From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Venki Pallipadi <venki@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <andi@firstfloor.org>,
Tim Chen <tim.c.chen@linux.intel.com>,
Ingo Molnar <mingo@elte.hu>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [Patch] Idle balancer: cache align nohz structure to improve idle load balancing scalability
Date: Wed, 2 Nov 2011 19:24:14 +0530 [thread overview]
Message-ID: <20111102135414.GC6820@linux.vnet.ibm.com> (raw)
In-Reply-To: <1320191558.28097.44.camel@sbsiddha-desk.sc.intel.com>
* Suresh Siddha <suresh.b.siddha@intel.com> [2011-11-01 16:52:38]:
> + /*
> + * We were recently in tickless idle mode. We will do the delayed
> + * update of busy mode now (first busy tick after returning from idle).
> + */
> + if (unlikely(rq->tick_stopped)) {
> + cpumask_clear_cpu(cpu, nohz.idle_cpus_mask);
> +
> + if (cpumask_bits(nohz.idle_cpus_mask)[BIT_WORD(cpu)] == 0 &&
> + cpumask_empty(nohz.idle_cpus_mask))
> + clear_bit(NOHZ_NEED_BALANCING, &nohz.bits);
Can't this clear_bit race with set_bit() in select_nohz_load_balancer()?
CPU0 CPU1
cpumask_clear_cpu()
if ( ...)
cpumask_set_cpu();
set_bit();
clear_bit();
?
- vatsa
next prev parent reply other threads:[~2011-11-02 13:54 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-19 21:45 [Patch] Idle balancer: cache align nohz structure to improve idle load balancing scalability Tim Chen
2011-10-20 4:18 ` Eric Dumazet
2011-10-20 5:57 ` Suresh Siddha
2011-10-20 6:43 ` Eric Dumazet
2011-10-20 17:19 ` Tim Chen
2011-10-20 4:24 ` Andi Kleen
2011-10-20 12:26 ` Venki Pallipadi
2011-10-20 17:31 ` Suresh Siddha
2011-10-20 17:38 ` Peter Zijlstra
[not found] ` <4FF5AC937153B0459463C1A88EB478F20135D6ECB5@orsmsx505.amr.corp.intel.com>
2011-11-01 23:52 ` Suresh Siddha
2011-11-02 13:04 ` Srivatsa Vaddagiri
2011-11-02 13:54 ` Srivatsa Vaddagiri [this message]
2011-11-02 15:13 ` Suresh Siddha
2011-11-14 9:32 ` Peter Zijlstra
2011-11-14 19:37 ` Suresh Siddha
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