Re: [PATCH v3 04/16] lockdep: check that no locks held at freeze time

From: Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>
To: Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	"Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public.gmane.org>,
	Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Mandeep Singh Baines
	<msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Ben Chan <benchan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Len Brown <len.brown-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v3 04/16] lockdep: check that no locks held at freeze time
Date: Tue, 7 May 2013 14:29:07 +0200	[thread overview]
Message-ID: <20130507122906.GC2585@elf.ucw.cz> (raw)
In-Reply-To: <1367884221-20462-5-git-send-email-ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>

On Mon 2013-05-06 16:50:09, Colin Cross wrote:
> From: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> 
> We shouldn't try_to_freeze if locks are held.  Holding a lock can cause a
> deadlock if the lock is later acquired in the suspend or hibernate path
> (e.g.  by dpm).  Holding a lock can also cause a deadlock in the case of
> cgroup_freezer if a lock is held inside a frozen cgroup that is later
> acquired by a process outside that group.
> 
> History:
> This patch was originally applied as 6aa9707099c and reverted in
> dbf520a9d7d4 because NFS was freezing with locks held.  It was
> deemed better to keep the bad freeze point in NFS to allow laptops
> to suspend consistently.  The previous patch in this series converts
> NFS to call _unsafe versions of the freezable helpers so that
> lockdep doesn't complain about them until a more correct fix
> can be applied.
> 
> [akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org: export debug_check_no_locks_held]
> Signed-off-by: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Cc: Ben Chan <benchan-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
> Cc: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Rafael J. Wysocki <rjw-KKrjLPT3xs0@public.gmane.org>
> Cc: Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Signed-off-by: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> Signed-off-by: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> [ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org: don't warn if try_to_freeze_unsafe is called]
> Signed-off-by: Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>

Acked-by: Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>

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