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Date: Wed, 24 Sep 2014 10:36:38 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, oleg@redhat.com, torvalds@linux-foundation.org
Cc: tglx@linutronix.de, ilya.dryomov@inktank.com, umgwanakikbuti@gmail.com,
        linux-kernel@vger.kernel.org, David Miller <davem@davemloft.net>
Subject: Re: [PATCH 09/11] net: Clean up sk_wait_event() vs might_sleep()
Message-ID: <20140924083638.GV16043@twins.programming.kicks-ass.net>
References: <20140924081845.572814794@infradead.org>
 <20140924082242.524407432@infradead.org>
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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@vger.kernel.org
> Cc: David Miller <davem@davemloft.net>
> Reported-by: Ilya Dryomov <ilya.dryomov@inktank.com>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

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

 lkml.kernel.org/r/20140924082242.186408915@infradead.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;							\
> 
>