From: Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH v2 07/17] debugobjects: Move printk out of db lock
	critical sections
Date: Fri, 7 Dec 2018 10:21:56 +0100
Message-ID: <20181207092156.GE2237@hirez.programming.kicks-ass.net>
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To: Waiman Long <longman-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Petr Mladek <pmladek-IBi9RG/b67k@public.gmane.org>, Sergey Senozhatsky <sergey.senozhatsky-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kasan-dev-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Andrey Ryabinin <aryabinin-5HdwGun5lf+gSpxsJD1C4w@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
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On Mon, Nov 19, 2018 at 01:55:16PM -0500, Waiman Long wrote:
> The db->lock is a raw spinlock and so the lock hold time is supposed
> to be short. This will not be the case when printk() is being involved
> in some of the critical sections. In order to avoid the long hold time,
> in case some messages need to be printed, the debug_object_is_on_stack()
> and debug_print_object() calls are now moved out of those critical
> sections.

That's not why you did this patch though; you want to make these locks
terminal locks and that means no printk() inside, as that uses locks
again.

Please write relevant changelogs.