From: Oleg Nesterov <oleg@redhat.com>
To: Nicholas Mc Guire <der.herr@hofr.at>
Cc: Davidlohr Bueso <dave@stgolabs.net>,
paulmck@linux.vnet.ibm.com, linux-kernel@vger.kernel.org,
waiman.long@hp.com, peterz@infradead.org,
raghavendra.kt@linux.vnet.ibm.com
Subject: Re: BUG: spinlock bad magic on CPU#0, migration/0/9
Date: Sat, 14 Feb 2015 15:00:48 +0100 [thread overview]
Message-ID: <20150214140048.GA28535@redhat.com> (raw)
In-Reply-To: <20150214083555.GA30176@opentech.at>
On 02/14, Nicholas Mc Guire wrote:
>
> Basically if you call wait_for_completion_timeout and the timeout condition
> occures you always need some way of notifying the completing end that it
> should no longer call complete()/complete_all().
Sure. "struct completion" doesn't differ from any other object when it comes
to use-after-free.
> > OK, perhaps you can ack the fix I sent?
>
> the only question I still have is that there would be no matching
> smp_wmb() to the smp_rmb() you are using (atleast I did not figure out where).
You seem to assume that every rmb() must be paired with wmb(). This is not
always true.
But as for completion_done(), its rmb() pairs with "release" semantics of
complete()->spin_unlock(), which is a "one way" barrier.
Oleg.
next prev parent reply other threads:[~2015-02-14 14:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-12 0:34 BUG: spinlock bad magic on CPU#0, migration/0/9 Paul E. McKenney
2015-02-12 3:15 ` Davidlohr Bueso
2015-02-12 3:43 ` Paul E. McKenney
2015-02-12 17:28 ` Oleg Nesterov
2015-02-12 17:41 ` Oleg Nesterov
2015-02-12 17:58 ` Davidlohr Bueso
2015-02-12 19:10 ` Nicholas Mc Guire
2015-02-12 19:37 ` Oleg Nesterov
2015-02-12 21:27 ` Oleg Nesterov
2015-02-13 18:17 ` Nicholas Mc Guire
2015-02-13 18:53 ` Oleg Nesterov
2015-02-14 8:35 ` Nicholas Mc Guire
2015-02-14 14:00 ` Oleg Nesterov [this message]
2015-02-12 19:59 ` Davidlohr Bueso
2015-02-12 19:32 ` Nicholas Mc Guire
2015-02-12 19:39 ` Oleg Nesterov
2015-02-12 19:59 ` [PATCH] sched/completion: completion_done() should serialize with complete() Oleg Nesterov
2015-02-13 21:09 ` Paul E. McKenney
2015-02-13 21:56 ` Davidlohr Bueso
2015-02-13 22:02 ` Davidlohr Bueso
2015-02-16 8:21 ` Peter Zijlstra
2015-02-16 16:51 ` Oleg Nesterov
2015-02-18 17:06 ` [tip:sched/core] sched/completion: Serialize completion_done() " tip-bot for Oleg Nesterov
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