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ring-buffer: Add interface for setting absolute time stamps

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Define a new function, tracing_set_time_stamp_abs(), which can be used
to enable or disable the use of absolute timestamps rather than time
deltas for a trace array.

Only the interface is added here; a subsequent patch will add the
underlying implementation.

Link: http://lkml.kernel.org/r/ce96119de44c7fe0ee44786d15254e9b493040d3.1516069914.git.tom.zanussi@linux.intel.com

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Baohong Liu <baohong.liu@intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Tom Zanussi 2018-01-15 20:51:39 -06:00 committed by Steven Rostedt (VMware)
parent c193707dde
commit 00b4145298
4 changed files with 48 additions and 1 deletions
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2
include/linux/ring_buffer.h
View File

@ -178,6 +178,8 @@ void ring_buffer_normalize_time_stamp(struct ring_buffer *buffer,
int cpu, u64 *ts);
void ring_buffer_set_clock(struct ring_buffer *buffer,
u64 (*clock)(void));
void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs);
bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer);
size_t ring_buffer_page_len(void *page);

11
kernel/trace/ring_buffer.c
View File

@ -488,6 +488,7 @@ struct ring_buffer {
u64 (*clock)(void);
struct rb_irq_work irq_work;
bool time_stamp_abs;
};
struct ring_buffer_iter {
@ -1382,6 +1383,16 @@ void ring_buffer_set_clock(struct ring_buffer *buffer,
buffer->clock = clock;
}
void ring_buffer_set_time_stamp_abs(struct ring_buffer *buffer, bool abs)
{
buffer->time_stamp_abs = abs;
}
bool ring_buffer_time_stamp_abs(struct ring_buffer *buffer)
{
return buffer->time_stamp_abs;
}
static void rb_reset_cpu(struct ring_buffer_per_cpu *cpu_buffer);
static inline unsigned long rb_page_entries(struct buffer_page *bpage)

33
kernel/trace/trace.c
View File

@ -2269,7 +2269,7 @@ trace_event_buffer_lock_reserve(struct ring_buffer **current_rb,
*current_rb = trace_file->tr->trace_buffer.buffer;
if ((trace_file->flags &
if (!ring_buffer_time_stamp_abs(*current_rb) && (trace_file->flags &
(EVENT_FILE_FL_SOFT_DISABLED | EVENT_FILE_FL_FILTERED)) &&
(entry = this_cpu_read(trace_buffered_event))) {
/* Try to use the per cpu buffer first */
@ -6282,6 +6282,37 @@ static int tracing_clock_open(struct inode *inode, struct file *file)
return ret;
}
int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs)
{
int ret = 0;
mutex_lock(&trace_types_lock);
if (abs && tr->time_stamp_abs_ref++)
goto out;
if (!abs) {
if (WARN_ON_ONCE(!tr->time_stamp_abs_ref)) {
ret = -EINVAL;
goto out;
}
if (--tr->time_stamp_abs_ref)
goto out;
}
ring_buffer_set_time_stamp_abs(tr->trace_buffer.buffer, abs);
#ifdef CONFIG_TRACER_MAX_TRACE
if (tr->max_buffer.buffer)
ring_buffer_set_time_stamp_abs(tr->max_buffer.buffer, abs);
#endif
out:
mutex_unlock(&trace_types_lock);
return ret;
}
struct ftrace_buffer_info {
struct trace_iterator iter;
void *spare;

3
kernel/trace/trace.h
View File

@ -273,6 +273,7 @@ struct trace_array {
/* function tracing enabled */
int function_enabled;
#endif
int time_stamp_abs_ref;
};
enum {
@ -286,6 +287,8 @@ extern struct mutex trace_types_lock;
extern int trace_array_get(struct trace_array *tr);
extern void trace_array_put(struct trace_array *tr);
extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
/*
* The global tracer (top) should be the first trace array added,
* but we check the flag anyway.