* Copyright (C) 2008 Steven Rostedt <srostedt@redhat.com>
*/
#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/sched.h> /* used for sched_clock() (for now) */
#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 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
RB_BUFFERS_DISABLED = 1 << RB_BUFFERS_DISABLED_BIT,
};
-static long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
+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
* tracing_off_permanent - permanently disable ring buffers
*
* This function, once called, will disable all ring buffers
- * permanenty.
+ * 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"
-/* Up this if you want to test the TIME_EXTENTS and normalization */
-#define DEBUG_SHIFT 0
+#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,
+};
-/* FIXME!!! */
-u64 ring_buffer_time_stamp(int cpu)
+static inline int rb_null_event(struct ring_buffer_event *event)
{
- u64 time;
+ return event->type == RINGBUF_TYPE_PADDING && event->time_delta == 0;
+}
- preempt_disable_notrace();
- /* shift to debug/test normalization and TIME_EXTENTS */
- time = sched_clock() << DEBUG_SHIFT;
- preempt_enable_no_resched_notrace();
+static inline int rb_discarded_event(struct ring_buffer_event *event)
+{
+ return event->type == RINGBUF_TYPE_PADDING && event->time_delta;
+}
- return time;
+static void rb_event_set_padding(struct ring_buffer_event *event)
+{
+ event->type = RINGBUF_TYPE_PADDING;
+ event->time_delta = 0;
}
-EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
-void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
+/**
+ * ring_buffer_event_discard - discard an event in the ring buffer
+ * @buffer: the ring buffer
+ * @event: the event to discard
+ *
+ * Sometimes a event that is in the ring buffer needs to be ignored.
+ * This function lets the user discard an event in the ring buffer
+ * and then that event will not be read later.
+ *
+ * Note, it is up to the user to be careful with this, and protect
+ * against races. If the user discards an event that has been consumed
+ * it is possible that it could corrupt the ring buffer.
+ */
+void ring_buffer_event_discard(struct ring_buffer_event *event)
{
- /* Just stupid testing the normalize function and deltas */
- *ts >>= DEBUG_SHIFT;
+ event->type = RINGBUF_TYPE_PADDING;
+ /* time delta must be non zero */
+ if (!event->time_delta)
+ event->time_delta = 1;
}
-EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
-#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
+static unsigned
+rb_event_data_length(struct ring_buffer_event *event)
+{
+ unsigned length;
-enum {
- RB_LEN_TIME_EXTEND = 8,
- RB_LEN_TIME_STAMP = 16,
-};
+ 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 inline unsigned
+static unsigned
rb_event_length(struct ring_buffer_event *event)
{
- unsigned length;
-
switch (event->type) {
case RINGBUF_TYPE_PADDING:
- /* undefined */
- return -1;
+ if (rb_null_event(event))
+ /* undefined */
+ return -1;
+ return rb_event_data_length(event);
case RINGBUF_TYPE_TIME_EXTEND:
return RB_LEN_TIME_EXTEND;
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;
+ return rb_event_data_length(event);
default:
BUG();
}
EXPORT_SYMBOL_GPL(ring_buffer_event_length);
/* inline for ring buffer fast paths */
-static inline void *
+static void *
rb_event_data(struct ring_buffer_event *event)
{
BUG_ON(event->type != RINGBUF_TYPE_DATA);
struct buffer_data_page {
u64 time_stamp; /* page time stamp */
- local_t commit; /* write commited index */
+ local_t commit; /* write committed index */
unsigned char data[]; /* data of buffer page */
};
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 Mathieu Desnoyers for pointing
* this issue out.
*/
-static inline void free_buffer_page(struct buffer_page *bpage)
+static void free_buffer_page(struct buffer_page *bpage)
{
- if (bpage->page)
- free_page((unsigned long)bpage->page);
+ free_page((unsigned long)bpage->page);
kfree(bpage);
}
return 0;
}
-#define BUF_PAGE_SIZE (PAGE_SIZE - offsetof(struct buffer_data_page, data))
+#define BUF_PAGE_SIZE (PAGE_SIZE - BUF_PAGE_HDR_SIZE)
/*
* head_page == tail_page && head == tail then buffer is empty.
