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tracing/ring-buffer: Only have tracing_on disable tracing buffers

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As the ring-buffer code is being used by other facilities in the
kernel, having tracing_on file disable *all* buffers is not a desired
affect. It should only disable the ftrace buffers that are being used.

Move the code into the trace.c file and use the buffer disabling
for tracing_on() and tracing_off(). This way only the ftrace buffers
will be affected by them and other kernel utilities will not be
confused to why their output suddenly stopped.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2012-02-22 15:50:28 -05:00 committed by Steven Rostedt
parent 5500fa5119
commit 499e547057
4 changed files with 171 additions and 97 deletions
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3
include/linux/ring_buffer.h
View file

@ -151,6 +151,9 @@ int ring_buffer_empty_cpu(struct ring_buffer *buffer, int cpu);
void ring_buffer_record_disable(struct ring_buffer *buffer);
void ring_buffer_record_enable(struct ring_buffer *buffer);
void ring_buffer_record_off(struct ring_buffer *buffer);
void ring_buffer_record_on(struct ring_buffer *buffer);
int ring_buffer_record_is_on(struct ring_buffer *buffer);
void ring_buffer_record_disable_cpu(struct ring_buffer *buffer, int cpu);
void ring_buffer_record_enable_cpu(struct ring_buffer *buffer, int cpu);

157
kernel/trace/ring_buffer.c
View file

@ -154,34 +154,11 @@ enum {
static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON;
/* Used for individual buffers (after the counter) */
#define RB_BUFFER_OFF (1 << 20)
#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
*
@ -193,15 +170,6 @@ 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);
#define RB_EVNT_HDR_SIZE (offsetof(struct ring_buffer_event, array))
#define RB_ALIGNMENT 4U
#define RB_MAX_SMALL_DATA (RB_ALIGNMENT * RINGBUF_TYPE_DATA_TYPE_LEN_MAX)
@ -2618,6 +2586,63 @@ void ring_buffer_record_enable(struct ring_buffer *buffer)
}
EXPORT_SYMBOL_GPL(ring_buffer_record_enable);
/**
* ring_buffer_record_off - 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.
*
* This is different than ring_buffer_record_disable() as
* it works like an on/off switch, where as the disable() verison
* must be paired with a enable().
*/
void ring_buffer_record_off(struct ring_buffer *buffer)
{
unsigned int rd;
unsigned int new_rd;
do {
rd = atomic_read(&buffer->record_disabled);
new_rd = rd | RB_BUFFER_OFF;
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_off);
/**
* ring_buffer_record_on - restart writes into the buffer
* @buffer: The ring buffer to start writes to.
*
* This enables all writes to the buffer that was disabled by
* ring_buffer_record_off().
*
* This is different than ring_buffer_record_enable() as
* it works like an on/off switch, where as the enable() verison
* must be paired with a disable().
*/
void ring_buffer_record_on(struct ring_buffer *buffer)
{
unsigned int rd;
unsigned int new_rd;
do {
rd = atomic_read(&buffer->record_disabled);
new_rd = rd & ~RB_BUFFER_OFF;
} while (atomic_cmpxchg(&buffer->record_disabled, rd, new_rd) != rd);
}
EXPORT_SYMBOL_GPL(ring_buffer_record_on);
/**
* ring_buffer_record_is_on - return true if the ring buffer can write
* @buffer: The ring buffer to see if write is enabled
*
* Returns true if the ring buffer is in a state that it accepts writes.
*/
int ring_buffer_record_is_on(struct ring_buffer *buffer)
{
return !atomic_read(&buffer->record_disabled);
}
/**
* ring_buffer_record_disable_cpu - stop all writes into the cpu_buffer
* @buffer: The ring buffer to stop writes to.
@ -4039,68 +4064,6 @@ int ring_buffer_read_page(struct ring_buffer *buffer,
}
EXPORT_SYMBOL_GPL(ring_buffer_read_page);
#ifdef CONFIG_TRACING
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;
unsigned long val;
int ret;
ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
if (ret)
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,
.llseek = default_llseek,
};
static __init int rb_init_debugfs(void)
{
struct dentry *d_tracer;
d_tracer = tracing_init_dentry();
trace_create_file("tracing_on", 0644, d_tracer,
&ring_buffer_flags, &rb_simple_fops);
return 0;
}
fs_initcall(rb_init_debugfs);
#endif
#ifdef CONFIG_HOTPLUG_CPU
static int rb_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)

