/test normalization and TIME_EXTENTS */
	time = buffer->clock() << DEBUG_SHIFT;
	preempt_enable_no_resched_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);

/**
 * 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;

	if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
		return -1;
	if (RB_WARN_ON(cpu_buffer, head->prev->next != 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;
	}

	return 0;
}

static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
			     unsigned nr_pages)
{
	struct list_head *head = &cpu_buffer->pages;
	struct buffer_page *bpage, *tmp;
	unsigned long addr;
	LIST_HEAD(pages);
	unsigned i;

	for (i = 0; i < nr_pages; i++) {
		bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
				    GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
		if (!bpage)
			goto free_pages;
		list_add(&bpage->list, &pages);

		addr = __get_free_page(GFP_KERNEL);
		if (!addr)
			goto free_pages;
		bpage->page = (void *)addr;
		rb_init_page(bpage->page);
	}

	list_splice(&pages, head);

	rb_check_pages(cpu_buffer);

	return 0;

 free_pages:
	list_for_each_entry_safe(bpage, tmp, &pages, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	return -ENOMEM;
}

static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
{
	struct ring_buffer_per_cpu *cpu_buffer;
	struct buffer_page *bpage;
	unsigned long addr;
	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;
	spin_lock_init(&cpu_buffer->reader_lock);
	cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
	INIT_LIST_HEAD(&cpu_buffer->pages);

	bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
			    GFP_KERNEL, cpu_to_node(cpu));
	if (!bpage)
		goto fail_free_buffer;

	cpu_buffer->reader_page = bpage;
	addr = __get_free_page(GFP_KERNEL);
	if (!addr)
		goto fail_free_reader;
	bpage->page = (void *)addr;
	rb_init_page(bpage->page);

	INIT_LIST_HEAD(&cpu_buffer->reader_page->list);

	ret = rb_allocate_pages(cpu_buffer, buffer->pages);
	if (ret < 0)
		goto fail_free_reader;

	cpu_buffer->head_page
		= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
	cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;

	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);

	list_for_each_entry_safe(bpage, tmp, head, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	kfree(cpu_buffer);
}

/*
 * Causes compile errors if the struct buffer_page gets bigger
 * than the struct page.
 */
extern int ring_buffer_page_too_big(void);

#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
			 unsigned long action, void *hcpu);
#endif

/**
 * 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 ring_buffer *buffer;
	int bsize;
	int cpu;

	/* Paranoid! Optimizes out when all is well */
	if (sizeof(struct buffer_page) > sizeof(struct page))
		ring_buffer_page_too_big();


	/* keep it in its own cache line */
	buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
			 GFP_KERNEL);
	if (!buffer)
		return NULL;

	if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
		goto fail_free_buffer;

	buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
	buffer->flags = flags;
	buffer->clock = trace_clock_local;

	/* need at least two pages */
	if (buffer->pages == 1)
		buffer->pages++;

	/*
	 * In case of non-hotplug cpu, if the ring-buffer is allocated
	 * in early initcall, it will not be notified of secondary cpus.
	 * In that off case, we need to allocate for all possible cpus.
	 */
#ifdef CONFIG_HOTPLUG_CPU
	get_online_cpus();
	cpumask_copy(buffer->cpumask, cpu_online_mask);
#else
	cpumask_copy(buffer->cpumask, cpu_possible_mask);
#endif
	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;

	for_each_buffer_cpu(buffer, cpu) {
		buffer->buffers[cpu] =
			rb_allocate_cpu_buffer(buffer, cpu);
		if (!buffer->buffers[cpu])
			goto fail_free_buffers;
	}

#ifdef CONFIG_HOTPLUG_CPU
	buffer->cpu_notify.notifier_call = rb_cpu_notify;
	buffer->cpu_notify.priority = 0;
	register_cpu_notifier(&buffer->cpu_notify);
#endif

	put_online_cpus();
	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);
	put_online_cpus();

 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;

	get_online_cpus();

#ifdef CONFIG_HOTPLUG_CPU
	unregister_cpu_notifier(&buffer->cpu_notify);
#endif

	for_each_buffer_cpu(buffer, cpu)
		rb_free_cpu_buffer(buffer->buffers[cpu]);

	put_online_cpus();

	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;
}

static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);

static void
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
{
	struct buffer_page *bpage;
	struct list_head *p;
	unsigned i;

	atomic_inc(&cpu_buffer->record_disabled);
	synchronize_sched();

	for (i = 0; i < nr_pages; i++) {
		if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
			return;
		p = cpu_buffer->pages.next;
		bpage = list_entry(p, struct buffer_page, list);
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
		return;

	rb_reset_cpu(cpu_buffer);

	rb_check_pages(cpu_buffer);

	atomic_dec(&cpu_buffer->record_disabled);

}

static void
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
		struct list_head *pages, unsigned nr_pages)
{
	struct buffer_page *bpage;
	struct list_head *p;
	unsigned i;

	atomic_inc(&cpu_buffer->record_disabled);
	synchronize_sched();

	for (i = 0; i < nr_pages; i++) {
		if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
			return;
		p = pages->next;
		bpage = list_entry(p, struct buffer_page, list);
		list_del_init(&bpage->list);
		list_add_tail(&bpage->list, &cpu_buffer->pages);
	}
	rb_reset_cpu(cpu_buffer);

	rb_check_pages(cpu_buffer);

	atomic_dec(&cpu_buffer->record_disabled);
}

/**
 * ring_buffer_resize - resize the ring buffer
 * @buffer: the buffer to resize.
 * @size: the new size.
 *
 * The tracer is responsible for making sure that the buffer is
 * not being used while changing the size.
 * Note: We may be able to change the above requirement by using
 *  RCU synchronizations.
 *
 * Minimum size is 2 * BUF_PAGE_SIZE.
 *
 * Returns -1 on failure.
 */
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
{
	struct ring_buffer_per_cpu *cpu_buffer;
	unsigned nr_pages, rm_pages, new_pages;
	struct buffer_page *bpage, *tmp;
	unsigned long buffer_size;
	unsigned long addr;
	LIST_HEAD(pages);
	int i, cpu;

	/*
	 * Always succeed at resizing a non-existent buffer:
	 */
	if (!buffer)
		return size;

	size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
	size *= BUF_PAGE_SIZE;
	buffer_size = buffer->pages * BUF_PAGE_SIZE;

	/* we need a minimum of two pages */
	if (size < BUF_PAGE_SIZE * 2)
		size = BUF_PAGE_SIZE * 2;

	if (size == buffer_size)
		return size;

	mutex_lock(&buffer->mutex);
	get_online_cpus();

	nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);

	if (size < buffer_size) {

		/* easy case, just free pages */
		if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
			goto out_fail;

		rm_pages = buffer->pages - nr_pages;

		for_each_buffer_cpu(buffer, cpu) {
			cpu_buffer = buffer->buffers[cpu];
			rb_remove_pages(cpu_buffer, rm_pages);
		}
		goto out;
	}

