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tracing: Return -EBUSY when event_enable_func() fails to get module 

Since try_module_get() returns false( = 0) when it fails to
pindown a module, event_enable_func() returns 0 which means
"succeed". This can cause a kernel panic when the entry
is removed, because the event is already released.

This fixes the bug by returning -EBUSY, because the reason
why it fails is that the module is being removed at that time.

Link: http://lkml.kernel.org/r/20130516114848.13508.97899.stgit@mhiramat-M0-7522

Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Tom Zanussi <tom.zanussi@intel.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.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 2013-05-16 20:48:49 +09:00 committed by Steven Rostedt
parent b62fdd97fc
commit 6ed0106667
1 changed files with 3 additions and 1 deletions
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4
kernel/trace/trace_events.c
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@ -2072,8 +2072,10 @@ event_enable_func(struct ftrace_hash *hash,
out_reg:
/* Don't let event modules unload while probe registered */
ret = try_module_get(file->event_call->mod);
if (!ret)
if (!ret) {
ret = -EBUSY;
goto out_free;
}
ret = __ftrace_event_enable_disable(file, 1, 1);
if (ret < 0)