linux-kernel - Re: [PATCH 09/11] net: Clean up sk_wait_event() vs might

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Date:	Wed, 24 Sep 2014 10:36:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	mingo@...nel.org, oleg@...hat.com, torvalds@...ux-foundation.org
Cc:	tglx@...utronix.de, ilya.dryomov@...tank.com,
	umgwanakikbuti@...il.com, linux-kernel@...r.kernel.org,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH 09/11] net: Clean up sk_wait_event() vs might_sleep()

On Wed, Sep 24, 2014 at 10:18:54AM +0200, Peter Zijlstra wrote:
> WARNING: CPU: 1 PID: 1744 at kernel/sched/core.c:7104 __might_sleep+0x58/0x90()
> do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff81070e10>] prepare_to_wait+0x50 /0xa0
> 
>  [<ffffffff8105bc38>] __might_sleep+0x58/0x90
>  [<ffffffff8148c671>] lock_sock_nested+0x31/0xb0
>  [<ffffffff81498aaa>] sk_stream_wait_memory+0x18a/0x2d0
> 
> Which is a false positive because sk_wait_event() will already have
> TASK_RUNNING at that point if it would've gone through
> schedule_timeout().
> 
> So annotate with fixup_sleep(); which goes away on !DEBUG builds.
> 
> Cc: netdev@...r.kernel.org
> Cc: David Miller <davem@...emloft.net>
> Reported-by: Ilya Dryomov <ilya.dryomov@...tank.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Dave, FYI this patch relies on a previous one that introduces the
fixup_sleep()

 lkml.kernel.org/r/20140924082242.186408915@...radead.org

If you're ok with things, I'll merge this one along with the rest of
things.

> ---
>  include/net/sock.h |    1 +
>  1 file changed, 1 insertion(+)
> 
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -902,6 +902,7 @@ static inline void sock_rps_reset_rxhash
>  		if (!__rc) {						\
>  			*(__timeo) = schedule_timeout(*(__timeo));	\
>  		}							\
> +		fixup_sleep();						\
>  		lock_sock(__sk);					\
>  		__rc = __condition;					\
>  		__rc;							\
> 
> 
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