From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca,
josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de,
rostedt@goodmis.org, Valdis.Kletnieks@vt.edu,
dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com,
fweisbec@gmail.com, patches@linaro.org,
"Paul E. McKenney" <paul.mckenney@linaro.org>
Subject: Re: [PATCH RFC tip/core/rcu 4/4] rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU
Date: Thu, 26 Apr 2012 08:54:50 -0700 [thread overview]
Message-ID: <20120426155450.GD2407@linux.vnet.ibm.com> (raw)
In-Reply-To: <1335445496.13683.21.camel@twins>
On Thu, Apr 26, 2012 at 03:04:56PM +0200, Peter Zijlstra wrote:
> On Mon, 2012-04-23 at 09:16 -0700, Paul E. McKenney wrote:
> > - mod_timer(&per_cpu(rcu_idle_gp_timer, cpu),
> > - per_cpu(rcu_idle_gp_timer_expires, cpu));
> > + tp = &per_cpu(rcu_idle_gp_timer, cpu);
> > + tp->expires = per_cpu(rcu_idle_gp_timer_expires, cpu);
> > + add_timer_on(tp, cpu);
>
> The simpler change looks to use mod_timer_pinned()
Good point!
Except... Now that you mention it, I don't see how mod_timer_pinned()
actually helps. It looks to me like a CPU-hotplug operation will
migrate the timers anyway.
This is actually (in theory) harmless in the RCU_FAST_NO_HZ case, because
the CPU_DYING stuff will force a wakeup of the CPU in question, which
will cancel the timer. But still, mod_timer_pinned() has a rather
misleading name. ;-)
But a line is a line, so I made this change.
Thanx, Paul
next prev parent reply other threads:[~2012-04-26 15:55 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 16:15 [PATCH RFC tip/core/rcu 0/4] Updates to RCU_FAST_NO_HZ Paul E. McKenney
2012-04-23 16:15 ` [PATCH RFC tip/core/rcu 1/4] rcu: Add RCU_FAST_NO_HZ tracing for idle exit Paul E. McKenney
2012-04-23 16:15 ` [PATCH RFC tip/core/rcu 2/4] rcu: Make RCU_FAST_NO_HZ use timer rather than hrtimer Paul E. McKenney
2012-04-23 16:16 ` [PATCH RFC tip/core/rcu 3/4] rcu: Make RCU_FAST_NO_HZ account for pauses out of idle Paul E. McKenney
2012-04-26 13:00 ` Peter Zijlstra
2012-04-26 14:49 ` Paul E. McKenney
2012-04-26 15:09 ` Peter Zijlstra
2012-04-23 16:16 ` [PATCH RFC tip/core/rcu 4/4] rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU Paul E. McKenney
2012-04-26 13:04 ` Peter Zijlstra
2012-04-26 15:54 ` Paul E. McKenney [this message]
2012-04-26 16:08 ` Steven Rostedt
2012-04-26 17:56 ` Paul E. McKenney
2012-04-26 18:10 ` [PATCH] timer: Fix mod_timer_pinned() header commen (was: [PATCH RFC tip/core/rcu 4/4] rcu: Ensure that RCU_FAST_NO_HZ timers expire on correct CPU) Steven Rostedt
2012-04-26 18:36 ` Paul E. McKenney
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