From mboxrd@z Thu Jan  1 00:00:00 1970
From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH] locking/lockdep: Save and display stack trace of held
 locks
Date: Mon, 24 Jun 2019 13:08:52 +0200
Message-ID: <20190624110852.GV3419@hirez.programming.kicks-ass.net>
References: <1561363259-14705-1-git-send-email-kobe-cp.wu@mediatek.com>
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To: Kobe Wu <kobe-cp.wu-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
Cc: linux-mediatek-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>, wsd_upstream-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org, Eason Lin <eason-yh.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>
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On Mon, Jun 24, 2019 at 04:00:59PM +0800, Kobe Wu wrote:
> Save the stack trace of held locks when lock_acquire() is invoked
> and display the stack trace when lockdep_print_held_locks() is
> invoked. The runtime stack trace of held locks are helpful in
> analyzing code flow and lockdep's warning.
> 
> Save stack trace of each held lock will increase runtime overhead
> and memory consumption. The operation will be activated under
> CONFIG_LOCKDEP_TRACE_HELD_LOCK. So the impact will only occur
> when CONFIG_LOCKDEP_TRACE_HELD_LOCK=y.

Yeah, I don't see the point of this. If you cannot find where the lock
got taken you've bigger problems.