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

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Date:	Thu, 21 Feb 2013 13:42:27 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mandeep Singh Baines <msb@...omium.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, 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
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