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Commit 77fd5c15 authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add snapshot trigger to function probes 



 echo 'schedule:snapshot:1' > /debug/tracing/set_ftrace_filter

This will cause the scheduler to trigger a snapshot the next time
it's called (you can use any function that's not called by NMI).

Even though it triggers only once, you still need to remove it with:

 echo '!schedule:snapshot:0' > /debug/tracing/set_ftrace_filter

The :1 can be left off for the first command:

 echo 'schedule:snapshot' > /debug/tracing/set_ftrace_filter

But this will cause all calls to schedule to trigger a snapshot.
This must be removed without the ':0'

 echo '!schedule:snapshot' > /debug/tracing/set_ftrace_filter

As adding a "count" is a different operation (internally).

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 3209cff4

kernel/trace/trace.c

+110 −1
Original line number Diff line number Diff line
@@ -5086,7 +5086,114 @@ static const struct file_operations tracing_dyn_info_fops = { 
	.read		= tracing_read_dyn_info,

	.llseek		= generic_file_llseek,

};

#endif

#endif /* CONFIG_DYNAMIC_FTRACE */



#if defined(CONFIG_TRACER_SNAPSHOT) && defined(CONFIG_DYNAMIC_FTRACE)

static void

ftrace_snapshot(unsigned long ip, unsigned long parent_ip, void **data)

{

	tracing_snapshot();

}



static void

ftrace_count_snapshot(unsigned long ip, unsigned long parent_ip, void **data)

{

	unsigned long *count = (long *)data;



	if (!*count)

		return;



	if (*count != -1)

		(*count)--;



	tracing_snapshot();

}



static int

ftrace_snapshot_print(struct seq_file *m, unsigned long ip,

		      struct ftrace_probe_ops *ops, void *data)

{

	long count = (long)data;



	seq_printf(m, "%ps:", (void *)ip);



	seq_printf(m, "snapshot");



	if (count == -1)

		seq_printf(m, ":unlimited\n");

	else

		seq_printf(m, ":count=%ld\n", count);



	return 0;

}



static struct ftrace_probe_ops snapshot_probe_ops = {

	.func			= ftrace_snapshot,

	.print			= ftrace_snapshot_print,

};



static struct ftrace_probe_ops snapshot_count_probe_ops = {

	.func			= ftrace_count_snapshot,

	.print			= ftrace_snapshot_print,

};



static int

ftrace_trace_snapshot_callback(struct ftrace_hash *hash,

			       char *glob, char *cmd, char *param, int enable)

{

	struct ftrace_probe_ops *ops;

	void *count = (void *)-1;

	char *number;

	int ret;



	/* hash funcs only work with set_ftrace_filter */

	if (!enable)

		return -EINVAL;



	ops = param ? &snapshot_count_probe_ops :  &snapshot_probe_ops;



	if (glob[0] == '!') {

		unregister_ftrace_function_probe_func(glob+1, ops);

		return 0;

	}



	if (!param)

		goto out_reg;



	number = strsep(&param, ":");



	if (!strlen(number))

		goto out_reg;



	/*

	 * We use the callback data field (which is a pointer)

	 * as our counter.

	 */

	ret = kstrtoul(number, 0, (unsigned long *)&count);

	if (ret)

		return ret;



 out_reg:

	ret = register_ftrace_function_probe(glob, ops, count);



	if (ret >= 0)

		alloc_snapshot(&global_trace);



	return ret < 0 ? ret : 0;

}



static struct ftrace_func_command ftrace_snapshot_cmd = {

	.name			= "snapshot",

	.func			= ftrace_trace_snapshot_callback,

};



static int register_snapshot_cmd(void)

{

	return register_ftrace_command(&ftrace_snapshot_cmd);

}

#else

static inline int register_snapshot_cmd(void) { return 0; }

#endif /* defined(CONFIG_TRACER_SNAPSHOT) && defined(CONFIG_DYNAMIC_FTRACE) */



struct dentry *tracing_init_dentry_tr(struct trace_array *tr)

{
@@ -6076,6 +6183,8 @@ __init static int tracer_alloc_buffers(void) 
		trace_set_options(&global_trace, option);

	}



	register_snapshot_cmd();



	return 0;



out_free_cpumask: