Date: Mon, 6 May 2013 12:01:15 -0700
From: Tejun Heo <tj@kernel.org>
To: Colin Cross <ccross@android.com>
Cc: linux-kernel@vger.kernel.org, Trond Myklebust <Trond.Myklebust@netapp.com>,
        Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
        "Rafael J. Wysocki" <rjw@sisk.pl>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        "David S. Miller" <davem@davemloft.net>,
        Andrew Morton <akpm@linux-foundation.org>,
        Mandeep Singh Baines <msb@chromium.org>,
        Paul Walmsley <paul@pwsan.com>, Al Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Oleg Nesterov <oleg@redhat.com>, linux-nfs@vger.kernel.org,
        linux-pm@vger.kernel.org, netdev@vger.kernel.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ben Chan <benchan@chromium.org>
Subject: Re: [PATCH 2/2] lockdep: check that no locks held at freeze time
Message-ID: <20130506190115.GB800@mtj.dyndns.org>
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On Fri, May 03, 2013 at 02:04:10PM -0700, Colin Cross wrote:
> From: Mandeep Singh Baines <msb@chromium.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.

I don't care about %current change, especially given that it's a debug
interface but that really should be a separate patch, so please split
it out if you want it (and I think we want it).

Thanks.

-- 
tejun