linux-kernel - Re: [PATCH v4] lockdep: check that no locks held at freeze time

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Message-Id: <20130220152446.a65ff84f.akpm@linux-foundation.org>
Date:	Wed, 20 Feb 2013 15:24:46 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mandeep Singh Baines <msb@...omium.org>
Cc:	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Tejun Heo <tj@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH v4] lockdep: check that no locks held at freeze time

On Wed, 20 Feb 2013 15:17:16 -0800
Mandeep Singh Baines <msb@...omium.org> wrote:

> We shouldn't try_to_freeze if locks are held.
> 
> ...
>
> @@ -43,6 +44,9 @@ extern void thaw_kernel_threads(void);
>  
> +	if (!(current->flags & PF_NOFREEZE))
> +		debug_check_no_locks_held(current,
> +
>					  "lock held while trying to freeze");
> ...
>
> +	debug_check_no_locks_held(tsk, "lock held at task exit time");

There doesn't seem much point in adding the `msg' to
debug_check_no_locks_held() - the dump_stack() in
print_held_locks_bug() will tell us the same thing.  Maybe just change
the print_held_locks_bug() messages so they stop assuming they were
called from do_exit()?

Also, I wonder if the `tsk' arg is needed.  In both callers
tsk==current.  Is it likely that we'll ever call
debug_check_no_locks_held() for any task other than `current'?

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