From: Oleg Nesterov <oleg@redhat.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Chris Mason <chris.mason@oracle.com>,
Frank Rowand <frank.rowand@am.sony.com>,
Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
Mike Galbraith <efault@gmx.de>, Paul Turner <pjt@google.com>,
Jens Axboe <axboe@kernel.dk>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 2/5] mutex: Use p->oncpu for the adaptive spin
Date: Fri, 17 Dec 2010 20:17:13 +0100 [thread overview]
Message-ID: <20101217191713.GA15381@redhat.com> (raw)
In-Reply-To: <1292527743.2708.75.camel@laptop>
On 12/16, Peter Zijlstra wrote:
>
> So yea, I think we can simplify all this even further, but we do need a
> smp_rmb() in between those two checks, hmm, and RCU.
I am not sure we need rmb() or even read_barrier_depends(), I think
the simple barrier() should be enough. Although rcu_dereference()
may be more clean.
We don't really care about the "correct" result of *owner. All we need,
we should ensure it is safe to dereference this address. If CPU itself
does something like "readahead" before we verified "lock->owner == owner"
under RCU lock, this shouldn't lead to the fault.
Oleg.
next prev parent reply other threads:[~2010-12-17 19:24 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-16 14:56 [RFC][PATCH 0/5] Reduce runqueue lock contention -v2 Peter Zijlstra
2010-12-16 14:56 ` [RFC][PATCH 1/5] sched: Always provide p->oncpu Peter Zijlstra
2010-12-18 1:03 ` Frank Rowand
2010-12-16 14:56 ` [RFC][PATCH 2/5] mutex: Use p->oncpu for the adaptive spin Peter Zijlstra
2010-12-16 17:34 ` Oleg Nesterov
2010-12-16 19:29 ` Peter Zijlstra
2010-12-17 19:17 ` Oleg Nesterov [this message]
2010-12-16 14:56 ` [RFC][PATCH 3/5] sched: Change the ttwu success details Peter Zijlstra
2010-12-16 15:23 ` Frederic Weisbecker
2010-12-16 15:27 ` Peter Zijlstra
2010-12-16 15:30 ` Peter Zijlstra
2010-12-16 15:45 ` Frederic Weisbecker
2010-12-16 15:35 ` Frederic Weisbecker
2010-12-18 1:05 ` Frank Rowand
2010-12-16 14:56 ` [RFC][PATCH 4/5] sched: Clean up ttwu stats Peter Zijlstra
2010-12-18 1:09 ` Frank Rowand
2010-12-16 14:56 ` [RFC][PATCH 5/5] sched: Reduce ttwu rq->lock contention Peter Zijlstra
2010-12-16 15:31 ` Frederic Weisbecker
2010-12-16 17:58 ` Oleg Nesterov
2010-12-16 18:42 ` Oleg Nesterov
2010-12-16 18:58 ` Peter Zijlstra
2010-12-16 19:03 ` Peter Zijlstra
2010-12-16 19:47 ` Peter Zijlstra
2010-12-16 20:32 ` Peter Zijlstra
2010-12-17 3:06 ` Yan, Zheng
2010-12-17 13:23 ` Peter Zijlstra
2010-12-17 16:54 ` Oleg Nesterov
2010-12-17 17:43 ` Peter Zijlstra
2010-12-17 18:15 ` Peter Zijlstra
2010-12-17 19:28 ` Oleg Nesterov
2010-12-17 21:02 ` Peter Zijlstra
2010-12-18 14:49 ` Yong Zhang
2010-12-18 20:08 ` Oleg Nesterov
2010-12-19 11:20 ` Yong Zhang
2010-12-17 18:21 ` Oleg Nesterov
2010-12-17 17:50 ` Oleg Nesterov
2010-12-17 18:24 ` Peter Zijlstra
2010-12-17 18:41 ` Peter Zijlstra
2010-12-16 19:12 ` [RFC][PATCH 0/5] Reduce runqueue lock contention -v2 Frank Rowand
2010-12-16 19:36 ` Frank Rowand
2010-12-16 19:39 ` Frank Rowand
2010-12-16 19:42 ` Peter Zijlstra
2010-12-16 20:45 ` Frank Rowand
2010-12-16 19:36 ` Frank Rowand
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