	/*
	 * This is a bit more difficult. We only want to add pages
	 * when we can allocate enough for all CPUs. We do this
	 * by allocating all the pages and storing them on a local
	 * link list. If we succeed in our allocation, then we
	 * add these pages to the cpu_buffers. Otherwise we just free
	 * them all and return -ENOMEM;
	 */
	if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
		goto out_fail;

	new_pages = nr_pages - buffer->pages;

	for_each_buffer_cpu(buffer, cpu) {
		for (i = 0; i < new_pages; i++) {
			bpage = kzalloc_node(ALIGN(sizeof(*bpage),
						  cache_line_size()),
					    GFP_KERNEL, cpu_to_node(cpu));
			if (!bpage)
				goto free_pages;
			list_add(&bpage->list, &pages);
			addr = __get_free_page(GFP_KERNEL);
			if (!addr)
				goto free_pages;
			bpage->page = (void *)addr;
			rb_init_page(bpage->page);
		}
	}

	for_each_buffer_cpu(buffer, cpu) {
		cpu_buffer = buffer->buffers[cpu];
		rb_insert_pages(cpu_buffer, &pages, new_pages);
	}

	if (RB_WARN_ON(buffer, !list_empty(&pages)))
		goto out_fail;

 out:
	buffer->pages = nr_pages;
	put_online_cpus();
	mutex_unlock(&buffer->mutex);

	return size;

 free_pages:
	list_for_each_entry_safe(bpage, tmp, &pages, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	put_online_cpus();
	mutex_unlock(&buffer->mutex);
	return -ENOMEM;

	/*
	 * Something went totally wrong, and we are too paranoid
	 * to even clean up the mess.
	 */
 out_fail:
	put_online_cpus();
	mutex_unlock(&buffer->mutex);
	return -1;
}
EXPORT_SYMBOL_GPL(ring_buffer_resize);

static inline void *
__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
{
	return bpage->data + index;
}

static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
{
	return bpage->page->data + index;
}

static 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 inline struct ring_buffer_event *
rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
{
	return __rb_page_index(cpu_buffer->head_page,
			       cpu_buffer->head_page->read);
}

static inline struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter *iter)
{
	return __rb_page_index(iter->head_page, iter->head);
}

static inline unsigned rb_page_write(struct buffer_page *bpage)
{
	return local_read(&bpage->write);
}

static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
	return local_read(&bpage->page->commit);
}

/* Size is determined by what has been commited */
static inline unsigned rb_page_size(struct buffer_page *bpage)
{
	return rb_page_commit(bpage);
}

static inline unsigned
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
{
	return rb_page_commit(cpu_buffer->commit_page);
}

static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
{
	return rb_page_commit(cpu_buffer->head_page);
}

/*
 * When the tail hits the head and the buffer is in overwrite mode,
 * the head jumps to the next page and all content on the previous
 * page is discarded. But before doing so, we update the overrun
 * variable of the buffer.
 */
static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
{
	struct ring_buffer_event *event;
	unsigned long head;

	for (head = 0; head < rb_head_size(cpu_buffer);
	     head += rb_event_length(event)) {

		event = __rb_page_index(cpu_buffer->head_page, head);
		if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
			return;
		/* Only count data entries */
		if (event->type != RINGBUF_TYPE_DATA)
			continue;
		cpu_buffer->overrun++;
		cpu_buffer->entries--;
	}
}

static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
			       struct buffer_page **bpage)
{
	struct list_head *p = (*bpage)->list.next;

	if (p == &cpu_buffer->pages)
		p = p->next;

	*bpage = list_entry(p, struct buffer_page, list);
}

static inline unsigned
rb_event_index(struct ring_buffer_event *event)
{
	unsigned long addr = (unsigned long)event;

	return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
}

static int
rb_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 void
rb_set_commit_event(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;

	while (cpu_buffer->commit_page->page != (void *)addr) {
		if (RB_WARN_ON(cpu_buffer,
			  cpu_buffer->commit_page == cpu_buffer->tail_page))
			return;
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
		cpu_buffer->write_stamp =
			cpu_buffer->commit_page->page->time_stamp;
	}

	/* Now set the commit to the event's index */
	local_set(&cpu_buffer->commit_page->page->commit, index);
}

static void
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
{
	/*
	 * 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:
	while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		rb_inc_page(cpu_buffer, &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)) {
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		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 != cpu_buffer->tail_page))
		goto again;
}

static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
	cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
	cpu_buffer->reader_page->read = 0;
}

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 = cpu_buffer->head_page;
	else
		rb_inc_page(cpu_buffer, &iter->head_page);

	iter->read_stamp = iter->head_page->page->time_stamp;
	iter->head = 0;
}

/**
 * ring_buffer_update_event - update event type and data
 * @event: the even 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_event *event,
			 unsigned type, unsigned length)
{
	event->type = type;

	switch (type) {

	case RINGBUF_TYPE_PADDING:
		break;

	case RINGBUF_TYPE_TIME_EXTEND:
		event->len = DIV_ROUND_UP(RB_LEN_TIME_EXTEND, RB_ALIGNMENT);
		break;

	case RINGBUF_TYPE_TIME_STAMP:
		event->len = DIV_ROUND_UP(RB_LEN_TIME_STAMP, RB_ALIGNMENT);
		break;

	case RINGBUF_TYPE_DATA:
		length -= RB_EVNT_HDR_SIZE;
		if (length > RB_MAX_SMALL_DATA) {
			event->len = 0;
			event->array[0] = length;
		} else
			event->len = DIV_ROUND_UP(length, RB_ALIGNMENT);
		break;
	default:
		BUG();
	}
}

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 = 1;

	if (length > RB_MAX_SMALL_DATA)
		length += sizeof(event.array[0]);

	length += RB_EVNT_HDR_SIZE;
	length = ALIGN(length, RB_ALIGNMENT);

	return length;
}

static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
		  unsigned type, unsigned long length, u64 *ts)
{
	struct buffer_page *tail_page, *head_page, *reader_page, *commit_page;
	unsigned long tail, write;
	struct ring_buffer *buffer = cpu_buffer->buffer;
	struct ring_buffer_event *event;
	unsigned long flags;
	bool lock_taken = false;

	commit_page = cpu_buffer->commit_page;
	/* we just need to protect against interrupts */
	barrier();
	tail_page = cpu_buffer->tail_page;
	write = local_add_return(length, &tail_page->write);
	tail = write - length;

