5cc9854888
In a private email conversation I explained how the ring buffer page worked by using silly ASCII art. Ingo suggested that I add that to the comments of the code. Here it is. Requested-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Steven Rostedt <srostedt@redhat.com>
2803 lines
68 KiB
C
2803 lines
68 KiB
C
/*
|
|
* Generic ring buffer
|
|
*
|
|
* 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/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
|
|
* 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"
|
|
|
|
/* Up this if you want to test the TIME_EXTENTS and normalization */
|
|
#define DEBUG_SHIFT 0
|
|
|
|
u64 ring_buffer_time_stamp(int cpu)
|
|
{
|
|
u64 time;
|
|
|
|
preempt_disable_notrace();
|
|
/* shift to debug/test normalization and TIME_EXTENTS */
|
|
time = trace_clock_local() << DEBUG_SHIFT;
|
|
preempt_enable_no_resched_notrace();
|
|
|
|
return time;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_time_stamp);
|
|
|
|
void ring_buffer_normalize_time_stamp(int cpu, u64 *ts)
|
|
{
|
|
/* Just stupid testing the normalize function and deltas */
|
|
*ts >>= DEBUG_SHIFT;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_normalize_time_stamp);
|
|
|
|
#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,
|
|
};
|
|
|
|
/* inline for ring buffer fast paths */
|
|
static 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;
|
|
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)
|
|
{
|
|
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 Mathieu Desnoyers 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)
|
|
|
|
/*
|
|
* 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
|
|
};
|
|
|
|
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; \
|
|
})
|
|
|
|
/**
|
|
* 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;
|
|
|
|
list_del_init(&cpu_buffer->reader_page->list);
|
|
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 __cpuinit 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;
|
|
|
|
/* need at least two pages */
|
|
if (buffer->pages == 1)
|
|
buffer->pages++;
|
|
|
|
get_online_cpus();
|
|
cpumask_copy(buffer->cpumask, cpu_online_mask);
|
|
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);
|
|
|
|
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 int rb_null_event(struct ring_buffer_event *event)
|
|
{
|
|
return event->type == RINGBUF_TYPE_PADDING;
|
|
}
|
|
|
|
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(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);
|
|
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);
|
|
}
|
|
|
|
__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->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)
|
|
*
|
|
* 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)
|
|
{
|
|
struct ring_buffer_per_cpu *cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
int cpu, resched;
|
|
|
|
if (ring_buffer_flags != RB_BUFFERS_ON)
|
|
return NULL;
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
return NULL;
|
|
|
|
/* If we are tracing schedule, we don't want to recurse */
|
|
resched = ftrace_preempt_disable();
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpumask_test_cpu(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:
|
|
ftrace_preempt_enable(resched);
|
|
return NULL;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_lock_reserve);
|
|
|
|
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.
|
|
*
|
|
* 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)
|
|
{
|
|
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)
|
|
ftrace_preempt_enable(per_cpu(rb_need_resched, cpu));
|
|
else
|
|
preempt_enable_no_resched_notrace();
|
|
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_unlock_commit);
|
|
|
|
/**
|
|
* 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_buffer_flags != RB_BUFFERS_ON)
|
|
return -EBUSY;
|
|
|
|
if (atomic_read(&buffer->record_disabled))
|
|
return -EBUSY;
|
|
|
|
resched = ftrace_preempt_disable();
|
|
|
|
cpu = raw_smp_processor_id();
|
|
|
|
if (!cpumask_test_cpu(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:
|
|
ftrace_preempt_enable(resched);
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_write);
|
|
|
|
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;
|
|
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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable);
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
|
|
|
|
/**
|
|
* 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 (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_inc(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_disable_cpu);
|
|
|
|
/**
|
|
* 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 (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
atomic_dec(&cpu_buffer->record_disabled);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_record_enable_cpu);
|
|
|
|
/**
|
|
* 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;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = cpu_buffer->entries;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_entries_cpu);
|
|
|
|
/**
|
|
* 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;
|
|
unsigned long ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 0;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = cpu_buffer->overrun;
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overrun_cpu);
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_overruns);
|
|
|
|
static void rb_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->page->time_stamp;
|
|
}
|
|
|
|
/**
|
|
* 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;
|
|
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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_reset);
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_empty);
|
|
|
|
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;
|
|
|
|
local_irq_save(flags);
|
|
__raw_spin_lock(&cpu_buffer->lock);
|
|
|
|
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 (RB_WARN_ON(cpu_buffer, ++nr_loops > 3)) {
|
|
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 */
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
cpu_buffer->reader_page->read > rb_page_size(reader)))
|
|
goto out;
|
|
|
|
/* 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->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:
|
|
__raw_spin_unlock(&cpu_buffer->lock);
|
|
local_irq_restore(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 */
|
|
if (RB_WARN_ON(cpu_buffer, !reader))
|
|
return;
|
|
|
|
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)) {
|
|
if (RB_WARN_ON(buffer,
|
|
iter->head_page == cpu_buffer->commit_page))
|
|
return;
|
|
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.
|
|
*/
|
|
if (RB_WARN_ON(cpu_buffer,
|
|
(iter->head_page == cpu_buffer->commit_page) &&
|
|
(iter->head + length > rb_commit_index(cpu_buffer))))
|
|
return;
|
|
|
|
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);
|
|
}
|
|
|
|
static struct ring_buffer_event *
|
|
rb_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;
|
|
|
|
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 (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
|
|
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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_peek);
|
|
|
|
static struct ring_buffer_event *
|
|
rb_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 (RB_WARN_ON(cpu_buffer, ++nr_loops > 10))
|
|
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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_iter_peek);
|
|
|
|
/**
|
|
* 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 = buffer->buffers[cpu];
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return NULL;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
event = rb_buffer_peek(buffer, cpu, ts);
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* 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_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
struct ring_buffer_event *event;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
event = rb_iter_peek(iter, ts);
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return event;
|
|
}
|
|
|
|
/**
|
|
* 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 = NULL;
|
|
unsigned long flags;
|
|
|
|
/* might be called in atomic */
|
|
preempt_disable();
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
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_unlock;
|
|
|
|
rb_advance_reader(cpu_buffer);
|
|
|
|
out_unlock:
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
out:
|
|
preempt_enable();
|
|
|
|
return event;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_consume);
|
|
|
|
/**
|
|
* 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 (!cpumask_test_cpu(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->reader_lock, flags);
|
|
__raw_spin_lock(&cpu_buffer->lock);
|
|
rb_iter_reset(iter);
|
|
__raw_spin_unlock(&cpu_buffer->lock);
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return iter;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_start);
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read_finish);
|
|
|
|
/**
|
|
* 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;
|
|
struct ring_buffer_per_cpu *cpu_buffer = iter->cpu_buffer;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
event = rb_iter_peek(iter, ts);
|
|
if (!event)
|
|
goto out;
|
|
|
|
rb_advance_iter(iter);
|
|
out:
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
return event;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_read);
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_size);
|
|
|
|
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->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->page->commit, 0);
|
|
cpu_buffer->reader_page->read = 0;
|
|
|
|
cpu_buffer->overrun = 0;
|
|
cpu_buffer->entries = 0;
|
|
|
|
cpu_buffer->write_stamp = 0;
|
|
cpu_buffer->read_stamp = 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 (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
__raw_spin_lock(&cpu_buffer->lock);
|
|
|
|
rb_reset_cpu(cpu_buffer);
|
|
|
|
__raw_spin_unlock(&cpu_buffer->lock);
|
|
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset_cpu);
|
|
|
|
/**
|
|
* 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);
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_reset);
|
|
|
|
/**
|
|
* 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;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty);
|
|
|
|
/**
|
|
* 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;
|
|
int ret;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer->cpumask))
|
|
return 1;
|
|
|
|
cpu_buffer = buffer->buffers[cpu];
|
|
ret = rb_per_cpu_empty(cpu_buffer);
|
|
|
|
|
|
return ret;
|
|
}
|
|
EXPORT_SYMBOL_GPL(ring_buffer_empty_cpu);
|
|
|
|
/**
|
|
* 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;
|
|
int ret = -EINVAL;
|
|
|
|
if (!cpumask_test_cpu(cpu, buffer_a->cpumask) ||
|
|
!cpumask_test_cpu(cpu, buffer_b->cpumask))
|
|
goto out;
|
|
|
|
/* At least make sure the two buffers are somewhat the same */
|
|
if (buffer_a->pages != buffer_b->pages)
|
|
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.
|
|
* 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);
|
|
|
|
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,
|
|
unsigned int offset)
|
|
{
|
|
struct ring_buffer_event *event;
|
|
unsigned long head;
|
|
|
|
__raw_spin_lock(&cpu_buffer->lock);
|
|
for (head = offset; head < local_read(&bpage->commit);
|
|
head += rb_event_length(event)) {
|
|
|
|
event = __rb_data_page_index(bpage, 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->entries--;
|
|
}
|
|
__raw_spin_unlock(&cpu_buffer->lock);
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_alloc_read_page - allocate a page to read from buffer
|
|
* @buffer: the buffer to allocate for.