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 *commit_page; /* committed pages */
struct buffer_page *reader_page;
unsigned long overrun;
unsigned long entries;
unsigned pages;
unsigned flags;
int cpus;
- cpumask_var_t cpumask;
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 {
_____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 safty measure we check to make sure the data pages have not
+ * 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;
- list_del_init(&cpu_buffer->reader_page->list);
free_buffer_page(cpu_buffer->reader_page);
list_for_each_entry_safe(bpage, tmp, head, list) {
*/
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.
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;
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_cpumask:
free_cpumask_var(buffer->cpumask);
+ put_online_cpus();
fail_free_buffer:
kfree(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
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)) {
- mutex_unlock(&buffer->mutex);
- return -1;
- }
+ if (RB_WARN_ON(buffer, nr_pages >= buffer->pages))
+ goto out_fail;
rm_pages = buffer->pages - nr_pages;
* 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)) {
- mutex_unlock(&buffer->mutex);
- return -1;
- }
+ if (RB_WARN_ON(buffer, nr_pages <= buffer->pages))
+ goto out_fail;
new_pages = nr_pages - buffer->pages;
rb_insert_pages(cpu_buffer, &pages, new_pages);
}
- if (RB_WARN_ON(buffer, !list_empty(&pages))) {
- mutex_unlock(&buffer->mutex);
- return -1;
- }
+ 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;
list_del_init(&bpage->list);
free_buffer_page(bpage);
}
+ put_online_cpus();
mutex_unlock(&buffer->mutex);
return -ENOMEM;
-}
-EXPORT_SYMBOL_GPL(ring_buffer_resize);
-static inline int rb_null_event(struct ring_buffer_event *event)
-{
- return event->type == RINGBUF_TYPE_PADDING;
+ /*
+ * 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 (addr & ~PAGE_MASK) - (PAGE_SIZE - BUF_PAGE_SIZE);
}
-static inline int
+static int
rb_is_commit(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
rb_commit_index(cpu_buffer) == index;
}
-static inline void
+static void
rb_set_commit_event(struct ring_buffer_per_cpu *cpu_buffer,
struct ring_buffer_event *event)
{
local_set(&cpu_buffer->commit_page->page->commit, index);
}
-static inline void
+static void
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
{
/*
cpu_buffer->reader_page->read = 0;
}
-static inline void rb_inc_iter(struct ring_buffer_iter *iter)
+static void rb_inc_iter(struct ring_buffer_iter *iter)
{
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
* and with this, we can determine what to place into the
* data field.
*/
-static inline void
+static void
rb_update_event(struct ring_buffer_event *event,
unsigned type, unsigned length)
{
break;
case RINGBUF_TYPE_TIME_EXTEND:
- event->len =
- (RB_LEN_TIME_EXTEND + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
+ event->len = DIV_ROUND_UP(RB_LEN_TIME_EXTEND, RB_ALIGNMENT);
break;
case RINGBUF_TYPE_TIME_STAMP:
- event->len =
- (RB_LEN_TIME_STAMP + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
+ event->len = DIV_ROUND_UP(RB_LEN_TIME_STAMP, RB_ALIGNMENT);
break;
case RINGBUF_TYPE_DATA:
event->len = 0;
event->array[0] = length;
} else
- event->len =
- (length + (RB_ALIGNMENT-1))
- >> RB_ALIGNMENT_SHIFT;
+ event->len = DIV_ROUND_UP(length, RB_ALIGNMENT);
break;
default:
BUG();
}
}
-static inline unsigned rb_calculate_event_length(unsigned length)
+static unsigned rb_calculate_event_length(unsigned length)
{
struct ring_buffer_event event; /* Used only for sizeof array */
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 */
struct buffer_page *next_page = tail_page;
local_irq_save(flags);