	/* See if we shot pass the end of this buffer page */
	if (write > BUF_PAGE_SIZE) {
		struct buffer_page *next_page = tail_page;

		local_irq_save(flags);
		/*
		 * Since the write to the buffer is still not
		 * fully lockless, we must be careful with NMIs.
		 * The locks in the writers are taken when a write
		 * crosses to a new page. The locks protect against
		 * races with the readers (this will soon be fixed
		 * with a lockless solution).
		 *
		 * Because we can not protect against NMIs, and we
		 * want to keep traces reentrant, we need to manage
		 * what happens when we are in an NMI.
		 *
		 * NMIs can happen after we take the lock.
		 * If we are in an NMI, only take the lock
		 * if it is not already taken. Otherwise
		 * simply fail.
		 */
		if (unlikely(in_nmi())) {
			if (!__raw_spin_trylock(&cpu_buffer->lock))
				goto out_reset;
		} else
			__raw_spin_lock(&cpu_buffer->lock);

		lock_taken = true;

		rb_inc_page(cpu_buffer, &next_page);

		head_page = cpu_buffer->head_page;
		reader_page = cpu_buffer->reader_page;

		/* we grabbed the lock before incrementing */
		if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
			goto out_reset;

		/*
		 * 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)) {
			WARN_ON_ONCE(1);
			goto out_reset;
		}

		if (next_page == head_page) {
			if (!(buffer->flags & RB_FL_OVERWRITE))
				goto out_reset;

			/* tail_page has not moved yet? */
			if (tail_page == cpu_buffer->tail_page) {
				/* count overflows */
				rb_update_overflow(cpu_buffer);

				rb_inc_page(cpu_buffer, &head_page);
				cpu_buffer->head_page = head_page;
				cpu_buffer->head_page->read = 0;
			}
		}

		/*
		 * 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 == cpu_buffer->tail_page) {
			local_set(&next_page->write, 0);
			local_set(&next_page->page->commit, 0);
			cpu_buffer->tail_page = next_page;

			/* reread the time stamp */
			*ts = ring_buffer_time_stamp(buffer, cpu_buffer->cpu);
			cpu_buffer->tail_page->page->time_stamp = *ts;
		}

		/*
		 * The actual tail page has moved forward.
		 */
		if (tail < BUF_PAGE_SIZE) {
			/* Mark the rest of the page with padding */
			event = __rb_page_index(tail_page, tail);
			rb_event_set_padding(event);
		}

		if (tail <= BUF_PAGE_SIZE)
			/* Set the write back to the previous setting */
			local_set(&tail_page->write, tail);

		/*
		 * If this was a commit entry that failed,
		 * increment that too
		 */
		if (tail_page == cpu_buffer->commit_page &&
		    tail == rb_commit_index(cpu_buffer)) {
			rb_set_commit_to_write(cpu_buffer);
		}

		__raw_spin_unlock(&cpu_buffer->lock);
		local_irq_restore(flags);

		/* fail and let the caller try again */
		return ERR_PTR(-EAGAIN);
	}

	/* We reserved something on the buffer */

	if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
		return NULL;

	event = __rb_page_index(tail_page, tail);
	rb_update_event(event, type, length);

	/*
	 * If this is a commit and the tail is zero, then update
	 * this page's time stamp.
	 */
	if (!tail && rb_is_commit(cpu_buffer, event))
		cpu_buffer->commit_page->page->time_stamp = *ts;

	return event;

 out_reset:
	/* reset write */
	if (tail <= BUF_PAGE_SIZE)
		local_set(&tail_page->write, tail);

	if (likely(lock_taken))
		__raw_spin_unlock(&cpu_buffer->lock);
	local_irq_restore(flags);
	return NULL;
}

static int
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
		  u64 *ts, u64 *delta)
{
	struct ring_buffer_event *event;
	static int once;
	int ret;

	if (unlikely(*delta > (1ULL << 59) && !once++)) {
		printk(KERN_WARNING "Delta way too big! %llu"
		       " ts=%llu write stamp = %llu\n",
		       (unsigned long long)*delta,
		       (unsigned long long)*ts,
		       (unsigned long long)cpu_buffer->write_stamp);
		WARN_ON(1);
	}

	/*
	 * The delta is too big, we to add a
	 * new timestamp.
	 */
	event = __rb_reserve_next(cpu_buffer,
				  RINGBUF_TYPE_TIME_EXTEND,
				  RB_LEN_TIME_EXTEND,
				  ts);
	if (!event)
		return -EBUSY;

	if (PTR_ERR(event) == -EAGAIN)
		return -EAGAIN;

	/* Only a commited time event can update the write stamp */
	if (rb_is_commit(cpu_buffer, event)) {
		/*
		 * If this is the first on the page, then we need to
		 * update the page itself, and just put in a zero.
		 */
		if (rb_event_index(event)) {
			event->time_delta = *delta & TS_MASK;
			event->array[0] = *delta >> TS_SHIFT;
		} else {
			cpu_buffer->commit_page->page->time_stamp = *ts;
			event->time_delta = 0;
			event->array[0] = 0;
		}
		cpu_buffer->write_stamp = *ts;
		/* let the caller know this was the commit */
		ret = 1;
	} else {
		/* Darn, this is just wasted space */
		event->time_delta = 0;
		event->array[0] = 0;
		ret = 0;
	}

	*delta = 0;

	return ret;
}

static struct ring_buffer_event *
rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
		      unsigned type, unsigned long length)
{
	struct ring_buffer_event *event;
	u64 ts, delta;
	int commit = 0;
	int nr_loops = 0;

 again:
	/*
	 * 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))
		return NULL;

	ts = ring_buffer_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);

	/*
	 * Only the first commit can update the timestamp.
	 * Yes there is a race here. If an interrupt comes in
	 * just after the conditional and it traces too, then it
	 * will also check the deltas. More than one timestamp may
	 * also be made. But only the entry that did the actual
	 * commit will be something other than zero.
	 */
	if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
	    rb_page_write(cpu_buffer->tail_page) ==
	    rb_commit_index(cpu_buffer)) {

		delta = ts - cpu_buffer->write_stamp;

		/* make sure this delta is calculated here */
		barrier();

		/* Did the write stamp get updated already? */
		if (unlikely(ts < cpu_buffer->write_stamp))
			delta = 0;

		if (test_time_stamp(delta)) {

			commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);

			if (commit == -EBUSY)
				return NULL;

			if (commit == -EAGAIN)
				goto again;

			RB_WARN_ON(cpu_buffer, commit < 0);
		}
	} else
		/* Non commits have zero deltas */
		delta = 0;

	event = __rb_reserve_next(cpu_buffer, type, length, &ts);
	if (PTR_ERR(event) == -EAGAIN)
		goto again;

	if (!event) {
		if (unlikely(commit))
			/*
			 * Ouch! We needed a timestamp and it was commited. But
			 * we didn't get our event reserved.
			 */
			rb_set_commit_to_write(cpu_buffer);
		return NULL;
	}

