linux/kernel/trace/ring_buffer.c

2187 lines
52 KiB
C

/*
* Generic ring buffer
*
* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#include <linux/ring_buffer.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <linux/uaccess.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/mutex.h>
#include <linux/sched.h> /* used for sched_clock() (for now) */
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/list.h>
#include <linux/fs.h>
#include "trace.h"
/* Global flag to disable all recording to ring buffers */
static int ring_buffers_off __read_mostly;
/**
* tracing_on - enable all tracing buffers
*
* This function enables all tracing buffers that may have been
* disabled with tracing_off.
*/
void tracing_on(void)
{
ring_buffers_off = 0;
}
/**
* 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)
{
ring_buffers_off = 1;
}
/* Up this if you want to test the TIME_EXTENTS and normalization */
#define DEBUG_SHIFT 0
/* FIXME!!! */
u64 ring_buffer_time_stamp(int cpu)
{
u64 time;
preempt_disable_notrace();
/* shift to debug/test normalization and TIME_EXTENTS */
time = sched_clock() << DEBUG_SHIFT;
preempt_enable_notrace();
return time;
}
void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
{
/* Just stupid testing the normalize function and deltas */
*ts >>= DEBUG_SHIFT;
}
#define RB_EVNT_HDR_SIZE (sizeof(struct ring_buffer_event))
#define RB_ALIGNMENT_SHIFT 2
#define RB_ALIGNMENT (1 << RB_ALIGNMENT_SHIFT)
#define RB_MAX_SMALL_DATA 28
enum {
RB_LEN_TIME_EXTEND = 8,
RB_LEN_TIME_STAMP = 16,
};
/* inline for ring buffer fast paths */
static inline unsigned
rb_event_length(struct ring_buffer_event *event)
{
unsigned length;
switch (event->type) {
case RINGBUF_TYPE_PADDING:
/* undefined */
return -1;
case RINGBUF_TYPE_TIME_EXTEND:
return RB_LEN_TIME_EXTEND;
case RINGBUF_TYPE_TIME_STAMP:
return RB_LEN_TIME_STAMP;
case RINGBUF_TYPE_DATA:
if (event->len)
length = event->len << RB_ALIGNMENT_SHIFT;
else
length = event->array[0];
return length + RB_EVNT_HDR_SIZE;
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)
{
return rb_event_length(event);
}
/* inline for ring buffer fast paths */
static inline 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);
}
#define for_each_buffer_cpu(buffer, cpu) \
for_each_cpu_mask(cpu, buffer->cpumask)
#define TS_SHIFT 27
#define TS_MASK ((1ULL << TS_SHIFT) - 1)
#define TS_DELTA_TEST (~TS_MASK)
/*
* This hack stolen from mm/slob.c.
* We can store per page timing information in the page frame of the page.
* Thanks to Peter Zijlstra for suggesting this idea.
*/
struct buffer_page {
u64 time_stamp; /* page time stamp */
local_t write; /* index for next write */
local_t commit; /* write commited index */
unsigned read; /* index for next read */
struct list_head list; /* list of free pages */
void *page; /* Actual data page */
};
/*
* Also stolen from mm/slob.c. Thanks to Mathieu Desnoyers for pointing
* this issue out.
*/
static inline void free_buffer_page(struct buffer_page *bpage)
{
if (bpage->page)
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
/*
* head_page == tail_page && head == tail then buffer is empty.
