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
......@@ -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);
......
......@@ -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 */
......
......@@ -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[];
......
......@@ -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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