- __raw_spin_lock(&cpu_buffer->lock);
+ /*
+ * 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);
/* we grabbed the lock before incrementing */
if (RB_WARN_ON(cpu_buffer, next_page == reader_page))
- goto out_unlock;
+ goto out_reset;
/*
* If for some reason, we had an interrupt storm that made
*/
if (unlikely(next_page == commit_page)) {
WARN_ON_ONCE(1);
- goto out_unlock;
+ goto out_reset;
}
if (next_page == head_page) {
if (!(buffer->flags & RB_FL_OVERWRITE))
- goto out_unlock;
+ goto out_reset;
/* tail_page has not moved yet? */
if (tail_page == cpu_buffer->tail_page) {
cpu_buffer->tail_page = next_page;
/* reread the time stamp */
- *ts = ring_buffer_time_stamp(cpu_buffer->cpu);
+ *ts = ring_buffer_time_stamp(buffer, cpu_buffer->cpu);
cpu_buffer->tail_page->page->time_stamp = *ts;
}
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;
+ rb_event_set_padding(event);
}
if (tail <= BUF_PAGE_SIZE)
return event;
- out_unlock:
+ out_reset:
/* reset write */
if (tail <= BUF_PAGE_SIZE)
local_set(&tail_page->write, tail);
- __raw_spin_unlock(&cpu_buffer->lock);
+ if (likely(lock_taken))
+ __raw_spin_unlock(&cpu_buffer->lock);
local_irq_restore(flags);
return NULL;
}
if (RB_WARN_ON(cpu_buffer, ++nr_loops > 1000))
return NULL;
- ts = ring_buffer_time_stamp(cpu_buffer->cpu);
+ ts = ring_buffer_time_stamp(cpu_buffer->buffer, cpu_buffer->cpu);
/*
* Only the first commit can update the timestamp.
* 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
* 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)
+ring_buffer_lock_reserve(struct ring_buffer *buffer, unsigned long length)
{
struct ring_buffer_per_cpu *cpu_buffer;
struct ring_buffer_event *event;
* 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_event *event)
{
struct ring_buffer_per_cpu *cpu_buffer;
int cpu = raw_smp_processor_id();
}
EXPORT_SYMBOL_GPL(ring_buffer_write);
-static inline int rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer)
+static 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;
unsigned long ring_buffer_entries_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
- return cpu_buffer->entries;
+ ret = cpu_buffer->entries;
+
+ return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
unsigned long ring_buffer_overrun_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ unsigned long ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 0;
cpu_buffer = buffer->buffers[cpu];
- return cpu_buffer->overrun;
+ ret = cpu_buffer->overrun;
+
+ return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
*/
void ring_buffer_iter_reset(struct ring_buffer_iter *iter)
{
- struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
+ struct ring_buffer_per_cpu *cpu_buffer;
unsigned long flags;
+ if (!iter)
+ return;
+
+ cpu_buffer = iter->cpu_buffer;
+
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
rb_iter_reset(iter);
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
event = rb_reader_event(cpu_buffer);
- if (event->type == RINGBUF_TYPE_DATA)
+ if (event->type == RINGBUF_TYPE_DATA || rb_discarded_event(event))
cpu_buffer->entries--;
rb_update_read_stamp(cpu_buffer, event);
struct buffer_page *reader;
int nr_loops = 0;
- if (!cpumask_test_cpu(cpu, buffer->cpumask))
- return NULL;
-
cpu_buffer = buffer->buffers[cpu];
again:
switch (event->type) {
case RINGBUF_TYPE_PADDING:
- RB_WARN_ON(cpu_buffer, 1);
+ if (rb_null_event(event))
+ RB_WARN_ON(cpu_buffer, 1);
+ /*
+ * Because the writer could be discarding every
+ * event it creates (which would probably be bad)
+ * if we were to go back to "again" then we may never
+ * catch up, and will trigger the warn on, or lock
+ * the box. Return the padding, and we will release
+ * the current locks, and try again.