	/*
	 * If the timestamp was commited, make the commit our entry
	 * now so that we will update it when needed.
	 */
	if (commit)
		rb_set_commit_event(cpu_buffer, event);
	else if (!rb_is_commit(cpu_buffer, event))
		delta = 0;

	event->time_delta = delta;

	return event;
}

static int trace_irq_level(void)
{
	return hardirq_count() + softirq_count() + in_nmi();
}

static int trace_recursive_lock(void)
{
	int level;

	level = trace_irq_level();

	if (unlikely(current->trace_recursion & (1 << level))) {
		/* Disable all tracing before we do anything else */
		tracing_off_permanent();
		WARN_ON_ONCE(1);
		return -1;
	}

	current->trace_recursion |= 1 << level;

	return 0;
}

static void trace_recursive_unlock(void)
{
	int level;

	level = trace_irq_level();

	WARN_ON_ONCE(!current->trace_recursion & (1 << level));

	current->trace_recursion &= ~(1 << level);
}

static DEFINE_PER_CPU(int, rb_need_resched);

/**<commit_msg>tracing/core: Add current context on tracing recursion warning<commit_after>/*
 * Generic ring buffer
 *
 * Copyright (C) 2008 <NAME> <<EMAIL>>
 */
#include <linux/ring_buffer.h>
#include <linux/trace_clock.h>
#include <linux/ftrace_irq.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/hardirq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
#include <linux/cpu.h>
#include <linux/fs.h>

#include "trace.h"

/*
 * The ring buffer header is special. We must manually up keep it.
 */
int ring_buffer_print_entry_header(struct trace_seq *s)
{
	int ret;

	ret = trace_seq_printf(s, "\ttype        :    2 bits\n");
	ret = trace_seq_printf(s, "\tlen         :    3 bits\n");
	ret = trace_seq_printf(s, "\ttime_delta  :   27 bits\n");
	ret = trace_seq_printf(s, "\tarray       :   32 bits\n");
	ret = trace_seq_printf(s, "\n");
	ret = trace_seq_printf(s, "\tpadding     : type == %d\n",
			       RINGBUF_TYPE_PADDING);
	ret = trace_seq_printf(s, "\ttime_extend : type == %d\n",
			       RINGBUF_TYPE_TIME_EXTEND);
	ret = trace_seq_printf(s, "\tdata        : type == %d\n",
			       RINGBUF_TYPE_DATA);

	return ret;
}

/*
 * 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.
 *
 */

/*
 * A fast way to enable or disable all ring buffers is to
 * call tracing_on or tracing_off. Turning off the ring buffers
 * prevents all ring buffers from being recorded to.
 * Turning this switch on, makes it OK to write to the
 * ring buffer, if the ring buffer is enabled itself.
 *
 * There's three layers that must be on in order to write
 * to the ring buffer.
 *
 * 1) This global flag must be set.
 * 2) The ring buffer must be enabled for recording.
 * 3) The per cpu buffer must be enabled for recording.
 *
 * In case of an anomaly, this global flag has a bit set that
 * will permantly disable all ring buffers.
 */

/*
 * Global flag to disable all recording to ring buffers
 *  This has two bits: ON, DISABLED
 *
 *  ON   DISABLED
 * ---- ----------
 *   0      0        : ring buffers are off
 *   1      0        : ring buffers are on
 *   X      1        : ring buffers are permanently disabled
 */

enum {
	RB_BUFFERS_ON_BIT	= 0,
	RB_BUFFERS_DISABLED_BIT	= 1,
};

enum {
	RB_BUFFERS_ON		= 1 << RB_BUFFERS_ON_BIT,
	RB_BUFFERS_DISABLED	= 1 << RB_BUFFERS_DISABLED_BIT,
};

static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;

#define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data)

/**
 * tracing_on - enable all tracing buffers
 *
 * This function enables all tracing buffers that may have been
 * disabled with tracing_off.
 */
void tracing_on(void)
{
	set_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
EXPORT_SYMBOL_GPL(tracing_on);

/**
 * tracing_off - turn off all tracing buffers
 *
 * This function stops all tracing buffers from recording data.
 * It does not disable any overhead the tracers themselves may
 * be causing. This function simply causes all recording to
 * the ring buffers to fail.
 */
void tracing_off(void)
{
	clear_bit(RB_BUFFERS_ON_BIT, &ring_buffer_flags);
}
EXPORT_SYMBOL_GPL(tracing_off);

/**
 * tracing_off_permanent - permanently disable ring buffers
 *
 * This function, once called, will disable all ring buffers
 * permanently.
 */
void tracing_off_permanent(void)
{
	set_bit(RB_BUFFERS_DISABLED_BIT, &ring_buffer_flags);
}

/**
 * tracing_is_on - show state of ring buffers enabled
 */
int tracing_is_on(void)
{
	return ring_buffer_flags == RB_BUFFERS_ON;
}
EXPORT_SYMBOL_GPL(tracing_is_on);

#include "trace.h"

#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT		4U
#define RB_MAX_SMALL_DATA	28

enum {
	RB_LEN_TIME_EXTEND = 8,
	RB_LEN_TIME_STAMP = 16,
};

static inline int rb_null_event(struct ring_buffer_event *event)
{
	return event->type == RINGBUF_TYPE_PADDING && event->time_delta == 0;
}

static inline int rb_discarded_event(struct ring_buffer_event *event)
{
	return event->type == RINGBUF_TYPE_PADDING && event->time_delta;
}

static void rb_event_set_padding(struct ring_buffer_event *event)
{
	event->type = RINGBUF_TYPE_PADDING;
	event->time_delta = 0;
}

static unsigned
rb_event_data_length(struct ring_buffer_event *event)
{
	unsigned length;

	if (event->len)
		length = event->len * RB_ALIGNMENT;
	else
		length = event->array[0];
	return length + RB_EVNT_HDR_SIZE;
}

/* inline for ring buffer fast paths */
static unsigned
rb_event_length(struct ring_buffer_event *event)
{
	switch (event->type) {
	case RINGBUF_TYPE_PADDING:
		if (rb_null_event(event))
			/* undefined */
			return -1;
		return rb_event_data_length(event);

	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;
}

/**
 * ring_buffer_event_length - return the length of the event
 * @event: the event to get the length of
 */
unsigned ring_buffer_event_length(struct ring_buffer_event *event)
{
	unsigned length = rb_event_length(event);
	if (event->type != RINGBUF_TYPE_DATA)
		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 void *
rb_event_data(struct ring_buffer_event *event)
{
	BUG_ON(event->type != RINGBUF_TYPE_DATA);
	/* If length is in len field, then array[0] has the data */
	if (event->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)

struct buffer_data_page {
	u64		 time_stamp;	/* page time stamp */
	local_t		 commit;	/* write committed index */
	unsigned char	 data[];	/* data of buffer page */
};

struct buffer_page {
	local_t		 write;		/* index for next write */
	unsigned	 read;		/* index for next read */
	struct list_head list;		/* list of free pages */
	struct buffer_data_page *page;	/* Actual data page */
};

static void rb_init_page(struct buffer_data_page *bpage)
{
	local_set(&bpage->commit, 0);
}

