linux-kernel - Re: [PATCH 2/5] lockdep: check that no locks held at freeze time

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Message-ID: <20130215154449.GD30829@redhat.com>
Date:	Fri, 15 Feb 2013 16:44:49 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH 2/5] lockdep: check that no locks held at freeze time

On 02/14, Mandeep Singh Baines wrote:
>
> We shouldn't try_to_freeze if locks are held. Verified that
> I get no lockdep warnings after applying this patch and
> "vfork: don't freezer_count() for in-kernel users of CLONE_VFORK".

Ah. Now I understand why you did 1/5. Beacuse you call
debug_check_no_locks_held() right at the start of try_to_freeze(),
even if the caller can't be frozen.

>  static inline bool try_to_freeze(void)
>  {
> +	debug_check_no_locks_held(current);
>  	might_sleep();
>  	if (likely(!freezing(current)))
>  		return false;

Up to maintainers, but perhaps you should check !PF_NOFREEZE at least?

Oleg.

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