From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Oleg Nesterov <oleg@redhat.com>, Peter Zijlstra <peterz@infradead.org>
Cc: Balbir Singh <bsingharora@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Nicholas Piggin <nicholas.piggin@gmail.com>
Subject: Re: [RFC][PATCH] Fix a race between rwsem and the scheduler
Date: Wed, 31 Aug 2016 07:25:01 +1000 [thread overview]
Message-ID: <1472592301.2388.37.camel@kernel.crashing.org> (raw)
In-Reply-To: <20160830130426.GA17795@redhat.com>
On Tue, 2016-08-30 at 15:04 +0200, Oleg Nesterov wrote:
>
> Confused... how this connects to UNLOCK+LOCK on rq->lock? A LOAD can
> leak into the critical section.
>
> But context switch should imply mb() we can rely on?
Between setting of ->on_rq and returning to the task so it can
change its state back to [UN]INTERRUPTIBLE, there will be at least one
write barrier (spin unlock of the rq), possibly even a full barrier
(context switch). The write barrier is enough so I didn't dig to make
sure we always context switch in the scenario we're looking at but I
think we do.
Cheers,
Ben.
next prev parent reply other threads:[~2016-08-30 21:25 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 8:49 [RFC][PATCH] Fix a race between rwsem and the scheduler Balbir Singh
2016-08-30 9:13 ` Nicholas Piggin
2016-08-30 12:19 ` Peter Zijlstra
2016-08-30 13:04 ` Oleg Nesterov
2016-08-30 14:13 ` Peter Zijlstra
2016-08-30 16:57 ` Oleg Nesterov
2016-08-30 18:34 ` Peter Zijlstra
2016-08-30 21:28 ` Benjamin Herrenschmidt
2016-08-31 7:18 ` Peter Zijlstra
2016-08-31 10:56 ` Benjamin Herrenschmidt
2016-08-31 13:31 ` Peter Zijlstra
2016-08-31 21:47 ` Benjamin Herrenschmidt
2016-09-01 6:49 ` Balbir Singh
2016-09-01 6:57 ` Peter Zijlstra
2016-09-01 14:17 ` Boqun Feng
2016-09-01 15:33 ` Peter Zijlstra
2016-08-30 21:25 ` Benjamin Herrenschmidt [this message]
2016-08-31 7:20 ` Peter Zijlstra
2016-08-31 10:55 ` Benjamin Herrenschmidt
2016-08-31 3:41 ` Balbir Singh
2016-08-31 7:28 ` Peter Zijlstra
2016-08-31 10:17 ` Balbir Singh
2016-08-31 10:57 ` Benjamin Herrenschmidt
2016-09-01 1:48 ` Alexey Kardashevskiy
2016-09-01 12:16 ` Alexey Kardashevskiy
2016-08-30 12:58 ` Oleg Nesterov
2016-08-31 3:25 ` Balbir Singh
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