linux-kernel - Re: [PATCH v6] lockdep: check that no locks held at freeze time

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Date:	Thu, 21 Feb 2013 13:57:35 -0800
From:	Mandeep Singh Baines <msb@...omium.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH v6] lockdep: check that no locks held at freeze time

On Thu, Feb 21, 2013 at 1:42 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 21 Feb 2013 08:51:41 -0800
> Mandeep Singh Baines <msb@...omium.org> wrote:
>
>> 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.
>>
>> ...
>>
>> --- a/include/linux/freezer.h
>> +++ b/include/linux/freezer.h
>>
>> ...
>>
>> @@ -43,6 +44,8 @@ extern void thaw_kernel_threads(void);
>>
>>  static inline bool try_to_freeze(void)
>>  {
>> +     if (!(current->flags & PF_NOFREEZE))
>> +             debug_check_no_locks_held();
>>       might_sleep();
>>       if (likely(!freezing(current)))
>>               return false;
>>
>> ...
>>
>
> It still needs
> http://ozlabs.org/~akpm/mmots/broken-out/lockdep-check-that-no-locks-held-at-freeze-time-fix.patch

D'oh. I tricked myself into thinking its part of freezer so no export
needed but its inlined so can be pulled in anywhere.

Thanks for the fix:

Acked-by: Mandeep Singh Baines <msb@...omium.org>

Or should I roll in the fix and re-send with your Sign-off.

Regards,
Mandeep
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