/**
 * ring_buffer_page_len - the size of data on the page.
 * @page: The page to read
 *
 * Returns the amount of data on the page, including buffer page header.
 */
size_t ring_buffer_page_len(void *page)
{
	return local_read(&((struct buffer_data_page *)page)->commit)
		+ BUF_PAGE_HDR_SIZE;
}

/*
 * Also stolen from mm/slob.c. Thanks to <NAME> 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)

int ring_buffer_print_page_header(struct trace_seq *s)
{
	struct buffer_data_page field;
	int ret;

	ret = trace_seq_printf(s, "\tfield: u64 timestamp;\t"
			       "offset:0;\tsize:%u;\n",
			       (unsigned int)sizeof(field.time_stamp));

	ret = trace_seq_printf(s, "\tfield: local_t commit;\t"
			       "offset:%u;\tsize:%u;\n",
			       (unsigned int)offsetof(typeof(field), commit),
			       (unsigned int)sizeof(field.commit));

	ret = trace_seq_printf(s, "\tfield: char data;\t"
			       "offset:%u;\tsize:%u;\n",
			       (unsigned int)offsetof(typeof(field), data),
			       (unsigned int)BUF_PAGE_SIZE);

	return ret;
}

/*
 * head_page == tail_page && head == tail then buffer is empty.
 */
struct ring_buffer_per_cpu {
	int				cpu;
	struct ring_buffer		*buffer;
	spinlock_t			reader_lock; /* serialize readers */
	raw_spinlock_t			lock;
	struct lock_class_key		lock_key;
	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			overrun;
	unsigned long			entries;
	u64				write_stamp;
	u64				read_stamp;
	atomic_t			record_disabled;
};

struct ring_buffer {
	unsigned			pages;
	unsigned			flags;
	int				cpus;
	atomic_t			record_disabled;
	cpumask_var_t			cpumask;

	struct mutex			mutex;

	struct ring_buffer_per_cpu	**buffers;

#ifdef CONFIG_HOTPLUG_CPU
	struct notifier_block		cpu_notify;
#endif
	u64				(*clock)(void);
};

struct ring_buffer_iter {
	struct ring_buffer_per_cpu	*cpu_buffer;
	unsigned long			head;
	struct buffer_page		*head_page;
	u64				read_stamp;
};

/* buffer may be either ring_buffer or ring_buffer_per_cpu */
#define RB_WARN_ON(buffer, cond)				\
	({							\
		int _____ret = unlikely(cond);			\
		if (_____ret) {					\
			atomic_inc(&buffer->record_disabled);	\
			WARN_ON(1);				\
		}						\
		_____ret;					\
	})

/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0

u64 ring_buffer_time_stamp(struct ring_buffer *buffer, int cpu)
{
	u64 time;

	preempt_disable_notrace();
	/* shift to debug/test normalization and TIME_EXTENTS */
	time = buffer->clock() << DEBUG_SHIFT;
	preempt_enable_no_resched_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);

/**
 * 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;

	if (RB_WARN_ON(cpu_buffer, head->next->prev != head))
		return -1;
	if (RB_WARN_ON(cpu_buffer, head->prev->next != 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;
	}

	return 0;
}

static int rb_allocate_pages(struct ring_buffer_per_cpu *cpu_buffer,
			     unsigned nr_pages)
{
	struct list_head *head = &cpu_buffer->pages;
	struct buffer_page *bpage, *tmp;
	unsigned long addr;
	LIST_HEAD(pages);
	unsigned i;

	for (i = 0; i < nr_pages; i++) {
		bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
				    GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
		if (!bpage)
			goto free_pages;
		list_add(&bpage->list, &pages);

		addr = __get_free_page(GFP_KERNEL);
		if (!addr)
			goto free_pages;
		bpage->page = (void *)addr;
		rb_init_page(bpage->page);
	}

	list_splice(&pages, head);

	rb_check_pages(cpu_buffer);

	return 0;

 free_pages:
	list_for_each_entry_safe(bpage, tmp, &pages, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	return -ENOMEM;
}

static struct ring_buffer_per_cpu *
rb_allocate_cpu_buffer(struct ring_buffer *buffer, int cpu)
{
	struct ring_buffer_per_cpu *cpu_buffer;
	struct buffer_page *bpage;
	unsigned long addr;
	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;
	spin_lock_init(&cpu_buffer->reader_lock);
	cpu_buffer->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
	INIT_LIST_HEAD(&cpu_buffer->pages);

	bpage = kzalloc_node(ALIGN(sizeof(*bpage), cache_line_size()),
			    GFP_KERNEL, cpu_to_node(cpu));
	if (!bpage)
		goto fail_free_buffer;

	cpu_buffer->reader_page = bpage;
	addr = __get_free_page(GFP_KERNEL);
	if (!addr)
		goto fail_free_reader;
	bpage->page = (void *)addr;
	rb_init_page(bpage->page);

	INIT_LIST_HEAD(&cpu_buffer->reader_page->list);

	ret = rb_allocate_pages(cpu_buffer, buffer->pages);
	if (ret < 0)
		goto fail_free_reader;

	cpu_buffer->head_page
		= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
	cpu_buffer->tail_page = cpu_buffer->commit_page = cpu_buffer->head_page;

	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);

	list_for_each_entry_safe(bpage, tmp, head, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	kfree(cpu_buffer);
}

/*
 * Causes compile errors if the struct buffer_page gets bigger
 * than the struct page.
 */
extern int ring_buffer_page_too_big(void);

#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
			 unsigned long action, void *hcpu);
#endif

/**
 * 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 ring_buffer *buffer;
	int bsize;
	int cpu;

	/* Paranoid! Optimizes out when all is well */
	if (sizeof(struct buffer_page) > sizeof(struct page))
		ring_buffer_page_too_big();


	/* keep it in its own cache line */
	buffer = kzalloc(ALIGN(sizeof(*buffer), cache_line_size()),
			 GFP_KERNEL);
	if (!buffer)
		return NULL;

	if (!alloc_cpumask_var(&buffer->cpumask, GFP_KERNEL))
		goto fail_free_buffer;

	buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
	buffer->flags = flags;
	buffer->clock = trace_clock_local;

	/* need at least two pages */
	if (buffer->pages == 1)
		buffer->pages++;

	/*
	 * In case of non-hotplug cpu, if the ring-buffer is allocated
	 * in early initcall, it will not be notified of secondary cpus.
	 * In that off case, we need to allocate for all possible cpus.
	 */
#ifdef CONFIG_HOTPLUG_CPU
	get_online_cpus();
	cpumask_copy(buffer->cpumask, cpu_online_mask);
#else
	cpumask_copy(buffer->cpumask, cpu_possible_mask);
#endif
	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;

	for_each_buffer_cpu(buffer, cpu) {
		buffer->buffers[cpu] =
			rb_allocate_cpu_buffer(buffer, cpu);
		if (!buffer->buffers[cpu])
			goto fail_free_buffers;
	}