*/
struct ring_buffer_per_cpu {
int cpu;
struct ring_buffer *buffer;
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; /* commited 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 long size;
unsigned pages;
unsigned flags;
int cpus;
cpumask_t cpumask;
atomic_t record_disabled;
struct mutex mutex;
struct ring_buffer_per_cpu **buffers;
};
struct ring_buffer_iter {
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long head;
struct buffer_page *head_page;
u64 read_stamp;
};
#define RB_WARN_ON(buffer, cond) \
do { \
if (unlikely(cond)) { \
atomic_inc(&buffer->record_disabled); \
WARN_ON(1); \
} \
} while (0)
#define RB_WARN_ON_RET(buffer, cond) \
do { \
if (unlikely(cond)) { \
atomic_inc(&buffer->record_disabled); \
WARN_ON(1); \
return -1; \
} \
} while (0)
#define RB_WARN_ON_ONCE(buffer, cond) \
do { \
static int once; \
if (unlikely(cond) && !once) { \
once++; \
atomic_inc(&buffer->record_disabled); \
WARN_ON(1); \
} \
} while (0)
/**
* check_pages - integrity check of buffer pages
* @cpu_buffer: CPU buffer with pages to test
*
* As a safty 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 *page, *tmp;
RB_WARN_ON_RET(cpu_buffer, head->next->prev != head);
RB_WARN_ON_RET(cpu_buffer, head->prev->next != head);
list_for_each_entry_safe(page, tmp, head, list) {
RB_WARN_ON_RET(cpu_buffer,
page->list.next->prev != &page->list);
RB_WARN_ON_RET(cpu_buffer,
page->list.prev->next != &page->list);
}
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 *page, *tmp;
unsigned long addr;
LIST_HEAD(pages);
unsigned i;
for (i = 0; i < nr_pages; i++) {
page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
if (!page)
goto free_pages;
list_add(&page->list, &pages);
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
page->page = (void *)addr;
}
list_splice(&pages, head);
rb_check_pages(cpu_buffer);
return 0;
free_pages:
list_for_each_entry_safe(page, tmp, &pages, list) {
list_del_init(&page->list);
free_buffer_page(page);
}
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 *page;
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->lock);
INIT_LIST_HEAD(&cpu_buffer->pages);
page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
if (!page)
goto fail_free_buffer;
cpu_buffer->reader_page = page;
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto fail_free_reader;
page->page = (void *)addr;
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 *page, *tmp;
list_del_init(&cpu_buffer->reader_page->list);
free_buffer_page(cpu_buffer->reader_page);
list_for_each_entry_safe(page, tmp, head, list) {
list_del_init(&page->list);
free_buffer_page(page);
}
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);
/**
* ring_buffer_alloc - allocate a new ring_buffer
* @size: the size in bytes 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;
buffer->pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
buffer->flags = flags;
/* need at least two pages */
if (buffer->pages == 1)
buffer->pages++;
buffer->cpumask = cpu_possible_map;
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_buffer;
for_each_buffer_cpu(buffer, cpu) {
buffer->buffers[cpu] =
rb_allocate_cpu_buffer(buffer, cpu);
if (!buffer->buffers[cpu])
goto fail_free_buffers;
}
mutex_init(&buffer->mutex);
return buffer;
fail_free_buffers:
for_each_buffer_cpu(buffer, cpu) {
if (buffer->buffers[cpu])
rb_free_cpu_buffer(buffer->buffers[cpu]);
}
kfree(buffer->buffers);
fail_free_buffer:
kfree(buffer);
return NULL;
}
/**
* ring_buffer_free - free a ring buffer.
* @buffer: the buffer to free.
*/
void
ring_buffer_free(struct ring_buffer *buffer)
{
int cpu;
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
kfree(buffer);
}
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 *page;
struct list_head *p;
unsigned i;
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
for (i = 0; i < nr_pages; i++) {
BUG_ON(list_empty(&cpu_buffer->pages));
p = cpu_buffer->pages.next;
page = list_entry(p, struct buffer_page, list);
list_del_init(&page->list);
free_buffer_page(page);
}
BUG_ON(list_empty(&cpu_buffer->pages));
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 *page;
struct list_head *p;
unsigned i;
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
for (i = 0; i < nr_pages; i++) {
BUG_ON(list_empty(pages));
p = pages->next;
page = list_entry(p, struct buffer_page, list);
list_del_init(&page->list);
list_add_tail(&page->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 *page, *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);
nr_pages = DIV_ROUND_UP(size, BUF_PAGE_SIZE);
if (size < buffer_size) {
/* easy case, just free pages */
BUG_ON(nr_pages >= buffer->pages);
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;
*/
BUG_ON(nr_pages <= buffer->pages);
new_pages = nr_pages - buffer->pages;
for_each_buffer_cpu(buffer, cpu) {
for (i = 0; i < new_pages; i++) {
page = kzalloc_node(ALIGN(sizeof(*page),
cache_line_size()),
GFP_KERNEL, cpu_to_node(cpu));
if (!page)
goto free_pages;
list_add(&page->list, &pages);
addr = __get_free_page(GFP_KERNEL);
if (!addr)
goto free_pages;
page->page = (void *)addr;
}
}
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
rb_insert_pages(cpu_buffer, &pages, new_pages);
}
BUG_ON(!list_empty(&pages));
out:
buffer->pages = nr_pages;
mutex_unlock(&buffer->mutex);
return size;
free_pages:
list_for_each_entry_safe(page, tmp, &pages, list) {
list_del_init(&page->list);
free_buffer_page(page);
}
mutex_unlock(&buffer->mutex);
return -ENOMEM;
}
static inline int rb_null_event(struct ring_buffer_event *event)
{
return event->type == RINGBUF_TYPE_PADDING;
}
static inline void *__rb_page_index(struct buffer_page *page, unsigned index)
{
return page->page + 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->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);
BUG_ON(rb_null_event(event));
/* 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 **page)
{
struct list_head *p = (*page)->list.next;
if (p == &cpu_buffer->pages)
p = p->next;
*page = 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 inline 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 inline 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) {
RB_WARN_ON(cpu_buffer,
cpu_buffer->commit_page == cpu_buffer->tail_page);
cpu_buffer->commit_page->commit =
cpu_buffer->commit_page->write;
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
cpu_buffer->write_stamp = cpu_buffer->commit_page->time_stamp;
}
/* Now set the commit to the event's index */
local_set(&cpu_buffer->commit_page->commit, index);
}
static inline 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.
