Commit dd42cd3e authored by Steven Rostedt (Red Hat)'s avatar Steven Rostedt (Red Hat) Committed by Steven Rostedt
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tracing: Add function probe to trigger stack traces 



Add a function probe that will cause a stack trace to be traced in
the ring buffer when the given function(s) are called.

format is:

 <function>:stacktrace[:<count>]

 echo 'schedule:stacktrace' > /debug/tracing/set_ftrace_filter
 cat /debug/tracing/trace_pipe
     kworker/2:0-4329  [002] ...2  2933.558007: <stack trace>
 => kthread
 => ret_from_fork
          <idle>-0     [000] .N.2  2933.558019: <stack trace>
 => rest_init
 => start_kernel
 => x86_64_start_reservations
 => x86_64_start_kernel
     kworker/2:0-4329  [002] ...2  2933.558109: <stack trace>
 => kthread
 => ret_from_fork
[...]

This can be set to only trace a specific amount of times:

 echo 'schedule:stacktrace:3' > /debug/tracing/set_ftrace_filter
 cat /debug/tracing/trace_pipe
           <...>-58    [003] ...2   841.801694: <stack trace>
 => kthread
 => ret_from_fork
          <idle>-0     [001] .N.2   841.801697: <stack trace>
 => start_secondary
           <...>-2059  [001] ...2   841.801736: <stack trace>
 => wait_for_common
 => wait_for_completion
 => flush_work
 => tty_flush_to_ldisc
 => input_available_p
 => n_tty_poll
 => tty_poll
 => do_select
 => core_sys_select
 => sys_select
 => system_call_fastpath

To remove these:

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

Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent c142be8e

kernel/trace/trace_functions.c

+115 −35
Original line number Diff line number Diff line
@@ -265,56 +265,103 @@ ftrace_traceoff(unsigned long ip, unsigned long parent_ip, void **data) 
	tracing_off();

}



/*

 * Skip 4:

 *   ftrace_stacktrace()

 *   function_trace_probe_call()

 *   ftrace_ops_list_func()

 *   ftrace_call()

 */

#define STACK_SKIP 4



static void

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

{

	trace_dump_stack(STACK_SKIP);

}



static void

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

{

	if (!tracing_is_on())

		return;



	if (update_count(data))

		trace_dump_stack(STACK_SKIP);

}



static int

ftrace_probe_print(const char *name, struct seq_file *m,

		   unsigned long ip, void *data)

{

	long count = (long)data;



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



	if (count == -1)

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

	else

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



	return 0;

}



static int

ftrace_traceon_print(struct seq_file *m, unsigned long ip,

			 struct ftrace_probe_ops *ops, void *data)

{

	return ftrace_probe_print("traceon", m, ip, data);

}



static int

ftrace_traceoff_print(struct seq_file *m, unsigned long ip,

			 struct ftrace_probe_ops *ops, void *data)

{

	return ftrace_probe_print("traceoff", m, ip, data);

}



static int

ftrace_trace_onoff_print(struct seq_file *m, unsigned long ip,

			 struct ftrace_probe_ops *ops, void *data);

ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,

			struct ftrace_probe_ops *ops, void *data)

{

	return ftrace_probe_print("stacktrace", m, ip, data);

}



static struct ftrace_probe_ops traceon_count_probe_ops = {

	.func			= ftrace_traceon_count,

	.print			= ftrace_trace_onoff_print,

	.print			= ftrace_traceon_print,

};



static struct ftrace_probe_ops traceoff_count_probe_ops = {

	.func			= ftrace_traceoff_count,

	.print			= ftrace_trace_onoff_print,

	.print			= ftrace_traceoff_print,

};



static struct ftrace_probe_ops stacktrace_count_probe_ops = {

	.func			= ftrace_stacktrace_count,

	.print			= ftrace_stacktrace_print,

};



static struct ftrace_probe_ops traceon_probe_ops = {

	.func			= ftrace_traceon,

	.print			= ftrace_trace_onoff_print,

	.print			= ftrace_traceon_print,

};



static struct ftrace_probe_ops traceoff_probe_ops = {

	.func			= ftrace_traceoff,

	.print			= ftrace_trace_onoff_print,

	.print			= ftrace_traceoff_print,

};



static int

ftrace_trace_onoff_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);



	if (ops == &traceon_probe_ops || ops == &traceon_count_probe_ops)

		seq_printf(m, "traceon");

	else

		seq_printf(m, "traceoff");



	if (count == -1)

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

	else

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



	return 0;

}

static struct ftrace_probe_ops stacktrace_probe_ops = {

	.func			= ftrace_stacktrace,

	.print			= ftrace_stacktrace_print,

};



static int

ftrace_trace_onoff_callback(struct ftrace_hash *hash,

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

ftrace_trace_probe_callback(struct ftrace_probe_ops *ops,

			    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;
@@ -323,12 +370,6 @@ ftrace_trace_onoff_callback(struct ftrace_hash *hash, 
	if (!enable)

		return -EINVAL;



	/* we register both traceon and traceoff to this callback */

	if (strcmp(cmd, "traceon") == 0)

		ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;

	else

		ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;



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

		unregister_ftrace_function_probe_func(glob+1, ops);

		return 0;
@@ -356,6 +397,34 @@ ftrace_trace_onoff_callback(struct ftrace_hash *hash, 
	return ret < 0 ? ret : 0;

}



static int

ftrace_trace_onoff_callback(struct ftrace_hash *hash,

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

{

	struct ftrace_probe_ops *ops;



	/* we register both traceon and traceoff to this callback */

	if (strcmp(cmd, "traceon") == 0)

		ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;

	else

		ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;



	return ftrace_trace_probe_callback(ops, hash, glob, cmd,

					   param, enable);

}



static int

ftrace_stacktrace_callback(struct ftrace_hash *hash,

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

{

	struct ftrace_probe_ops *ops;



	ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;



	return ftrace_trace_probe_callback(ops, hash, glob, cmd,

					   param, enable);

}



static struct ftrace_func_command ftrace_traceon_cmd = {

	.name			= "traceon",

	.func			= ftrace_trace_onoff_callback,
@@ -366,6 +435,11 @@ static struct ftrace_func_command ftrace_traceoff_cmd = { 
	.func			= ftrace_trace_onoff_callback,

};



static struct ftrace_func_command ftrace_stacktrace_cmd = {

	.name			= "stacktrace",

	.func			= ftrace_stacktrace_callback,

};



static int __init init_func_cmd_traceon(void)

{

	int ret;
@@ -377,6 +451,12 @@ static int __init init_func_cmd_traceon(void) 
	ret = register_ftrace_command(&ftrace_traceon_cmd);

	if (ret)

		unregister_ftrace_command(&ftrace_traceoff_cmd);



	ret = register_ftrace_command(&ftrace_stacktrace_cmd);

	if (ret) {

		unregister_ftrace_command(&ftrace_traceoff_cmd);

		unregister_ftrace_command(&ftrace_traceon_cmd);

	}

	return ret;

}

#else

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