107
kernel/trace/trace.c
View file

@ -351,6 +351,59 @@ static void wakeup_work_handler(struct work_struct *work)
static DECLARE_DELAYED_WORK(wakeup_work, wakeup_work_handler);
/**
* tracing_on - enable tracing buffers
*
* This function enables tracing buffers that may have been
* disabled with tracing_off.
*/
void tracing_on(void)
{
if (global_trace.buffer)
ring_buffer_record_on(global_trace.buffer);
/*
* This flag is only looked at when buffers haven't been
* allocated yet. We don't really care about the race
* between setting this flag and actually turning
* on the buffer.
*/
global_trace.buffer_disabled = 0;
}
EXPORT_SYMBOL_GPL(tracing_on);
/**
* tracing_off - turn off tracing buffers
*
* This function stops the 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)
{
if (global_trace.buffer)
ring_buffer_record_on(global_trace.buffer);
/*
* This flag is only looked at when buffers haven't been
* allocated yet. We don't really care about the race
* between setting this flag and actually turning
* on the buffer.
*/
global_trace.buffer_disabled = 1;
}
EXPORT_SYMBOL_GPL(tracing_off);
/**
* tracing_is_on - show state of ring buffers enabled
*/
int tracing_is_on(void)
{
if (global_trace.buffer)
return ring_buffer_record_is_on(global_trace.buffer);
return !global_trace.buffer_disabled;
}
EXPORT_SYMBOL_GPL(tracing_is_on);
/**
* trace_wake_up - wake up tasks waiting for trace input
*
@ -4567,6 +4620,55 @@ static __init void create_trace_options_dir(void)
create_trace_option_core_file(trace_options[i], i);
}
static ssize_t
rb_simple_read(struct file *filp, char __user *ubuf,
size_t cnt, loff_t *ppos)
{
struct ring_buffer *buffer = filp->private_data;
char buf[64];
int r;
if (buffer)
r = ring_buffer_record_is_on(buffer);
else
r = 0;
r = sprintf(buf, "%d\n", r);
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)
{
struct ring_buffer *buffer = filp->private_data;
unsigned long val;
int ret;
ret = kstrtoul_from_user(ubuf, cnt, 10, &val);
if (ret)
return ret;
if (buffer) {
if (val)
ring_buffer_record_on(buffer);
else
ring_buffer_record_off(buffer);
}
(*ppos)++;
return cnt;
}
static const struct file_operations rb_simple_fops = {
.open = tracing_open_generic,
.read = rb_simple_read,
.write = rb_simple_write,
.llseek = default_llseek,
};
static __init int tracer_init_debugfs(void)
{
struct dentry *d_tracer;
@ -4626,6 +4728,9 @@ static __init int tracer_init_debugfs(void)
trace_create_file("trace_clock", 0644, d_tracer, NULL,
&trace_clock_fops);
trace_create_file("tracing_on", 0644, d_tracer,
global_trace.buffer, &rb_simple_fops);
#ifdef CONFIG_DYNAMIC_FTRACE
trace_create_file("dyn_ftrace_total_info", 0444, d_tracer,
&ftrace_update_tot_cnt, &tracing_dyn_info_fops);
@ -4863,6 +4968,8 @@ __init static int tracer_alloc_buffers(void)
goto out_free_cpumask;
}
global_trace.entries = ring_buffer_size(global_trace.buffer);
if (global_trace.buffer_disabled)
tracing_off();
#ifdef CONFIG_TRACER_MAX_TRACE

1
kernel/trace/trace.h
View file

@ -154,6 +154,7 @@ struct trace_array {
struct ring_buffer *buffer;
unsigned long entries;
int cpu;
int buffer_disabled;
cycle_t time_start;
struct task_struct *waiter;
struct trace_array_cpu *data[NR_CPUS];