From: Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
To: Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: lkml <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Pavel Machek <pavel-+ZI9xUNit7I@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 <linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Linux PM list <linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
netdev <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>,
Len Brown <len.brown-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v3 02/16] freezer: add unsafe versions of freezable helpers for CIFS
Date: Tue, 7 May 2013 10:47:36 -0700 [thread overview]
Message-ID: <CAMbhsRQ1i_dFctwjkqjg3=GJdEc8ReEDk=NnEFEXj8u3MaEqDA@mail.gmail.com> (raw)
In-Reply-To: <20130507060730.03364687-9yPaYZwiELC+kQycOl6kW4xkIHaj4LzF@public.gmane.org>
On Tue, May 7, 2013 at 3:07 AM, Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> On Mon, 6 May 2013 16:50:07 -0700
> Colin Cross <ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org> 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-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
>> ---
>> include/linux/freezer.h | 13 +++++++++++++
>> 1 file changed, 13 insertions(+)
>>
>> diff --git a/include/linux/freezer.h b/include/linux/freezer.h
>> index 5b31e21c..d3c038e 100644
>> --- a/include/linux/freezer.h
>> +++ b/include/linux/freezer.h
>> @@ -212,6 +212,16 @@ static inline bool freezer_should_skip(struct task_struct *p)
>> __retval; \
>> })
>>
>> +/* DO NOT ADD ANY NEW CALLERS OF THIS FUNCTION */
>> +#define wait_event_freezekillable_unsafe(wq, condition) \
>> +({ \
>> + int __retval; \
>> + freezer_do_not_count(); \
>> + __retval = wait_event_killable(wq, (condition)); \
>> + freezer_count_unsafe(); \
>> + __retval; \
>> +})
>> +
>> #define wait_event_freezable(wq, condition) \
>> ({ \
>> int __retval; \
>> @@ -277,6 +287,9 @@ static inline void set_freezable(void) {}
>> #define wait_event_freezekillable(wq, condition) \
>> wait_event_killable(wq, condition)
>>
>> +#define wait_event_freezekillable_unsafe(wq, condition) \
>> + wait_event_killable(wq, condition)
>> +
>> #endif /* !CONFIG_FREEZER */
>>
>> #endif /* FREEZER_H_INCLUDED */
>
> I think you also need to convert wait_for_response in the cifs code to
> use this helper. While it's a pretty straightforward change, you should
> probably cc linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org as well.
>
> --
> Jeff Layton <jlayton-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Oops, dropped a hunk which is why linux-cifs didn't get cc'd. I will resend it.
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next prev parent reply other threads:[~2013-05-07 17:47 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
[not found] ` <20130507060730.03364687-9yPaYZwiELC+kQycOl6kW4xkIHaj4LzF@public.gmane.org>
2013-05-07 17:47 ` Colin Cross [this message]
[not found] ` <CAMbhsRQ1i_dFctwjkqjg3=GJdEc8ReEDk=NnEFEXj8u3MaEqDA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-05-07 17:52 ` [PATCH v4 " Colin Cross
[not found] ` <1367949125-21809-1-git-send-email-ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
2013-05-07 18:11 ` Jeff Layton
[not found] ` <1367884221-20462-3-git-send-email-ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
2013-05-07 12:28 ` [PATCH v3 " Pavel Machek
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
[not found] ` <1367884221-20462-5-git-send-email-ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
2013-05-07 12:29 ` Pavel Machek
[not found] ` <1367884221-20462-1-git-send-email-ccross-z5hGa2qSFaRBDgjK7y7TUQ@public.gmane.org>
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
[not found] ` <CA+55aFzUVPJe96z8V0F-znc8ZcpJid7LEeYww80M-Mx=S91tAA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-23 0:42 ` Colin Cross
[not found] ` <CAMbhsRReF9xB597i9CcCj7D1P5kvB4cc0JmDQYeboqi11Kp99A-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-23 1:41 ` Rafael J. Wysocki
[not found] ` <15305281.aClQ8XUG9t-sKB8Sp2ER+y1GS7QM15AGw@public.gmane.org>
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
[not found] ` <20130723211622.50f75087-gjVD6BTPoEbYa4IuQwzu8g@public.gmane.org>
2013-07-23 19:29 ` Colin Cross
[not found] ` <CAMbhsRQU=TswYg-2WqHmzt-_GpfMFpYHPSU4eFd5XMw7DRGXJA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-23 19:58 ` Michael Leun
[not found] ` <CAMbhsRT6zOKLhG_uh=nA8H_3d7afhG+4jvWjvidY3fEguryP_Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2013-07-23 21:43 ` Rafael J. Wysocki
[not found] ` <20130723010250.5a3465ec-gjVD6BTPoEbYa4IuQwzu8g@public.gmane.org>
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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