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From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>,
	Davidlohr Bueso <dave@stgolabs.net>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched: Fix data-race in wakeup
Date: Tue, 17 Nov 2020 12:40:00 +0000	[thread overview]
Message-ID: <20201117124000.GY3371@techsingularity.net> (raw)
In-Reply-To: <20201117083016.GK3121392@hirez.programming.kicks-ass.net>

On Tue, Nov 17, 2020 at 09:30:16AM +0100, Peter Zijlstra wrote:
> > sched_psi_wake_requeue can probably stay with the other three fields
> > given they are under the rq lock but sched_remote_wakeup needs to move
> > out.
> 
> I _think_ we can move the bit into the unserialized section below.
> 
> It's a bit cheecky, but it should work I think because the only time we
> actually use this bit, we're guaranteed the task isn't actually running,
> so current doesn't exist.
> 

Putting the bit there has the added advantage that if the bit existed
on its own that it would be very special in terms of how it should be
treated. Adding a bit adjacent to it would be potentially hazardous.

> ---
> Subject: sched: Fix data-race in wakeup
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Tue Nov 17 09:08:41 CET 2020
>  
> <SNIP>
> 
> Fixes: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu")
> Reported-by: Mel Gorman <mgorman@techsingularity.net>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Thanks, testing completed successfully! With the suggested alternative
comment above sched_remote_wakeup;

Reviewed-by: Mel Gorman <mgorman@techsingularity.net>

-- 
Mel Gorman
SUSE Labs

  parent reply	other threads:[~2020-11-17 12:40 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-16  9:10 Loadavg accounting error on arm64 Mel Gorman
2020-11-16 11:49 ` Mel Gorman
2020-11-16 12:00   ` Mel Gorman
2020-11-16 12:53   ` Peter Zijlstra
2020-11-16 12:58     ` Peter Zijlstra
2020-11-16 15:29       ` Mel Gorman
2020-11-16 16:42         ` Mel Gorman
2020-11-16 16:49         ` Peter Zijlstra
2020-11-16 17:24           ` Mel Gorman
2020-11-16 17:41             ` Will Deacon
2020-11-16 12:46 ` Peter Zijlstra
2020-11-16 12:58   ` Mel Gorman
2020-11-16 13:11 ` Will Deacon
2020-11-16 13:37   ` Mel Gorman
2020-11-16 14:20     ` Peter Zijlstra
2020-11-16 15:52       ` Mel Gorman
2020-11-16 16:54         ` Peter Zijlstra
2020-11-16 17:16           ` Mel Gorman
2020-11-16 19:31       ` Mel Gorman
2020-11-17  8:30         ` [PATCH] sched: Fix data-race in wakeup Peter Zijlstra
2020-11-17  9:15           ` Will Deacon
2020-11-17  9:29             ` Peter Zijlstra
2020-11-17  9:46               ` Peter Zijlstra
2020-11-17 10:36                 ` Will Deacon
2020-11-17 12:52                 ` Valentin Schneider
2020-11-17 15:37                   ` Valentin Schneider
2020-11-17 16:13                     ` Peter Zijlstra
2020-11-17 19:32                       ` Valentin Schneider
2020-11-18  8:05                         ` Peter Zijlstra
2020-11-18  9:51                           ` Valentin Schneider
2020-11-18 13:33               ` Marco Elver
2020-11-17  9:38           ` [PATCH] sched: Fix rq->nr_iowait ordering Peter Zijlstra
2020-11-17 11:43             ` Mel Gorman
2020-11-19  9:55             ` [tip: sched/urgent] " tip-bot2 for Peter Zijlstra
2020-11-17 12:40           ` Mel Gorman [this message]
2020-11-19  9:55           ` [tip: sched/urgent] sched: Fix data-race in wakeup tip-bot2 for Peter Zijlstra

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