From: Tejun Heo <tj@kernel.org>
To: paulmck@linux.vnet.ibm.com
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>,
linux-kernel@vger.kernel.org, mingo@elte.hu, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
peterz@infradead.org, rostedt@goodmis.org,
Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
eric.dumazet@gmail.com, darren@dvhart.com
Subject: Re: [PATCH RFC tip/core/rcu 11/12] rcu: fix race condition in synchronize_sched_expedited()
Date: Thu, 11 Nov 2010 13:52:12 +0100 [thread overview]
Message-ID: <4CDBE6FC.1010106@kernel.org> (raw)
In-Reply-To: <20101111123146.GF3134@linux.vnet.ibm.com>
Hello,
On 11/11/2010 01:31 PM, Paul E. McKenney wrote:
> Actually, the memory barriers are still one source of discomfort to me.
> I am concerned about the path out of the function that skips the
> atomic_cmpxchg(), which seem to happen if some concurrent invocation
> advances the "done" counter past us before we get around to checking it.
> I agree on the atomic_inc_return() upon entry to the function, though.
Oooh, you're right. It needs to be smp_mb(). We can put it right
before break but I don't think it would worth the ugliness.
> And this is going to need some serious testing either way. ;-)
Definitely. This is a scary piece of code. :-)
--
tejun
next prev parent reply other threads:[~2010-11-11 12:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-07 2:05 [PATCH RFC tip/core/rcu 0/12] preview of RCU patches for 2.6.38 Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 01/12] rcu: add priority-inversion testing to rcutorture Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 02/12] rcu: move TINY_RCU from softirq to kthread Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 03/12] rcu: priority boosting for TINY_PREEMPT_RCU Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 04/12] rcu: add tracing for TINY_RCU and TINY_PREEMPT_RCU Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 05/12] rcu: document TINY_RCU and TINY_PREEMPT_RCU tracing Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 06/12] rcu: Distinguish between boosting and boosted Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 07/12] rcu: get rid of obsolete "classic" names in TREE_RCU tracing Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 08/12] rcu,cleanup: move synchronize_sched_expedited() out of sched.c Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 09/12] rcu,cleanup: simplify the code when cpu is dying Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 10/12] rcu: update documentation/comments for Lai's adoption patch Paul E. McKenney
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 11/12] rcu: fix race condition in synchronize_sched_expedited() Paul E. McKenney
2010-11-09 13:26 ` Tejun Heo
2010-11-10 8:56 ` Lai Jiangshan
2010-11-11 4:20 ` Paul E. McKenney
2010-11-11 9:10 ` Tejun Heo
2010-11-11 12:31 ` Paul E. McKenney
2010-11-11 12:52 ` Tejun Heo [this message]
2010-11-07 2:05 ` [PATCH RFC tip/core/rcu 12/12] rcu: Make synchronize_srcu_expedited() fast if running readers Paul E. McKenney
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