Commit 93e31ffb authored by Tom Zanussi's avatar Tom Zanussi Committed by Steven Rostedt
Browse files

tracing: Add 'snapshot' event trigger command 

Add 'snapshot' event_command.  snapshot event triggers are added by
the user via this command in a similar way and using practically the
same syntax as the analogous 'snapshot' ftrace function command, but
instead of writing to the set_ftrace_filter file, the snapshot event
trigger is written to the per-event 'trigger' files:

    echo 'snapshot' > .../somesys/someevent/trigger

The above command will turn on snapshots for someevent i.e. whenever
someevent is hit, a snapshot will be done.

This also adds a 'count' version that limits the number of times the
command will be invoked:

    echo 'snapshot:N' > .../somesys/someevent/trigger

Where N is the number of times the command will be invoked.

The above command will snapshot N times for someevent i.e. whenever
someevent is hit N times, a snapshot will be done.

Also adds a new tracing_alloc_snapshot() function - the existing
tracing_snapshot_alloc() function is a special version of
tracing_snapshot() that also does the snapshot allocation - the
snapshot triggers would like to be able to do just the allocation but
not take a snapshot; the existing tracing_snapshot_alloc() in turn now
also calls tracing_alloc_snapshot() underneath to do that allocation.

Link: http://lkml.kernel.org/r/c9524dd07ce01f9dcbd59011290e0a8d5b47d7ad.1382622043.git.tom.zanussi@linux.intel.com



Signed-off-by: default avatarTom Zanussi <tom.zanussi@linux.intel.com>
[ fix up from kbuild test robot <fengguang.wu@intel.com report ]
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 2a2df321

include/linux/ftrace_event.h

+1 −0
Original line number Diff line number Diff line
@@ -346,6 +346,7 @@ struct ftrace_event_file { 
enum event_trigger_type {

	ETT_NONE		= (0),

	ETT_TRACE_ONOFF		= (1 << 0),

	ETT_SNAPSHOT		= (1 << 1),

};



extern void destroy_preds(struct ftrace_event_file *file);

kernel/trace/trace.c

+30 −3
Original line number Diff line number Diff line
@@ -594,6 +594,28 @@ void free_snapshot(struct trace_array *tr) 
	tr->allocated_snapshot = false;

}



/**

 * tracing_alloc_snapshot - allocate snapshot buffer.

 *

 * This only allocates the snapshot buffer if it isn't already

 * allocated - it doesn't also take a snapshot.

 *

 * This is meant to be used in cases where the snapshot buffer needs

 * to be set up for events that can't sleep but need to be able to

 * trigger a snapshot.

 */

int tracing_alloc_snapshot(void)

{

	struct trace_array *tr = &global_trace;

	int ret;



	ret = alloc_snapshot(tr);

	WARN_ON(ret < 0);



	return ret;

}

EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);



/**

 * trace_snapshot_alloc - allocate and take a snapshot of the current buffer.

 *
@@ -607,11 +629,10 @@ void free_snapshot(struct trace_array *tr) 
 */

void tracing_snapshot_alloc(void)

{

	struct trace_array *tr = &global_trace;

	int ret;



	ret = alloc_snapshot(tr);

	if (WARN_ON(ret < 0))

	ret = tracing_alloc_snapshot();

	if (ret < 0)

		return;



	tracing_snapshot();
@@ -623,6 +644,12 @@ void tracing_snapshot(void) 
	WARN_ONCE(1, "Snapshot feature not enabled, but internal snapshot used");

}

EXPORT_SYMBOL_GPL(tracing_snapshot);

int tracing_alloc_snapshot(void)

{

	WARN_ONCE(1, "Snapshot feature not enabled, but snapshot allocation used");

	return -ENODEV;

}

EXPORT_SYMBOL_GPL(tracing_alloc_snapshot);

void tracing_snapshot_alloc(void)

{

	/* Give warning */

kernel/trace/trace.h

+1 −0
Original line number Diff line number Diff line
@@ -1211,6 +1211,7 @@ struct event_command { 


extern int trace_event_enable_disable(struct ftrace_event_file *file,

				      int enable, int soft_disable);

extern int tracing_alloc_snapshot(void);



extern const char *__start___trace_bprintk_fmt[];

extern const char *__stop___trace_bprintk_fmt[];

kernel/trace/trace_events_trigger.c

+85 −0
Original line number Diff line number Diff line
@@ -696,6 +696,90 @@ static struct event_command trigger_traceoff_cmd = { 
	.get_trigger_ops	= onoff_get_trigger_ops,

};



#ifdef CONFIG_TRACER_SNAPSHOT

static void

snapshot_trigger(struct event_trigger_data *data)

{

	tracing_snapshot();

}



static void

snapshot_count_trigger(struct event_trigger_data *data)

{

	if (!data->count)

		return;



	if (data->count != -1)

		(data->count)--;



	snapshot_trigger(data);

}



static int

register_snapshot_trigger(char *glob, struct event_trigger_ops *ops,

			  struct event_trigger_data *data,

			  struct ftrace_event_file *file)

{

	int ret = register_trigger(glob, ops, data, file);



	if (ret > 0 && tracing_alloc_snapshot() != 0) {

		unregister_trigger(glob, ops, data, file);

		ret = 0;

	}



	return ret;

}



static int

snapshot_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,

		       struct event_trigger_data *data)

{

	return event_trigger_print("snapshot", m, (void *)data->count,

				   data->filter_str);

}



static struct event_trigger_ops snapshot_trigger_ops = {

	.func			= snapshot_trigger,

	.print			= snapshot_trigger_print,

	.init			= event_trigger_init,

	.free			= event_trigger_free,

};



static struct event_trigger_ops snapshot_count_trigger_ops = {

	.func			= snapshot_count_trigger,

	.print			= snapshot_trigger_print,

	.init			= event_trigger_init,

	.free			= event_trigger_free,

};



static struct event_trigger_ops *

snapshot_get_trigger_ops(char *cmd, char *param)

{

	return param ? &snapshot_count_trigger_ops : &snapshot_trigger_ops;

}



static struct event_command trigger_snapshot_cmd = {

	.name			= "snapshot",

	.trigger_type		= ETT_SNAPSHOT,

	.func			= event_trigger_callback,

	.reg			= register_snapshot_trigger,

	.unreg			= unregister_trigger,

	.get_trigger_ops	= snapshot_get_trigger_ops,

};



static __init int register_trigger_snapshot_cmd(void)

{

	int ret;



	ret = register_event_command(&trigger_snapshot_cmd);

	WARN_ON(ret < 0);



	return ret;

}

#else

static __init int register_trigger_snapshot_cmd(void) { return 0; }

#endif /* CONFIG_TRACER_SNAPSHOT */



static __init void unregister_trigger_traceon_traceoff_cmds(void)

{

	unregister_event_command(&trigger_traceon_cmd);
@@ -719,6 +803,7 @@ static __init int register_trigger_traceon_traceoff_cmds(void) 
__init int register_trigger_cmds(void)

{

	register_trigger_traceon_traceoff_cmds();

	register_trigger_snapshot_cmd();



	return 0;

}

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