#ifdef CONFIG_HOTPLUG_CPU
	buffer->cpu_notify.notifier_call = rb_cpu_notify;
	buffer->cpu_notify.priority = 0;
	register_cpu_notifier(&buffer->cpu_notify);
#endif

	put_online_cpus();
	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);
	put_online_cpus();

 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;

	get_online_cpus();

#ifdef CONFIG_HOTPLUG_CPU
	unregister_cpu_notifier(&buffer->cpu_notify);
#endif

	for_each_buffer_cpu(buffer, cpu)
		rb_free_cpu_buffer(buffer->buffers[cpu]);

	put_online_cpus();

	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;
}

static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);

static void
rb_remove_pages(struct ring_buffer_per_cpu *cpu_buffer, unsigned nr_pages)
{
	struct buffer_page *bpage;
	struct list_head *p;
	unsigned i;

	atomic_inc(&cpu_buffer->record_disabled);
	synchronize_sched();

	for (i = 0; i < nr_pages; i++) {
		if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
			return;
		p = cpu_buffer->pages.next;
		bpage = list_entry(p, struct buffer_page, list);
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	if (RB_WARN_ON(cpu_buffer, list_empty(&cpu_buffer->pages)))
		return;

	rb_reset_cpu(cpu_buffer);

	rb_check_pages(cpu_buffer);

	atomic_dec(&cpu_buffer->record_disabled);

}

static void
rb_insert_pages(struct ring_buffer_per_cpu *cpu_buffer,
		struct list_head *pages, unsigned nr_pages)
{
	struct buffer_page *bpage;
	struct list_head *p;
	unsigned i;

	atomic_inc(&cpu_buffer->record_disabled);
	synchronize_sched();

	for (i = 0; i < nr_pages; i++) {
		if (RB_WARN_ON(cpu_buffer, list_empty(pages)))
			return;
		p = pages->next;
		bpage = list_entry(p, struct buffer_page, list);
		list_del_init(&bpage->list);
		list_add_tail(&bpage->list, &cpu_buffer->pages);
	}
	rb_reset_cpu(cpu_buffer);

	rb_check_pages(cpu_buffer);

	atomic_dec(&cpu_buffer->record_disabled);
}

/**
 * ring_buffer_resize - resize the ring buffer
 * @buffer: the buffer to resize.
 * @size: the new size.
 *
 * The tracer is responsible for making sure that the buffer is
 * not being used while changing the size.
 * Note: We may be able to change the above requirement by using
 *  RCU synchronizations.
 *
 * Minimum size is 2 * BUF_PAGE_SIZE.
 *
 * Returns -1 on failure.
 */
int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size)
{
	struct ring_buffer_per_cpu *cpu_buffer;
	unsigned nr_pages, rm_pages, new_pages;
	struct buffer_page *bpage, *tmp;
	unsigned long buffer_size;
	unsigned long addr;
	LIST_HEAD(pages);
	int i, cpu;

	/*
	 * Always succeed at resizing a non-existent buffer:
	 */
	if (!buffer)
		return size;

	size = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
	size *= BUF_PAGE_SIZE;
	buffer_size = buffer->pages * BUF_PAGE_SIZE;

	/* we need a minimum of two pages */
	if (size < BUF_PAGE_SIZE * 2)
		size = BUF_PAGE_SIZE * 2;

	if (size == buffer_size)
		return size;

	mutex_lock(&buffer->mutex);
	get_online_cpus();

	nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);

	if (size < buffer_size) {

		/* easy case, just free pages */
		if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
			goto out_fail;

		rm_pages = buffer->pages - nr_pages;

		for_each_buffer_cpu(buffer, cpu) {
			cpu_buffer = buffer->buffers[cpu];
			rb_remove_pages(cpu_buffer, rm_pages);
		}
		goto out;
	}

	/*
	 * This is a bit more difficult. We only want to add pages
	 * when we can allocate enough for all CPUs. We do this
	 * by allocating all the pages and storing them on a local
	 * link list. If we succeed in our allocation, then we
	 * add these pages to the cpu_buffers. Otherwise we just free
	 * them all and return -ENOMEM;
	 */
	if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
		goto out_fail;

	new_pages = nr_pages - buffer->pages;

	for_each_buffer_cpu(buffer, cpu) {
		for (i = 0; i < new_pages; i++) {
			bpage = kzalloc_node(ALIGN(sizeof(*bpage),
						  cache_line_size()),
					    GFP_KERNEL, cpu_to_node(cpu));
			if (!bpage)
				goto free_pages;
			list_add(&bpage->list, &pages);
			addr = __get_free_page(GFP_KERNEL);
			if (!addr)
				goto free_pages;
			bpage->page = (void *)addr;
			rb_init_page(bpage->page);
		}
	}

	for_each_buffer_cpu(buffer, cpu) {
		cpu_buffer = buffer->buffers[cpu];
		rb_insert_pages(cpu_buffer, &pages, new_pages);
	}

	if (RB_WARN_ON(buffer, !list_empty(&pages)))
		goto out_fail;

 out:
	buffer->pages = nr_pages;
	put_online_cpus();
	mutex_unlock(&buffer->mutex);

	return size;

 free_pages:
	list_for_each_entry_safe(bpage, tmp, &pages, list) {
		list_del_init(&bpage->list);
		free_buffer_page(bpage);
	}
	put_online_cpus();
	mutex_unlock(&buffer->mutex);
	return -ENOMEM;

	/*
	 * Something went totally wrong, and we are too paranoid
	 * to even clean up the mess.
	 */
 out_fail:
	put_online_cpus();
	mutex_unlock(&buffer->mutex);
	return -1;
}
EXPORT_SYMBOL_GPL(ring_buffer_resize);

static inline void *
__rb_data_page_index(struct buffer_data_page *bpage, unsigned index)
{
	return bpage->data + index;
}

static inline void *__rb_page_index(struct buffer_page *bpage, unsigned index)
{
	return bpage->page->data + index;
}

static 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 inline struct ring_buffer_event *
rb_head_event(struct ring_buffer_per_cpu *cpu_buffer)
{
	return __rb_page_index(cpu_buffer->head_page,
			       cpu_buffer->head_page->read);
}

static inline struct ring_buffer_event *
rb_iter_head_event(struct ring_buffer_iter *iter)
{
	return __rb_page_index(iter->head_page, iter->head);
}

static inline unsigned rb_page_write(struct buffer_page *bpage)
{
	return local_read(&bpage->write);
}

static inline unsigned rb_page_commit(struct buffer_page *bpage)
{
	return local_read(&bpage->page->commit);
}

