From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Oleg Nesterov <oleg@redhat.com>,
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: Thu, 1 Sep 2016 17:33:10 +0200 [thread overview]
Message-ID: <20160901153310.GW10153@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20160901141757.GA24098@tardis.cn.ibm.com>
On Thu, Sep 01, 2016 at 10:17:57PM +0800, Boqun Feng wrote:
> On Thu, Sep 01, 2016 at 08:57:38AM +0200, Peter Zijlstra wrote:
> Could there be some code that relies on the full barrier semantics of
> schedule() to provide transitivity?
Could, sure, who knows. RCU might, although Paul typically sticks in
smp_mb just to be safe.
The kernel coming apart when you remove that sync would prove this
fairly quick though.
Like Ben said, it not coming apart doesn't prove anything. It coming
apart does however prove something, namely that it is required :-)
> IIUC, the Program Order Guarantee you stated before try_to_wake_up()
> only has ordering effect on wakers and wakees.
Right, the scheduler only does RCpc guarantees.
next prev parent reply other threads:[~2016-09-01 15:33 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-30 8:49 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 [this message]
2016-08-30 21:25 ` Benjamin Herrenschmidt
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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