*/
while (cpu_buffer->commit_page != cpu_buffer->tail_page) {
cpu_buffer->commit_page->commit =
cpu_buffer->commit_page->write;
rb_inc_page(cpu_buffer, &cpu_buffer->commit_page);
cpu_buffer->write_stamp = cpu_buffer->commit_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->commit =
cpu_buffer->commit_page->write;
barrier();
}
}
static void rb_reset_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
cpu_buffer->read_stamp = cpu_buffer->reader_page->time_stamp;
cpu_buffer->reader_page->read = 0;
}
static inline 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->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 inline 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 =
(RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
>> RB_ALIGNMENT_SHIFT;
break;
case RINGBUF_TYPE_TIME_STAMP:
event->len =
(RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
>> RB_ALIGNMENT_SHIFT;
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 =
(length + (RB_ALIGNMENT-1))
>> RB_ALIGNMENT_SHIFT;
break;
default:
BUG();
}
}
static inline 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;
unsigned long tail, write;
struct ring_buffer *buffer = cpu_buffer->buffer;
struct ring_buffer_event *event;
unsigned long flags;
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;
spin_lock_irqsave(&cpu_buffer->lock, flags);
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 */
RB_WARN_ON(cpu_buffer, next_page == reader_page);
/*
* If for some reason, we had an interrupt storm that made
* it all the way around the buffer, bail, and warn
* about it.
*/
if (unlikely(next_page == cpu_buffer->commit_page)) {
WARN_ON_ONCE(1);
goto out_unlock;
}
if (next_page == head_page) {
if (!(buffer->flags & RB_FL_OVERWRITE)) {
/* reset write */
if (tail <= BUF_PAGE_SIZE)
local_set(&tail_page->write, tail);
goto out_unlock;
}
/* 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->commit, 0);
cpu_buffer->tail_page = next_page;
/* reread the time stamp */
*ts = ring_buffer_time_stamp(cpu_buffer->cpu);
cpu_buffer->tail_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);
event->type = RINGBUF_TYPE_PADDING;
}
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);
}
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
/* fail and let the caller try again */
return ERR_PTR(-EAGAIN);
}
/* We reserved something on the buffer */
BUG_ON(write > BUF_PAGE_SIZE);
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->time_stamp = *ts;
return event;
out_unlock:
spin_unlock_irqrestore(&cpu_buffer->lock, 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->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 (unlikely(++nr_loops > 1000)) {
RB_WARN_ON(cpu_buffer, 1);
return NULL;
}
ts = ring_buffer_time_stamp(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 DEFINE_PER_CPU(int, rb_need_resched);
/**
* ring_buffer_lock_reserve - reserve a part of the buffer
* @buffer: the ring buffer to reserve from
* @length: the length of the data to reserve (excluding event header)
* @flags: a pointer to save the interrupt flags
*
* Returns a reseverd event on the ring buffer to copy directly to.
* The user of this interface will need to get the body to write into
* and can use the ring_buffer_event_data() interface.
*
* The length is the length of the data needed, not the event length
* which also includes the event header.
*
* Must be paired with ring_buffer_unlock_commit, unless NULL is returned.
* If NULL is returned, then nothing has been allocated or locked.
