From: Pavel Machek <pavel@ucw.cz>
To: Colin Cross <ccross@android.com>
Cc: linux-kernel@vger.kernel.org, "Rafael J. Wysocki" <rjw@sisk.pl>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Mandeep Singh Baines <msb@chromium.org>,
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>,
Tejun Heo <tj@kernel.org>, Len Brown <len.brown@intel.com>
Subject: Re: [PATCH v3 02/16] freezer: add unsafe versions of freezable helpers for CIFS
Date: Tue, 7 May 2013 14:28:04 +0200 [thread overview]
Message-ID: <20130507122803.GA2585@elf.ucw.cz> (raw)
In-Reply-To: <1367884221-20462-3-git-send-email-ccross@android.com>
On Mon 2013-05-06 16:50:07, Colin Cross wrote:
> CIFS calls wait_event_freezekillable_unsafe with a VFS lock held,
> which is unsafe and will cause lockdep warnings when 6aa9707
> "lockdep: check that no locks held at freeze time" is reapplied
> (it was reverted in dbf520a). CIFS shouldn't be doing this, but
> it has long-running syscalls that must hold a lock but also
> shouldn't block suspend. Until CIFS freeze handling is rewritten
> to use a signal to exit out of the critical section, add a new
> wait_event_freezekillable_unsafe helper that will not run the
> lockdep test when 6aa9707 is reapplied, and call it from CIFS.
>
> In practice the likley result of holding the lock while freezing
> is that a second task blocked on the lock will never freeze,
> aborting suspend, but it is possible to manufacture a case using
> the cgroup freezer, the lock, and the suspend freezer to create
> a deadlock. Silencing the lockdep warning here will allow
> problems to be found in other drivers that may have a more
> serious deadlock risk, and prevent new problems from being added.
>
> Signed-off-by: Colin Cross <ccross@android.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2013-05-07 12:28 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-06 23:50 [PATCH v2 00/10] optimize freezing tasks by reducing task wakeups Colin Cross
2013-05-06 23:50 ` [PATCH v3 01/16] freezer: add unsafe versions of freezable helpers for NFS Colin Cross
2013-05-06 23:50 ` [PATCH v3 02/16] freezer: add unsafe versions of freezable helpers for CIFS Colin Cross
2013-05-07 10:07 ` Jeff Layton
2013-05-07 17:47 ` Colin Cross
2013-05-07 17:52 ` [PATCH v4 " Colin Cross
2013-05-07 18:11 ` Jeff Layton
2013-05-07 12:28 ` Pavel Machek [this message]
2013-05-06 23:50 ` [PATCH v3 03/16] lockdep: remove task argument from debug_check_no_locks_held Colin Cross
2013-05-07 12:28 ` Pavel Machek
2013-05-06 23:50 ` [PATCH v3 04/16] lockdep: check that no locks held at freeze time Colin Cross
2013-05-07 12:29 ` Pavel Machek
2013-05-06 23:50 ` [PATCH v3 05/16] freezer: shorten freezer sleep time using exponential backoff Colin Cross
2013-05-06 23:50 ` [PATCH v3 06/16] freezer: skip waking up tasks with PF_FREEZER_SKIP set Colin Cross
2013-05-06 23:50 ` [PATCH v3 07/16] freezer: convert freezable helpers to freezer_do_not_count() Colin Cross
2013-05-06 23:50 ` [PATCH v3 08/16] freezer: convert freezable helpers to static inline where possible Colin Cross
2013-05-06 23:50 ` [PATCH v3 09/16] freezer: add new freezable helpers using freezer_do_not_count() Colin Cross
2013-05-06 23:50 ` [PATCH v3 10/16] binder: use freezable blocking calls Colin Cross
2013-05-06 23:50 ` [PATCH v3 11/16] epoll: use freezable blocking call Colin Cross
2013-05-06 23:50 ` [PATCH v3 12/16] select: " Colin Cross
2013-05-06 23:50 ` [PATCH v3 13/16] futex: " Colin Cross
2013-07-22 23:02 ` 3.11-rc regression bisected: s2disk does not work (was Re: [PATCH v3 13/16] futex: use freezable blocking call) Michael Leun
2013-07-22 23:55 ` Colin Cross
2013-07-23 0:32 ` Linus Torvalds
2013-07-23 0:42 ` Colin Cross
2013-07-23 1:41 ` Rafael J. Wysocki
2013-07-23 6:28 ` Colin Cross
2013-07-23 20:31 ` Colin Cross
2013-07-23 21:58 ` Michael Leun
2013-07-23 18:08 ` Michael Leun
2013-07-23 18:24 ` Darren Hart
2013-07-23 18:29 ` Colin Cross
2013-07-23 19:16 ` Michael Leun
2013-07-23 19:29 ` Colin Cross
2013-07-23 19:58 ` Michael Leun
2013-07-23 21:43 ` Rafael J. Wysocki
2013-07-23 0:26 ` Pavel Machek
2013-05-06 23:50 ` [PATCH v3 14/16] nanosleep: use freezable blocking call Colin Cross
2013-05-06 23:50 ` [PATCH v3 15/16] sigtimedwait: " Colin Cross
2013-05-06 23:50 ` [PATCH v3 16/16] af_unix: use freezable blocking calls in read Colin Cross
2013-05-07 18:12 ` [PATCH v2 00/10] optimize freezing tasks by reducing task wakeups Tejun Heo
2013-05-08 0:02 ` Rafael J. Wysocki
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