|
|
*
|
|
* This function is used in conjunction with ring_buffer_read_page.
|
|
* When reading a full page from the ring buffer, these functions
|
|
* can be used to speed up the process. The calling function should
|
|
* allocate a few pages first with this function. Then when it
|
|
* needs to get pages from the ring buffer, it passes the result
|
|
* of this function into ring_buffer_read_page, which will swap
|
|
* the page that was allocated, with the read page of the buffer.
|
|
*
|
|
* Returns:
|
|
* The page allocated, or NULL on error.
|
|
*/
|
|
void *ring_buffer_alloc_read_page(struct ring_buffer *buffer)
|
|
{
|
|
struct buffer_data_page *bpage;
|
|
unsigned long addr;
|
|
|
|
addr = __get_free_page(GFP_KERNEL);
|
|
if (!addr)
|
|
return NULL;
|
|
|
|
bpage = (void *)addr;
|
|
|
|
rb_init_page(bpage);
|
|
|
|
return bpage;
|
|
}
|
|
|
|
/**
|
|
* ring_buffer_free_read_page - free an allocated read page
|
|
* @buffer: the buffer the page was allocate for
|
|
* @data: the page to free
|
|
*
|
|
* Free a page allocated from ring_buffer_alloc_read_page.
|
|
*/
|
|
void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data)
|
|
{
|
|
free_page((unsigned long)data);
|
|
}
|
|
|
|
/**
|
|
* 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.
|
|
*
|
|
* This function will pull out a page from the ring buffer and consume it.
|
|
* @data_page must be the address of the variable that was returned
|
|
* from ring_buffer_alloc_read_page. This is because the page might be used
|
|
* to swap with a page in the ring buffer.
|
|
*
|
|
* for example:
|
|
* rpage = ring_buffer_alloc_read_page(buffer);
|
|
* if (!rpage)
|
|
* return error;
|
|
* 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.
|
|
*
|
|
* Note: it is up to the calling functions to handle sleeps and wakeups.
|
|
* The ring buffer can be used anywhere in the kernel and can not
|
|
* blindly call wake_up. The layer that uses the ring buffer must be
|
|
* responsible for that.
|
|
*
|
|
* Returns:
|
|
* >=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, 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;
|
|
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)
|
|
goto out;
|
|
|
|
bpage = *data_page;
|
|
if (!bpage)
|
|
goto out;
|
|
|
|
spin_lock_irqsave(&cpu_buffer->reader_lock, flags);
|
|
|
|
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);
|
|
|
|
/*
|
|
* 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 (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_unlock;
|
|
|
|
if (len > (commit - read))
|
|
len = (commit - read);
|
|
|
|
size = rb_event_length(event);
|
|
|
|
if (len < size)
|
|
goto out_unlock;
|
|
|
|
/* 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 = 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 = read;
|
|
|
|
out_unlock:
|
|
spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);
|
|
|
|
out:
|
|
return ret;
|
|
}
|
|
|
|
static ssize_t
|
|
rb_simple_read(struct file *filp, char __user *ubuf,
|
|
size_t cnt, loff_t *ppos)
|
|
{
|
|
unsigned long *p = filp->private_data;
|
|
char buf[64];
|
|
int r;
|
|
|
|
if (test_bit(RB_BUFFERS_DISABLED_BIT, p))
|
|
r = sprintf(buf, "permanently disabled\n");
|
|
else
|
|
r = sprintf(buf, "%d\n", test_bit(RB_BUFFERS_ON_BIT, 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)
|
|
{
|
|
unsigned long *p = filp->private_data;
|
|
char buf[64];
|
|
unsigned 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;
|
|
|
|
if (val)
|
|
set_bit(RB_BUFFERS_ON_BIT, p);
|
|
else
|
|
clear_bit(RB_BUFFERS_ON_BIT, p);
|
|
|
|
(*ppos)++;
|
|
|
|
return cnt;
|
|
}
|
|
|
|
static const 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_buffer_flags, &rb_simple_fops);
|
|
if (!entry)
|
|
pr_warning("Could not create debugfs 'tracing_on' entry\n");
|
|
|
|
return 0;
|
|
}
|
|
|
|
fs_initcall(rb_init_debugfs);
|
|
|
|
#ifdef CONFIG_HOTPLUG_CPU
|
|
static int __cpuinit 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
|