*/
struct ring_buffer_event *
ring_buffer_lock_reserve(struct ring_buffer *buffer,
unsigned long length,
unsigned long *flags)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
int cpu, resched;
if (ring_buffers_off)
return NULL;
if (atomic_read(&buffer->record_disabled))
return NULL;
/* If we are tracing schedule, we don't want to recurse */
resched = need_resched();
preempt_disable_notrace();
cpu = raw_smp_processor_id();
if (!cpu_isset(cpu, buffer->cpumask))
goto out;
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled))
goto out;
length = rb_calculate_event_length(length);
if (length > BUF_PAGE_SIZE)
goto out;
event = rb_reserve_next_event(cpu_buffer, RINGBUF_TYPE_DATA, length);
if (!event)
goto out;
/*
* Need to store resched state on this cpu.
* Only the first needs to.
*/
if (preempt_count() == 1)
per_cpu(rb_need_resched, cpu) = resched;
return event;
out:
if (resched)
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
return NULL;
}
static void rb_commit(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
cpu_buffer->entries++;
/* Only process further if we own the commit */
if (!rb_is_commit(cpu_buffer, event))
return;
cpu_buffer->write_stamp += event->time_delta;
rb_set_commit_to_write(cpu_buffer);
}
/**
* ring_buffer_unlock_commit - commit a reserved
* @buffer: The buffer to commit to
* @event: The event pointer to commit.
* @flags: the interrupt flags received from ring_buffer_lock_reserve.
*
* This commits the data to the ring buffer, and releases any locks held.
*
* Must be paired with ring_buffer_lock_reserve.
*/
int ring_buffer_unlock_commit(struct ring_buffer *buffer,
struct ring_buffer_event *event,
unsigned long flags)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu = raw_smp_processor_id();
cpu_buffer = buffer->buffers[cpu];
rb_commit(cpu_buffer, event);
/*
* Only the last preempt count needs to restore preemption.
*/
if (preempt_count() == 1) {
if (per_cpu(rb_need_resched, cpu))
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
} else
preempt_enable_no_resched_notrace();
return 0;
}
/**
* ring_buffer_write - write data to the buffer without reserving
* @buffer: The ring buffer to write to.
* @length: The length of the data being written (excluding the event header)
* @data: The data to write to the buffer.
*
* This is like ring_buffer_lock_reserve and ring_buffer_unlock_commit as
* one function. If you already have the data to write to the buffer, it
* may be easier to simply call this function.
*
* Note, like ring_buffer_lock_reserve, the length is the length of the data
* and not the length of the event which would hold the header.
*/
int ring_buffer_write(struct ring_buffer *buffer,
unsigned long length,
void *data)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
unsigned long event_length;
void *body;
int ret = -EBUSY;
int cpu, resched;
if (ring_buffers_off)
return -EBUSY;
if (atomic_read(&buffer->record_disabled))
return -EBUSY;
resched = need_resched();
preempt_disable_notrace();
cpu = raw_smp_processor_id();
if (!cpu_isset(cpu, buffer->cpumask))
goto out;
cpu_buffer = buffer->buffers[cpu];
if (atomic_read(&cpu_buffer->record_disabled))
goto out;
event_length = rb_calculate_event_length(length);
event = rb_reserve_next_event(cpu_buffer,
RINGBUF_TYPE_DATA, event_length);
if (!event)
goto out;
body = rb_event_data(event);
memcpy(body, data, length);
rb_commit(cpu_buffer, event);
ret = 0;
out:
if (resched)
preempt_enable_no_resched_notrace();
else
preempt_enable_notrace();
return ret;
}
static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = cpu_buffer->reader_page;
struct buffer_page *head = cpu_buffer->head_page;
struct buffer_page *commit = cpu_buffer->commit_page;
return reader->read == rb_page_commit(reader) &&
(commit == reader ||
(commit == head &&
head->read == rb_page_commit(commit)));
}
/**
* ring_buffer_record_disable - stop all writes into the buffer
* @buffer: The ring buffer to stop writes to.
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_sched() after this.
*/
void ring_buffer_record_disable(struct ring_buffer *buffer)
{
atomic_inc(&buffer->record_disabled);
}
/**
* ring_buffer_record_enable - enable writes to the buffer
* @buffer: The ring buffer to enable writes
*
* Note, multiple disables will need the same number of enables
* to truely enable the writing (much like preempt_disable).
*/
void ring_buffer_record_enable(struct ring_buffer *buffer)
{
atomic_dec(&buffer->record_disabled);
}
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
* @cpu: The CPU buffer to stop
*
* This prevents all writes to the buffer. Any attempt to write
* to the buffer after this will fail and return NULL.