/* Size is determined by what has been commited */
static inline unsigned rb_page_size(struct buffer_page *bpage)
{
	return rb_page_commit(bpage);
}

static inline unsigned
rb_commit_index(struct ring_buffer_per_cpu *cpu_buffer)
{
	return rb_page_commit(cpu_buffer->commit_page);
}

static inline unsigned rb_head_size(struct ring_buffer_per_cpu *cpu_buffer)
{
	return rb_page_commit(cpu_buffer->head_page);
}

/*
 * When the tail hits the head and the buffer is in overwrite mode,
 * the head jumps to the next page and all content on the previous
 * page is discarded. But before doing so, we update the overrun
 * variable of the buffer.
 */
static void rb_update_overflow(struct ring_buffer_per_cpu *cpu_buffer)
{
	struct ring_buffer_event *event;
	unsigned long head;

	for (head = 0; head < rb_head_size(cpu_buffer);
	     head += rb_event_length(event)) {

		event = __rb_page_index(cpu_buffer->head_page, head);
		if (RB_WARN_ON(cpu_buffer, rb_null_event(event)))
			return;
		/* Only count data entries */
		if (event->type != RINGBUF_TYPE_DATA)
			continue;
		cpu_buffer->overrun++;
		cpu_buffer->entries--;
	}
}

static inline void rb_inc_page(struct ring_buffer_per_cpu *cpu_buffer,
			       struct buffer_page **bpage)
{
	struct list_head *p = (*bpage)->list.next;

	if (p == &cpu_buffer->pages)
		p = p->next;

	*bpage = list_entry(p, struct buffer_page, list);
}

static inline unsigned
rb_event_index(struct ring_buffer_event *event)
{
	unsigned long addr = (unsigned long)event;

	return (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
}

static int
rb_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 void
rb_set_commit_event(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;

	while (cpu_buffer->commit_page->page != (void *)addr) {
		if (RB_WARN_ON(cpu_buffer,
			  cpu_buffer->commit_page == cpu_buffer->tail_page))
			return;
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
		cpu_buffer->write_stamp =
			cpu_buffer->commit_page->page->time_stamp;
	}

	/* Now set the commit to the event's index */
	local_set(&cpu_buffer->commit_page->page->commit, index);
}

static void
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
{
	/*
	 * 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:
	while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		rb_inc_page(cpu_buffer, &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)) {
		cpu_buffer->commit_page->page->commit =
			cpu_buffer->commit_page->write;
		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 != cpu_buffer->tail_page))
		goto again;
}

static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
	cpu_buffer->read_stamp = cpu_buffer->reader_page->page->time_stamp;
	cpu_buffer->reader_page->read = 0;
}

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 = cpu_buffer->head_page;
	else
		rb_inc_page(cpu_buffer, &iter->head_page);

	iter->read_stamp = iter->head_page->page->time_stamp;
	iter->head = 0;
}

/**
 * ring_buffer_update_event - update event type and data
 * @event: the even 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_event *event,
			 unsigned type, unsigned length)
{
	event->type = type;

	switch (type) {

	case RINGBUF_TYPE_PADDING:
		break;

	case RINGBUF_TYPE_TIME_EXTEND:
		event->len = DIV_ROUND_UP(RB_LEN_TIME_EXTEND, RB_ALIGNMENT);
		break;

	case RINGBUF_TYPE_TIME_STAMP:
		event->len = DIV_ROUND_UP(RB_LEN_TIME_STAMP, RB_ALIGNMENT);
		break;

	case RINGBUF_TYPE_DATA:
		length -= RB_EVNT_HDR_SIZE;
		if (length > RB_MAX_SMALL_DATA) {
			event->len = 0;
			event->array[0] = length;
		} else
			event->len = DIV_ROUND_UP(length, RB_ALIGNMENT);
		break;
	default:
		BUG();
	}
}

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 = 1;

	if (length > RB_MAX_SMALL_DATA)
		length += sizeof(event.array[0]);

	length += RB_EVNT_HDR_SIZE;
	length = ALIGN(length, RB_ALIGNMENT);

	return length;
}

static struct ring_buffer_event *
__rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
		  unsigned type, unsigned long length, u64 *ts)
{
	struct buffer_page *tail_page, *head_page, *reader_page, *commit_page;
	unsigned long tail, write;
	struct ring_buffer *buffer = cpu_buffer->buffer;
	struct ring_buffer_event *event;
	unsigned long flags;
	bool lock_taken = false;

	commit_page = cpu_buffer->commit_page;
	/* we just need to protect against interrupts */
	barrier();
	tail_page = cpu_buffer->tail_page;
	write = local_add_return(length, &tail_page->write);
	tail = write - length;

	/* See if we shot pass the end of this buffer page */
	if (write > BUF_PAGE_SIZE) {
		struct buffer_page *next_page = tail_page;

		local_irq_save(flags);
		/*
		 * Since the write to the buffer is still not
		 * fully lockless, we must be careful with NMIs.
		 * The locks in the writers are taken when a write
		 * crosses to a new page. The locks protect against
		 * races with the readers (this will soon be fixed
		 * with a lockless solution).
		 *
		 * Because we can not protect against NMIs, and we
		 * want to keep traces reentrant, we need to manage
		 * what happens when we are in an NMI.
		 *
		 * NMIs can happen after we take the lock.
		 * If we are in an NMI, only take the lock
		 * if it is not already taken. Otherwise
		 * simply fail.
		 */
		if (unlikely(in_nmi())) {
			if (!__raw_spin_trylock(&cpu_buffer->lock))
				goto out_reset;
		} else
			__raw_spin_lock(&cpu_buffer->lock);

		lock_taken = true;

		rb_inc_page(cpu_buffer, &next_page);

		head_page = cpu_buffer->head_page;
		reader_page = cpu_buffer->reader_page;

		/* we grabbed the lock before incrementing */
		if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
			goto out_reset;

		/*
		 * 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)) {
			WARN_ON_ONCE(1);
			goto out_reset;
		}

		if (next_page == head_page) {
			if (!(buffer->flags & RB_FL_OVERWRITE))
				goto out_reset;

			/* tail_page has not moved yet? */
			if (tail_page == cpu_buffer->tail_page) {
				/* count overflows */
				rb_update_overflow(cpu_buffer);

				rb_inc_page(cpu_buffer, &head_page);
				cpu_buffer->head_page = head_page;
				cpu_buffer->head_page->read = 0;
			}
		}

		/*
		 * 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 == cpu_buffer->tail_page) {
			local_set(&next_page->write, 0);
			local_set(&next_page->page->commit, 0);
			cpu_buffer->tail_page = next_page;

			/* reread the time stamp */
			*ts = ring_buffer_time_stamp(buffer, cpu_buffer->cpu);
			cpu_buffer->tail_page->page->time_stamp = *ts;
		}

