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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: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Masami Hiramatsu 2013-05-09 14:44:29 +09:00 committed by Steven Rostedt
parent 30052170dc
commit 1cf4c0732d
2 changed files with 11 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/ftrace_event.h
View File

@ -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) \

12
kernel/trace/trace_events.c
View File

@ -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;