*
* The caller should call synchronize_sched() after this.
*/
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpu_isset(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_inc(&cpu_buffer->record_disabled);
}
/**
* ring_buffer_record_enable_cpu - enable writes to the buffer
* @buffer: The ring buffer to enable writes
* @cpu: The CPU to enable.
*
* Note, multiple disables will need the same number of enables
* to truely enable the writing (much like preempt_disable).
*/
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpu_isset(cpu, buffer->cpumask))
return;
cpu_buffer = buffer->buffers[cpu];
atomic_dec(&cpu_buffer->record_disabled);
}
/**
* ring_buffer_entries_cpu - get the number of entries in a cpu buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the entries from.
*/
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpu_isset(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
return cpu_buffer->entries;
}
/**
* ring_buffer_overrun_cpu - get the number of overruns in a cpu_buffer
* @buffer: The ring buffer
* @cpu: The per CPU buffer to get the number of overruns from
*/
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpu_isset(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
return cpu_buffer->overrun;
}
/**
* ring_buffer_entries - get the number of entries in a buffer
* @buffer: The ring buffer
*
* Returns the total number of entries in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_entries(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long entries = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
entries += cpu_buffer->entries;
}
return entries;
}
/**
* ring_buffer_overrun_cpu - get the number of overruns in buffer
* @buffer: The ring buffer
*
* Returns the total number of overruns in the ring buffer
* (all CPU entries)
*/
unsigned long ring_buffer_overruns(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
unsigned long overruns = 0;
int cpu;
/* if you care about this being correct, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
overruns += cpu_buffer->overrun;
}
return overruns;
}
/**
* ring_buffer_iter_reset - reset an iterator
* @iter: The iterator to reset
*
* Resets the iterator, so that it will start from the beginning
* again.
*/
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
/* Iterator usage is expected to have record disabled */
if (list_empty(&cpu_buffer->reader_page->list)) {
iter->head_page = cpu_buffer->head_page;
iter->head = cpu_buffer->head_page->read;
} else {
iter->head_page = cpu_buffer->reader_page;
iter->head = cpu_buffer->reader_page->read;
}
if (iter->head)
iter->read_stamp = cpu_buffer->read_stamp;
else
iter->read_stamp = iter->head_page->time_stamp;
}
/**
* ring_buffer_iter_empty - check if an iterator has no more to read
* @iter: The iterator to check
*/
int ring_buffer_iter_empty(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer;
cpu_buffer = iter->cpu_buffer;
return iter->head_page == cpu_buffer->commit_page &&
iter->head == rb_commit_index(cpu_buffer);
}
static void
rb_update_read_stamp(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
u64 delta;
switch (event->type) {
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = event->array[0];
delta <<= TS_SHIFT;
delta += event->time_delta;
cpu_buffer->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
return;
case RINGBUF_TYPE_DATA:
cpu_buffer->read_stamp += event->time_delta;
return;
default:
BUG();
}
return;
}
static void
rb_update_iter_read_stamp(struct ring_buffer_iter *iter,
struct ring_buffer_event *event)
{
u64 delta;
switch (event->type) {
case RINGBUF_TYPE_PADDING:
return;
case RINGBUF_TYPE_TIME_EXTEND:
delta = event->array[0];
delta <<= TS_SHIFT;
delta += event->time_delta;
iter->read_stamp += delta;
return;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
return;
case RINGBUF_TYPE_DATA:
iter->read_stamp += event->time_delta;
return;
default:
BUG();
}
return;
}
static struct buffer_page *
rb_get_reader_page(struct ring_buffer_per_cpu *cpu_buffer)
{
struct buffer_page *reader = NULL;
unsigned long flags;
int nr_loops = 0;
spin_lock_irqsave(&cpu_buffer->lock, flags);
again:
/*
* This should normally only loop twice. But because the
* start of the reader inserts an empty page, it causes
* a case where we will loop three times. There should be no
* reason to loop four times (that I know of).
*/
if (unlikely(++nr_loops > 3)) {
RB_WARN_ON(cpu_buffer, 1);
reader = NULL;
goto out;
}
reader = cpu_buffer->reader_page;
/* If there's more to read, return this page */
if (cpu_buffer->reader_page->read < rb_page_size(reader))
goto out;
/* Never should we have an index greater than the size */
RB_WARN_ON(cpu_buffer,
cpu_buffer->reader_page->read > rb_page_size(reader));
/* check if we caught up to the tail */
reader = NULL;
if (cpu_buffer->commit_page == cpu_buffer->reader_page)
goto out;
/*
* Splice the empty reader page into the list around the head.
* Reset the reader page to size zero.
*/
reader = cpu_buffer->head_page;
cpu_buffer->reader_page->list.next = reader->list.next;
cpu_buffer->reader_page->list.prev = reader->list.prev;
local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->commit, 0);
/* Make the reader page now replace the head */
reader->list.prev->next = &cpu_buffer->reader_page->list;
reader->list.next->prev = &cpu_buffer->reader_page->list;
/*
* If the tail is on the reader, then we must set the head
* to the inserted page, otherwise we set it one before.
*/
cpu_buffer->head_page = cpu_buffer->reader_page;
if (cpu_buffer->commit_page != reader)
rb_inc_page(cpu_buffer, &cpu_buffer->head_page);
/* Finally update the reader page to the new head */
cpu_buffer->reader_page = reader;
rb_reset_reader_page(cpu_buffer);
goto again;
out:
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
return reader;
}
static void rb_advance_reader(struct ring_buffer_per_cpu *cpu_buffer)
{
struct ring_buffer_event *event;
struct buffer_page *reader;
unsigned length;
reader = rb_get_reader_page(cpu_buffer);
/* This function should not be called when buffer is empty */
BUG_ON(!reader);
event = rb_reader_event(cpu_buffer);
if (event->type == RINGBUF_TYPE_DATA)
cpu_buffer->entries--;
rb_update_read_stamp(cpu_buffer, event);
length = rb_event_length(event);
cpu_buffer->reader_page->read += length;
}
static void rb_advance_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
unsigned length;
cpu_buffer = iter->cpu_buffer;
buffer = cpu_buffer->buffer;
/*
* Check if we are at the end of the buffer.
*/
if (iter->head >= rb_page_size(iter->head_page)) {
BUG_ON(iter->head_page == cpu_buffer->commit_page);
rb_inc_iter(iter);
return;
}
event = rb_iter_head_event(iter);
length = rb_event_length(event);
/*
* This should not be called to advance the header if we are
* at the tail of the buffer.
*/
BUG_ON((iter->head_page == cpu_buffer->commit_page) &&
(iter->head + length > rb_commit_index(cpu_buffer)));
rb_update_iter_read_stamp(iter, event);
iter->head += length;
/* check for end of page padding */
if ((iter->head >= rb_page_size(iter->head_page)) &&
(iter->head_page != cpu_buffer->commit_page))
rb_advance_iter(iter);
}
/**
* ring_buffer_peek - peek at the next event to be read
* @buffer: The ring buffer to read
* @cpu: The cpu to peak at
* @ts: The timestamp counter of this event.
*
* This will return the event that will be read next, but does
* not consume the data.
*/
struct ring_buffer_event *
ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
struct buffer_page *reader;
int nr_loops = 0;
if (!cpu_isset(cpu, buffer->cpumask))
return NULL;
cpu_buffer = buffer->buffers[cpu];
again:
/*
* We repeat when a timestamp is encountered. It is possible
* to get multiple timestamps from an interrupt entering just
* as one timestamp is about to be written. The max times
* that this can happen is the number of nested interrupts we
* can have. Nesting 10 deep of interrupts is clearly
* an anomaly.
*/
if (unlikely(++nr_loops > 10)) {
RB_WARN_ON(cpu_buffer, 1);
return NULL;
}
reader = rb_get_reader_page(cpu_buffer);
if (!reader)
return NULL;
event = rb_reader_event(cpu_buffer);
switch (event->type) {
case RINGBUF_TYPE_PADDING:
RB_WARN_ON(cpu_buffer, 1);
rb_advance_reader(cpu_buffer);
return NULL;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
rb_advance_reader(cpu_buffer);
goto again;
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = cpu_buffer->read_stamp + event->time_delta;
ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
}
return event;
default:
BUG();
}
return NULL;
}
/**
* ring_buffer_iter_peek - peek at the next event to be read
* @iter: The ring buffer iterator
* @ts: The timestamp counter of this event.
*
* This will return the event that will be read next, but does
* not increment the iterator.
