Re: [PATCH] tracing/profile: Fix profile_disable vs module_unload

From: Li Zefan
Date: Mon Aug 24 2009 - 02:23:41 EST

Peter Zijlstra wrote:
> On Mon, 2009-08-24 at 12:19 +0800, Li Zefan wrote:
>> If the correspoding module is unloaded before ftrace_profile_disable()
>> is called, event->profile_disable() won't be called, which can
>> cause oops:
>> # insmod trace-events-sample.ko
>> # perf record -f -a -e sample:foo_bar sleep 3 &
>> # sleep 1
>> # rmmod trace_events_sample
>> # insmod trace-events-sample.ko
>> OOPS!
>> Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
> Hrmm, feel fragile, why don't we check if all a modules tracepoints are
> unused on unload?

I don't think it's fragile. We are profiling via a module's
tracepoint, so we should pin the module, via module_get().
If event->profile_enable() has been calld, we should make
sure it's profile_disable() will be called.

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