+ */
rb_advance_reader(cpu_buffer);
- return NULL;
+ return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = cpu_buffer->read_stamp + event->time_delta;
- ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
+ ring_buffer_normalize_time_stamp(buffer,
+ cpu_buffer->cpu, ts);
}
return event;
switch (event->type) {
case RINGBUF_TYPE_PADDING:
- rb_inc_iter(iter);
- goto again;
+ if (rb_null_event(event)) {
+ rb_inc_iter(iter);
+ goto again;
+ }
+ rb_advance_iter(iter);
+ return event;
case RINGBUF_TYPE_TIME_EXTEND:
/* Internal data, OK to advance */
case RINGBUF_TYPE_DATA:
if (ts) {
*ts = iter->read_stamp + event->time_delta;
- ring_buffer_normalize_time_stamp(cpu_buffer->cpu, ts);
+ ring_buffer_normalize_time_stamp(buffer,
+ cpu_buffer->cpu, ts);
}
return event;
struct ring_buffer_event *event;
unsigned long flags;
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ return NULL;
+
+ again:
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_buffer_peek(buffer, cpu, ts);
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+ if (event && event->type == RINGBUF_TYPE_PADDING) {
+ cpu_relax();
+ goto again;
+ }
+
return event;
}
struct ring_buffer_event *event;
unsigned long flags;
+ again:
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_iter_peek(iter, ts);
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+ if (event && event->type == RINGBUF_TYPE_PADDING) {
+ cpu_relax();
+ goto again;
+ }
+
return event;
}
struct ring_buffer_event *
ring_buffer_consume(struct ring_buffer *buffer, int cpu, u64 *ts)
{
- struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
- struct ring_buffer_event *event;
+ struct ring_buffer_per_cpu *cpu_buffer;
+ struct ring_buffer_event *event = NULL;
unsigned long flags;
+ again:
+ /* might be called in atomic */
+ preempt_disable();
+
if (!cpumask_test_cpu(cpu, buffer->cpumask))
- return NULL;
+ goto out;
+ cpu_buffer = buffer->buffers[cpu];
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_buffer_peek(buffer, cpu, ts);
if (!event)
- goto out;
+ goto out_unlock;
rb_advance_reader(cpu_buffer);
- out:
+ out_unlock:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+ out:
+ preempt_enable();
+
+ if (event && event->type == RINGBUF_TYPE_PADDING) {
+ cpu_relax();
+ goto again;
+ }
+
return event;
}
EXPORT_SYMBOL_GPL(ring_buffer_consume);
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
unsigned long flags;
+ again:
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
event = rb_iter_peek(iter, ts);
if (!event)
out:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+ if (event && event->type == RINGBUF_TYPE_PADDING) {
+ cpu_relax();
+ goto again;
+ }
+
return event;
}
EXPORT_SYMBOL_GPL(ring_buffer_read);
if (!rb_per_cpu_empty(cpu_buffer))
return 0;
}
+
return 1;
}
EXPORT_SYMBOL_GPL(ring_buffer_empty);
int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu)
{
struct ring_buffer_per_cpu *cpu_buffer;
+ int ret;
if (!cpumask_test_cpu(cpu, buffer->cpumask))
return 1;
cpu_buffer = buffer->buffers[cpu];
- return rb_per_cpu_empty(cpu_buffer);
+ ret = rb_per_cpu_empty(cpu_buffer);
+
+
+ return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
{
struct ring_buffer_per_cpu *cpu_buffer_a;
struct ring_buffer_per_cpu *cpu_buffer_b;
+ int ret = -EINVAL;
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
!cpumask_test_cpu(cpu, buffer_b->cpumask))
- return -EINVAL;
+ goto out;
/* At least make sure the two buffers are somewhat the same */
if (buffer_a->pages != buffer_b->pages)
- return -EINVAL;
+ goto out;
+
+ ret = -EAGAIN;
+
+ if (ring_buffer_flags != RB_BUFFERS_ON)
+ goto out;
+
+ if (atomic_read(&buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&buffer_b->record_disabled))
+ goto out;
cpu_buffer_a = buffer_a->buffers[cpu];
cpu_buffer_b = buffer_b->buffers[cpu];
+ if (atomic_read(&cpu_buffer_a->record_disabled))
+ goto out;
+
+ if (atomic_read(&cpu_buffer_b->record_disabled))
+ goto out;
+
/*
* We can't do a synchronize_sched here because this
* function can be called in atomic context.
