From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: linux-kernel@vger.kernel.org,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>,
akpm@linux-foundation.org, josh@joshtriplett.org,
tglx@linutronix.de, Valdis.Kletnieks@vt.edu, dhowells@redhat.com,
laijs@cn.fujitsu.com, dipankar@in.ibm.com
Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier (v5)
Date: Wed, 13 Jan 2010 17:38:58 +0100 [thread overview]
Message-ID: <1263400738.4244.242.camel@laptop> (raw)
In-Reply-To: <20100113013757.GA29314@Krystal>
On Tue, 2010-01-12 at 20:37 -0500, Mathieu Desnoyers wrote:
> + for_each_cpu(cpu, tmpmask) {
> + spin_lock_irq(&cpu_rq(cpu)->lock);
> + mm = cpu_curr(cpu)->mm;
> + spin_unlock_irq(&cpu_rq(cpu)->lock);
> + if (current->mm != mm)
> + cpumask_clear_cpu(cpu, tmpmask);
> + }
Why not:
rcu_read_lock();
if (current->mm != cpu_curr(cpu)->mm)
cpumask_clear_cpu(cpu, tmpmask);
rcu_read_unlock();
the RCU read lock ensures the task_struct obtained remains valid, and it
avoids taking the rq->lock.
next prev parent reply other threads:[~2010-01-13 16:40 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-13 1:37 [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier (v5) Mathieu Desnoyers
2010-01-13 3:23 ` KOSAKI Motohiro
2010-01-13 3:58 ` Mathieu Desnoyers
2010-01-13 4:47 ` KOSAKI Motohiro
2010-01-13 5:33 ` Paul E. McKenney
2010-01-13 15:03 ` Mathieu Desnoyers
2010-01-14 0:15 ` KOSAKI Motohiro
2010-01-14 2:16 ` Mathieu Desnoyers
2010-01-14 2:25 ` KOSAKI Motohiro
2010-01-13 5:00 ` Nicholas Miell
2010-01-13 5:31 ` Paul E. McKenney
2010-01-13 5:39 ` Nicholas Miell
2010-01-13 14:38 ` Mathieu Desnoyers
2010-01-13 18:07 ` Nicholas Miell
2010-01-13 18:24 ` Mathieu Desnoyers
2010-01-13 18:41 ` Nicholas Miell
2010-01-13 19:17 ` Mathieu Desnoyers
2010-01-13 19:42 ` David Daney
2010-01-13 19:53 ` Nicholas Miell
2010-01-13 23:42 ` Mathieu Desnoyers
2010-01-13 15:58 ` Paul E. McKenney
2010-01-13 11:07 ` Heiko Carstens
2010-01-13 14:46 ` Mathieu Desnoyers
2010-01-13 16:38 ` Peter Zijlstra [this message]
2010-01-13 19:36 ` Mathieu Desnoyers
2010-01-14 9:08 ` Peter Zijlstra
2010-01-14 16:26 ` Mathieu Desnoyers
2010-01-14 17:03 ` Peter Zijlstra
2010-01-14 17:54 ` Mathieu Desnoyers
2010-01-14 18:37 ` Mathieu Desnoyers
2010-01-14 18:52 ` Steven Rostedt
2010-01-14 19:33 ` Mathieu Desnoyers
2010-01-14 21:26 ` Steven Rostedt
2010-01-19 18:37 ` Peter Zijlstra
2010-01-19 19:06 ` Peter Zijlstra
2010-01-20 3:13 ` Mathieu Desnoyers
2010-01-20 8:45 ` Peter Zijlstra
2010-01-21 11:26 ` Peter Zijlstra
2010-01-21 16:07 ` Mathieu Desnoyers
2010-01-21 16:12 ` Steven Rostedt
2010-01-21 16:22 ` Mathieu Desnoyers
2010-01-21 16:32 ` Steven Rostedt
2010-01-21 17:02 ` Mathieu Desnoyers
2010-01-21 16:17 ` Peter Zijlstra
2010-01-21 17:01 ` Mathieu Desnoyers
2010-01-19 19:43 ` Steven Rostedt
2010-01-14 18:50 ` Steven Rostedt
2010-01-19 16:47 ` Peter Zijlstra
2010-01-19 17:11 ` Mathieu Desnoyers
2010-01-19 17:30 ` Steven Rostedt
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