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Commit 1cf4c073 authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Steven Rostedt
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tracing: Modify soft-mode only if there's no other referrer 

Modify soft-mode flag only if no other soft-mode referrer
(currently only the ftrace triggers) by using a reference
counter in each ftrace_event_file.

Without this fix, adding and removing several different
enable/disable_event triggers on the same event clear
soft-mode bit from the ftrace_event_file. This also
happens with a typo of glob on setting triggers.

e.g.

 # echo vfs_symlink:enable_event:net:netif_rx > set_ftrace_filter
 # cat events/net/netif_rx/enable
 0*
 # echo typo_func:enable_event:net:netif_rx > set_ftrace_filter
 # cat events/net/netif_rx/enable
 0
 # cat set_ftrace_filter
 #### all functions enabled ####
 vfs_symlink:enable_event:net:netif_rx:unlimited

As above, we still have a trigger, but soft-mode is gone.

Link: http://lkml.kernel.org/r/20130509054429.30398.7464.stgit@mhiramat-M0-7522



Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 30052170

include/linux/ftrace_event.h

+1 −0
Original line number Diff line number Diff line
@@ -293,6 +293,7 @@ struct ftrace_event_file { 
	 * caching and such. Which is mostly OK ;-)

	 */

	unsigned long		flags;

	atomic_t		sm_ref;	/* soft-mode reference counter */

};



#define __TRACE_EVENT_FLAGS(name, value)				\

kernel/trace/trace_events.c

+10 −2
Original line number Diff line number Diff line
@@ -251,7 +251,8 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, 
	switch (enable) {

	case 0:

		/*

		 * When soft_disable is set and enable is cleared, we want

		 * When soft_disable is set and enable is cleared, the sm_ref

		 * reference counter is decremented. If it reaches 0, we want

		 * to clear the SOFT_DISABLED flag but leave the event in the

		 * state that it was. That is, if the event was enabled and

		 * SOFT_DISABLED isn't set, then do nothing. But if SOFT_DISABLED
@@ -263,6 +264,8 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, 
		 * "soft enable"s (clearing the SOFT_DISABLED bit) wont work.

		 */

		if (soft_disable) {

			if (atomic_dec_return(&file->sm_ref) > 0)

				break;

			disable = file->flags & FTRACE_EVENT_FL_SOFT_DISABLED;

			clear_bit(FTRACE_EVENT_FL_SOFT_MODE_BIT, &file->flags);

		} else
@@ -291,8 +294,11 @@ static int __ftrace_event_enable_disable(struct ftrace_event_file *file, 
		 */

		if (!soft_disable)

			clear_bit(FTRACE_EVENT_FL_SOFT_DISABLED_BIT, &file->flags);

		else

		else {

			if (atomic_inc_return(&file->sm_ref) > 1)

				break;

			set_bit(FTRACE_EVENT_FL_SOFT_MODE_BIT, &file->flags);

		}



		if (!(file->flags & FTRACE_EVENT_FL_ENABLED)) {
@@ -1540,6 +1546,7 @@ __trace_add_new_event(struct ftrace_event_call *call, 


	file->event_call = call;

	file->tr = tr;

	atomic_set(&file->sm_ref, 0);

	list_add(&file->list, &tr->events);



	return event_create_dir(tr->event_dir, file, id, enable, filter, format);
@@ -1562,6 +1569,7 @@ __trace_early_add_new_event(struct ftrace_event_call *call, 


	file->event_call = call;

	file->tr = tr;

	atomic_set(&file->sm_ref, 0);

	list_add(&file->list, &tr->events);



	return 0;