atomic_dec(&cpu_buffer_a->record_disabled);
atomic_dec(&cpu_buffer_b->record_disabled);
- return 0;
+ ret = 0;
+out:
+ return ret;
}
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);
static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,
- struct buffer_data_page *bpage)
+ struct buffer_data_page *bpage,
+ unsigned int offset)
{
struct ring_buffer_event *event;
unsigned long head;
__raw_spin_lock(&cpu_buffer->lock);
- for (head = 0; head < local_read(&bpage->commit);
+ for (head = offset; head < local_read(&bpage->commit);
head += rb_event_length(event)) {
event = __rb_data_page_index(bpage, head);
*/
void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
{
- unsigned long addr;
struct buffer_data_page *bpage;
+ unsigned long addr;
addr = __get_free_page(GFP_KERNEL);
if (!addr)
bpage = (void *)addr;
+ rb_init_page(bpage);
+
return bpage;
}
* ring_buffer_read_page - extract a page from the ring buffer
* @buffer: buffer to extract from
* @data_page: the page to use allocated from ring_buffer_alloc_read_page
+ * @len: amount to extract
* @cpu: the cpu of the buffer to extract
* @full: should the extraction only happen when the page is full.
*
* to swap with a page in the ring buffer.
*
* for example:
- * rpage = ring_buffer_alloc_page(buffer);
+ * rpage = ring_buffer_alloc_read_page(buffer);
* if (!rpage)
* return error;
- * ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);
- * if (ret)
- * process_page(rpage);
+ * ret = ring_buffer_read_page(buffer, &rpage, len, cpu, 0);
+ * if (ret >= 0)
+ * process_page(rpage, ret);
*
* When @full is set, the function will not return true unless
* the writer is off the reader page.
* responsible for that.
*
* Returns:
- * 1 if data has been transferred
- * 0 if no data has been transferred.
+ * >=0 if data has been transferred, returns the offset of consumed data.
+ * <0 if no data has been transferred.
*/
int ring_buffer_read_page(struct ring_buffer *buffer,
- void **data_page, int cpu, int full)
+ void **data_page, size_t len, int cpu, int full)
{
struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu];
struct ring_buffer_event *event;
struct buffer_data_page *bpage;
+ struct buffer_page *reader;
unsigned long flags;
- int ret = 0;
+ unsigned int commit;
+ unsigned int read;
+ u64 save_timestamp;
+ int ret = -1;
+
+ if (!cpumask_test_cpu(cpu, buffer->cpumask))
+ goto out;
+
+ /*
+ * If len is not big enough to hold the page header, then
+ * we can not copy anything.
+ */
+ if (len <= BUF_PAGE_HDR_SIZE)
+ goto out;
+
+ len -= BUF_PAGE_HDR_SIZE;
if (!data_page)
- return 0;
+ goto out;
bpage = *data_page;
if (!bpage)
- return 0;
+ goto out;
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
- /*
- * rb_buffer_peek will get the next ring buffer if
- * the current reader page is empty.
- */
- event = rb_buffer_peek(buffer, cpu, NULL);
- if (!event)
- goto out;
+ reader = rb_get_reader_page(cpu_buffer);
+ if (!reader)
+ goto out_unlock;
+
+ event = rb_reader_event(cpu_buffer);
+
+ read = reader->read;
+ commit = rb_page_commit(reader);
- /* check for data */
- if (!local_read(&cpu_buffer->reader_page->page->commit))
- goto out;
/*
- * If the writer is already off of the read page, then simply
- * switch the read page with the given page. Otherwise
- * we need to copy the data from the reader to the writer.
+ * If this page has been partially read or
+ * if len is not big enough to read the rest of the page or
+ * a writer is still on the page, then
+ * we must copy the data from the page to the buffer.
+ * Otherwise, we can simply swap the page with the one passed in.
*/
- if (cpu_buffer->reader_page == cpu_buffer->commit_page) {
- unsigned int read = cpu_buffer->reader_page->read;
+ if (read || (len < (commit - read)) ||
+ cpu_buffer->reader_page == cpu_buffer->commit_page) {
+ struct buffer_data_page *rpage = cpu_buffer->reader_page->page;
+ unsigned int rpos = read;
+ unsigned int pos = 0;
+ unsigned int size;
if (full)
- goto out;
- /* The writer is still on the reader page, we must copy */
- bpage = cpu_buffer->reader_page->page;
- memcpy(bpage->data,
- cpu_buffer->reader_page->page->data + read,
- local_read(&bpage->commit) - read);
+ goto out_unlock;
+
+ if (len > (commit - read))
+ len = (commit - read);
+
+ size = rb_event_length(event);
+
+ if (len < size)
+ goto out_unlock;
- /* consume what was read */
- cpu_buffer->reader_page += read;
+ /* save the current timestamp, since the user will need it */
+ save_timestamp = cpu_buffer->read_stamp;
+ /* Need to copy one event at a time */
+ do {
+ memcpy(bpage->data + pos, rpage->data + rpos, size);
+
+ len -= size;
+
+ rb_advance_reader(cpu_buffer);
+ rpos = reader->read;
+ pos += size;
+
+ event = rb_reader_event(cpu_buffer);
+ size = rb_event_length(event);
+ } while (len > size);
+
+ /* update bpage */
+ local_set(&bpage->commit, pos);
+ bpage->time_stamp = save_timestamp;
+
+ /* we copied everything to the beginning */
+ read = 0;
} else {
/* swap the pages */
rb_init_page(bpage);
- bpage = cpu_buffer->reader_page->page;
- cpu_buffer->reader_page->page = *data_page;
- cpu_buffer->reader_page->read = 0;
+ bpage = reader->page;
+ reader->page = *data_page;
+ local_set(&reader->write, 0);
+ reader->read = 0;
*data_page = bpage;
+
+ /* update the entry counter */
+ rb_remove_entries(cpu_buffer, bpage, read);
}
- ret = 1;
+ ret = read;
- /* update the entry counter */
- rb_remove_entries(cpu_buffer, bpage);
- out:
+ out_unlock:
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
+ out:
return ret;
}
rb_simple_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
- long *p = filp->private_data;
+ unsigned long *p = filp->private_data;
char buf[64];
int r;
rb_simple_write(struct file *filp, const char __user *ubuf,
size_t cnt, loff_t *ppos)
{
- long *p = filp->private_data;
+ unsigned long *p = filp->private_data;
char buf[64];
- long val;
+ unsigned long val;
int ret;
if (cnt >= sizeof(buf))
return cnt;
}
-static struct file_operations rb_simple_fops = {
+static const struct file_operations rb_simple_fops = {
.open = tracing_open_generic,
.read = rb_simple_read,
.write = rb_simple_write,
}
fs_initcall(rb_init_debugfs);
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int rb_cpu_notify(struct notifier_block *self,
+ unsigned long action, void *hcpu)
+{
+ struct ring_buffer *buffer =
+ container_of(self, struct ring_buffer, cpu_notify);
+ long cpu = (long)hcpu;
+
+ switch (action) {
+ case CPU_UP_PREPARE:
+ case CPU_UP_PREPARE_FROZEN:
+ if (cpu_isset(cpu, *buffer->cpumask))
+ return NOTIFY_OK;
+
+ buffer->buffers[cpu] =
+ rb_allocate_cpu_buffer(buffer, cpu);
+ if (!buffer->buffers[cpu]) {
+ WARN(1, "failed to allocate ring buffer on CPU %ld\n",
+ cpu);
+ return NOTIFY_OK;
+ }
+ smp_wmb();
+ cpu_set(cpu, *buffer->cpumask);
+ break;
+ case CPU_DOWN_PREPARE:
+ case CPU_DOWN_PREPARE_FROZEN:
+ /*
+ * Do nothing.
+ * If we were to free the buffer, then the user would
+ * lose any trace that was in the buffer.
+ */
+ break;
+ default:
+ break;
+ }
+ return NOTIFY_OK;
+}
+#endif
projects / linux-2.6-omap-h63xx.git / blobdiff