		/*
		 * The actual tail page has moved forward.
		 */
		if (tail < BUF_PAGE_SIZE) {
			/* Mark the rest of the page with padding */
			event = __rb_page_index(tail_page, tail);
			rb_event_set_padding(event);
		}

		if (tail <= BUF_PAGE_SIZE)
			/* Set the write back to the previous setting */
			local_set(&tail_page->write, tail);

		/*
		 * If this was a commit entry that failed,
		 * increment that too
		 */
		if (tail_page == cpu_buffer->commit_page &&
		    tail == rb_commit_index(cpu_buffer)) {
			rb_set_commit_to_write(cpu_buffer);
		}

		__raw_spin_unlock(&cpu_buffer->lock);
		local_irq_restore(flags);

		/* fail and let the caller try again */
		return ERR_PTR(-EAGAIN);
	}

	/* We reserved something on the buffer */

	if (RB_WARN_ON(cpu_buffer, write > BUF_PAGE_SIZE))
		return NULL;

	event = __rb_page_index(tail_page, tail);
	rb_update_event(event, type, length);

	/*
	 * If this is a commit and the tail is zero, then update
	 * this page's time stamp.
	 */
	if (!tail && rb_is_commit(cpu_buffer, event))
		cpu_buffer->commit_page->page->time_stamp = *ts;

	return event;

 out_reset:
	/* reset write */
	if (tail <= BUF_PAGE_SIZE)
		local_set(&tail_page->write, tail);

	if (likely(lock_taken))
		__raw_spin_unlock(&cpu_buffer->lock);
	local_irq_restore(flags);
	return NULL;
}

static int
rb_add_time_stamp(struct ring_buffer_per_cpu *cpu_buffer,
		  u64 *ts, u64 *delta)
{
	struct ring_buffer_event *event;
	static int once;
	int ret;

	if (unlikely(*delta > (1ULL << 59) && !once++)) {
		printk(KERN_WARNING "Delta way too big! %llu"
		       " ts=%llu write stamp = %llu\n",
		       (unsigned long long)*delta,
		       (unsigned long long)*ts,
		       (unsigned long long)cpu_buffer->write_stamp);
		WARN_ON(1);
	}

	/*
	 * The delta is too big, we to add a
	 * new timestamp.
	 */
	event = __rb_reserve_next(cpu_buffer,
				  RINGBUF_TYPE_TIME_EXTEND,
				  RB_LEN_TIME_EXTEND,
				  ts);
	if (!event)
		return -EBUSY;

	if (PTR_ERR(event) == -EAGAIN)
		return -EAGAIN;

	/* Only a commited time event can update the write stamp */
	if (rb_is_commit(cpu_buffer, event)) {
		/*
		 * If this is the first on the page, then we need to
		 * update the page itself, and just put in a zero.
		 */
		if (rb_event_index(event)) {
			event->time_delta = *delta & TS_MASK;
			event->array[0] = *delta >> TS_SHIFT;
		} else {
			cpu_buffer->commit_page->page->time_stamp = *ts;
			event->time_delta = 0;
			event->array[0] = 0;
		}
		cpu_buffer->write_stamp = *ts;
		/* let the caller know this was the commit */
		ret = 1;
	} else {
		/* Darn, this is just wasted space */
		event->time_delta = 0;
		event->array[0] = 0;
		ret = 0;
	}

	*delta = 0;

	return ret;
}

static struct ring_buffer_event *
rb_reserve_next_event(struct ring_buffer_per_cpu *cpu_buffer,
		      unsigned type, unsigned long length)
{
	struct ring_buffer_event *event;
	u64 ts, delta;
	int commit = 0;
	int nr_loops = 0;

 again:
	/*
	 * 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))
		return NULL;

	ts = ring_buffer_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);

	/*
	 * Only the first commit can update the timestamp.
	 * Yes there is a race here. If an interrupt comes in
	 * just after the conditional and it traces too, then it
	 * will also check the deltas. More than one timestamp may
	 * also be made. But only the entry that did the actual
	 * commit will be something other than zero.
	 */
	if (cpu_buffer->tail_page == cpu_buffer->commit_page &&
	    rb_page_write(cpu_buffer->tail_page) ==
	    rb_commit_index(cpu_buffer)) {

		delta = ts - cpu_buffer->write_stamp;

		/* make sure this delta is calculated here */
		barrier();

		/* Did the write stamp get updated already? */
		if (unlikely(ts < cpu_buffer->write_stamp))
			delta = 0;

		if (test_time_stamp(delta)) {

			commit = rb_add_time_stamp(cpu_buffer, &ts, &delta);

			if (commit == -EBUSY)
				return NULL;

			if (commit == -EAGAIN)
				goto again;

			RB_WARN_ON(cpu_buffer, commit < 0);
		}
	} else
		/* Non commits have zero deltas */
		delta = 0;

	event = __rb_reserve_next(cpu_buffer, type, length, &ts);
	if (PTR_ERR(event) == -EAGAIN)
		goto again;

	if (!event) {
		if (unlikely(commit))
			/*
			 * Ouch! We needed a timestamp and it was commited. But
			 * we didn't get our event reserved.
			 */
			rb_set_commit_to_write(cpu_buffer);
		return NULL;
	}

	/*
	 * If the timestamp was commited, make the commit our entry
	 * now so that we will update it when needed.
	 */
	if (commit)
		rb_set_commit_event(cpu_buffer, event);
	else if (!rb_is_commit(cpu_buffer, event))
		delta = 0;

	event->time_delta = delta;

	return event;
}

static int trace_irq_level(void)
{
	return hardirq_count() + softirq_count() + in_nmi();
}

static int trace_recursive_lock(void)
{
	int level;

	level = trace_irq_level();

	if (unlikely(current->trace_recursion & (1 << level))) {
		/* Disable all tracing before we do anything else */
		tracing_off_permanent();

		printk_once(KERN_WARNING "Tracing recursion: "
			    "HC[%lu]:SC[%lu]:NMI[%lu]\n",
			    hardirq_count() >> HARDIRQ_SHIFT,
			    softirq_count() >> SOFTIRQ_SHIFT,
			    in_nmi());

		WARN_ON_ONCE(1);
		return -1;
	}

	current->trace_recursion |= 1 << level;

	return 0;
}

static void trace_recursive_unlock(void)
{
	int level;

	level = trace_irq_level();

	WARN_ON_ONCE(!current->trace_recursion & (1 << level));

	current->trace_recursion &= ~(1 << level);
}

static DEFINE_PER_CPU(int, rb_need_resched);

/**
{'fraction_non_alphanumeric': 0.11750637129974514, 'fraction_numerical': 0.003816245180683526, 'mean_word_length': 3.5790544584081387, 'pattern_counts': {'":': 0, '<': 105, '<?xml version=': 0, '>': 587, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 12, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '90023', 'n_tokens_mistral': 28581, 'n_tokens_neox': 26550, 'n_words': 7136}