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authorMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>2013-05-09 14:44:29 +0900
committerSteven Rostedt <rostedt@goodmis.org>2013-05-09 20:14:25 -0400
commit1cf4c0732db3cd3c49cadbc60ff6bda08604e6fa (patch)
tree74133737a3ecea18847788c10fae7bb474f1aaa8 /kernel
parent30052170dcc256c18a43fb3e76577a67394543f8 (diff)
downloadlinux-1cf4c0732db3cd3c49cadbc60ff6bda08604e6fa.tar.gz
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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/trace/trace_events.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 915c136d7bd..8be1224046f 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -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;