*/
struct ring_buffer_event *
ring_buffer_iter_peek(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer *buffer;
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
int nr_loops = 0;
if (ring_buffer_iter_empty(iter))
return NULL;
cpu_buffer = iter->cpu_buffer;
buffer = cpu_buffer->buffer;
again:
/*
* We repeat when a timestamp is encountered. It is possible
* to get multiple timestamps from an interrupt entering just
* as one timestamp is about to be written. The max times
* that this can happen is the number of nested interrupts we
* can have. Nesting 10 deep of interrupts is clearly
* an anomaly.
*/
if (unlikely(++nr_loops > 10)) {
RB_WARN_ON(cpu_buffer, 1);
return NULL;
}
if (rb_per_cpu_empty(cpu_buffer))
return NULL;
event = rb_iter_head_event(iter);
switch (event->type) {
case RINGBUF_TYPE_PADDING:
rb_inc_iter(iter);
goto again;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_TIME_STAMP:
/* FIXME: not implemented */
rb_advance_iter(iter);
goto again;
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = iter->read_stamp + event->time_delta;
ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
}
return event;
default:
BUG();
}
return NULL;
}
/**
* ring_buffer_consume - return an event and consume it
* @buffer: The ring buffer to get the next event from
*
* Returns the next event in the ring buffer, and that event is consumed.
* Meaning, that sequential reads will keep returning a different event,
* and eventually empty the ring buffer if the producer is slower.
*/
struct ring_buffer_event *
ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
if (!cpu_isset(cpu, buffer->cpumask))
return NULL;
event = ring_buffer_peek(buffer, cpu, ts);
if (!event)
return NULL;
cpu_buffer = buffer->buffers[cpu];
rb_advance_reader(cpu_buffer);
return event;
}
/**
* ring_buffer_read_start - start a non consuming read of the buffer
* @buffer: The ring buffer to read from
* @cpu: The cpu buffer to iterate over
*
* This starts up an iteration through the buffer. It also disables
* the recording to the buffer until the reading is finished.
* This prevents the reading from being corrupted. This is not
* a consuming read, so a producer is not expected.
*
* Must be paired with ring_buffer_finish.
*/
struct ring_buffer_iter *
ring_buffer_read_start(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_iter *iter;
unsigned long flags;
if (!cpu_isset(cpu, buffer->cpumask))
return NULL;
iter = kmalloc(sizeof(*iter), GFP_KERNEL);
if (!iter)
return NULL;
cpu_buffer = buffer->buffers[cpu];
iter->cpu_buffer = cpu_buffer;
atomic_inc(&cpu_buffer->record_disabled);
synchronize_sched();
spin_lock_irqsave(&cpu_buffer->lock, flags);
ring_buffer_iter_reset(iter);
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
return iter;
}
/**
* ring_buffer_finish - finish reading the iterator of the buffer
* @iter: The iterator retrieved by ring_buffer_start
*
* This re-enables the recording to the buffer, and frees the
* iterator.
*/
void
ring_buffer_read_finish(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
atomic_dec(&cpu_buffer->record_disabled);
kfree(iter);
}
/**
* ring_buffer_read - read the next item in the ring buffer by the iterator
* @iter: The ring buffer iterator
* @ts: The time stamp of the event read.
*
* This reads the next event in the ring buffer and increments the iterator.
*/
struct ring_buffer_event *
ring_buffer_read(struct ring_buffer_iter *iter, u64 *ts)
{
struct ring_buffer_event *event;
event = ring_buffer_iter_peek(iter, ts);
if (!event)
return NULL;
rb_advance_iter(iter);
return event;
}
/**
* ring_buffer_size - return the size of the ring buffer (in bytes)
* @buffer: The ring buffer.
*/
unsigned long ring_buffer_size(struct ring_buffer *buffer)
{
return BUF_PAGE_SIZE * buffer->pages;
}
static void
rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer)
{
cpu_buffer->head_page
= list_entry(cpu_buffer->pages.next, struct buffer_page, list);
local_set(&cpu_buffer->head_page->write, 0);
local_set(&cpu_buffer->head_page->commit, 0);
cpu_buffer->head_page->read = 0;
cpu_buffer->tail_page = cpu_buffer->head_page;
cpu_buffer->commit_page = cpu_buffer->head_page;
INIT_LIST_HEAD(&cpu_buffer->reader_page->list);
local_set(&cpu_buffer->reader_page->write, 0);
local_set(&cpu_buffer->reader_page->commit, 0);
cpu_buffer->reader_page->read = 0;
cpu_buffer->overrun = 0;
cpu_buffer->entries = 0;
}
/**
* ring_buffer_reset_cpu - reset a ring buffer per CPU buffer
* @buffer: The ring buffer to reset a per cpu buffer of
* @cpu: The CPU buffer to be reset
*/
void ring_buffer_reset_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
unsigned long flags;
if (!cpu_isset(cpu, buffer->cpumask))
return;
spin_lock_irqsave(&cpu_buffer->lock, flags);
rb_reset_cpu(cpu_buffer);
spin_unlock_irqrestore(&cpu_buffer->lock, flags);
}
/**
* ring_buffer_reset - reset a ring buffer
* @buffer: The ring buffer to reset all cpu buffers
*/
void ring_buffer_reset(struct ring_buffer *buffer)
{
int cpu;
for_each_buffer_cpu(buffer, cpu)
ring_buffer_reset_cpu(buffer, cpu);
}
/**
* rind_buffer_empty - is the ring buffer empty?
* @buffer: The ring buffer to test
*/
int ring_buffer_empty(struct ring_buffer *buffer)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu;
/* yes this is racy, but if you don't like the race, lock the buffer */
for_each_buffer_cpu(buffer, cpu) {
cpu_buffer = buffer->buffers[cpu];
if (!rb_per_cpu_empty(cpu_buffer))
return 0;
}
return 1;
}
/**
* ring_buffer_empty_cpu - is a cpu buffer of a ring buffer empty?
* @buffer: The ring buffer
* @cpu: The CPU buffer to test
*/
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
if (!cpu_isset(cpu, buffer->cpumask))
return 1;
cpu_buffer = buffer->buffers[cpu];
return rb_per_cpu_empty(cpu_buffer);
}
/**
* ring_buffer_swap_cpu - swap a CPU buffer between two ring buffers
* @buffer_a: One buffer to swap with
* @buffer_b: The other buffer to swap with
*
* This function is useful for tracers that want to take a "snapshot"
* of a CPU buffer and has another back up buffer lying around.
* it is expected that the tracer handles the cpu buffer not being
* used at the moment.
*/
int ring_buffer_swap_cpu(struct ring_buffer *buffer_a,
struct ring_buffer *buffer_b, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
if (!cpu_isset(cpu, buffer_a->cpumask) ||
!cpu_isset(cpu, buffer_b->cpumask))
return -EINVAL;
/* At least make sure the two buffers are somewhat the same */
if (buffer_a->size != buffer_b->size ||
buffer_a->pages != buffer_b->pages)
return -EINVAL;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
/*
* We can't do a synchronize_sched here because this
* function can be called in atomic context.
* Normally this will be called from the same CPU as cpu.
* If not it's up to the caller to protect this.
*/
atomic_inc(&cpu_buffer_a->record_disabled);
atomic_inc(&cpu_buffer_b->record_disabled);
buffer_a->buffers[cpu] = cpu_buffer_b;
buffer_b->buffers[cpu] = cpu_buffer_a;
cpu_buffer_b->buffer = buffer_a;
cpu_buffer_a->buffer = buffer_b;
atomic_dec(&cpu_buffer_a->record_disabled);
atomic_dec(&cpu_buffer_b->record_disabled);
return 0;
}
static ssize_t
rb_simple_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
int *p = filp->private_data;
char buf[64];
int r;
/* !ring_buffers_off == tracing_on */
r = sprintf(buf, "%d\n", !*p);
return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
}
static ssize_t
rb_simple_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
int *p = filp->private_data;
char buf[64];
long val;
int ret;
if (cnt >= sizeof(buf))
return -EINVAL;
if (copy_from_user(&buf, ubuf, cnt))
return -EFAULT;
buf[cnt] = 0;
ret = strict_strtoul(buf, 10, &val);
if (ret < 0)
return ret;
/* !ring_buffers_off == tracing_on */
*p = !val;
(*ppos)++;
return cnt;
}
static struct file_operations rb_simple_fops = {
.open = tracing_open_generic,
.read = rb_simple_read,
.write = rb_simple_write,
};
static __init int rb_init_debugfs(void)
{
struct dentry *d_tracer;
struct dentry *entry;
d_tracer = tracing_init_dentry();
entry = debugfs_create_file("tracing_on", 0644, d_tracer,
&ring_buffers_off, &rb_simple_fops);
if (!entry)
pr_warning("Could not create debugfs 'tracing_on' entry\n");
return 0;
}
fs_initcall(rb_init_debugfs);