From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: tglx@linutronix.de, peterz@infradead.org,
paulmck@linux.vnet.ibm.com, rusty@rustcorp.com.au,
mingo@kernel.org, akpm@linux-foundation.org, namhyung@kernel.org,
vincent.guittot@linaro.org, tj@kernel.org, sbw@mit.edu,
amit.kucheria@linaro.org, rostedt@goodmis.org, rjw@sisk.pl,
wangyun@linux.vnet.ibm.com, xiaoguangrong@linux.vnet.ibm.com,
nikunj@linux.vnet.ibm.com, linux-pm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v3 7/9] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly
Date: Mon, 10 Dec 2012 01:27:58 +0530 [thread overview]
Message-ID: <50C4ED46.3070100@linux.vnet.ibm.com> (raw)
In-Reply-To: <20121209194826.GB2816@redhat.com>
On 12/10/2012 01:18 AM, Oleg Nesterov wrote:
> On 12/07, Srivatsa S. Bhat wrote:
>>
>> Once stop_machine() is gone from the CPU offline path, we won't be able to
>> depend on local_irq_save() to prevent CPUs from going offline from under us.
>
> OK, I guess we need to avoid resched_task()->smp_send_reschedule()
> after __cpu_disable() and before migrate_tasks().
>
Yes.
> But, whatever problem we have,
>
>> Use the get/put_online_cpus_atomic() APIs to prevent CPUs from going offline,
>> while invoking from atomic context.
>
> it should be solved, so...
>
>> - if (preempt && rq != p_rq)
>> + if (preempt && rq != p_rq && cpu_online(task_cpu(p)))
>
> Why do we need this change?
>
> Afaics, you could add BUG_ON(!cpu_online(...)) instead?
>
> I am just curious.
>
Oh, I think that's a remnant of v1 (which needed readers to use
cpu_online_stable()). You're right, we don't need it. Or we could put a
BUG_ON instead, like you suggested.
Regards,
Srivatsa S. Bhat
next prev parent reply other threads:[~2012-12-09 19:59 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-07 17:37 [RFC PATCH v3 0/9] CPU hotplug: stop_machine()-free CPU hotplug Srivatsa S. Bhat
2012-12-07 17:38 ` [RFC PATCH v3 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context Srivatsa S. Bhat
2012-12-07 17:57 ` Tejun Heo
2012-12-07 18:16 ` Tejun Heo
2012-12-07 18:33 ` Srivatsa S. Bhat
2012-12-07 18:24 ` Srivatsa S. Bhat
2012-12-07 18:31 ` Tejun Heo
2012-12-07 18:38 ` Srivatsa S. Bhat
2012-12-09 19:14 ` Oleg Nesterov
2012-12-09 19:50 ` Srivatsa S. Bhat
2012-12-09 20:22 ` Oleg Nesterov
2012-12-10 4:28 ` Srivatsa S. Bhat
2012-12-10 17:24 ` Oleg Nesterov
2012-12-11 13:13 ` Srivatsa S. Bhat
2012-12-11 13:47 ` Tejun Heo
2012-12-11 14:02 ` Srivatsa S. Bhat
2012-12-11 14:07 ` Tejun Heo
2012-12-11 16:28 ` Srivatsa S. Bhat
2012-12-09 21:13 ` Oleg Nesterov
2012-12-10 5:01 ` Srivatsa S. Bhat
2012-12-10 17:28 ` Oleg Nesterov
2012-12-11 13:05 ` Srivatsa S. Bhat
2012-12-09 20:57 ` Oleg Nesterov
2012-12-10 5:19 ` Srivatsa S. Bhat
2012-12-10 18:15 ` Oleg Nesterov
2012-12-11 13:04 ` Srivatsa S. Bhat
2012-12-07 17:38 ` [RFC PATCH v3 2/9] CPU hotplug: Convert preprocessor macros to static inline functions Srivatsa S. Bhat
2012-12-07 17:38 ` [RFC PATCH v3 3/9] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Srivatsa S. Bhat
2012-12-07 17:39 ` [RFC PATCH v3 4/9] smp, cpu hotplug: Fix on_each_cpu_*() " Srivatsa S. Bhat
2012-12-07 17:39 ` [RFC PATCH v3 5/9] sched, cpu hotplug: Use stable online cpus in try_to_wake_up() & select_task_rq() Srivatsa S. Bhat
2012-12-07 17:39 ` [RFC PATCH v3 6/9] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Srivatsa S. Bhat
2012-12-07 17:39 ` [RFC PATCH v3 7/9] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly Srivatsa S. Bhat
2012-12-09 19:48 ` Oleg Nesterov
2012-12-09 19:57 ` Srivatsa S. Bhat [this message]
2012-12-09 20:40 ` Oleg Nesterov
2012-12-10 4:04 ` Srivatsa S. Bhat
2012-12-07 17:40 ` [RFC PATCH v3 8/9] kvm, vmx: Add atomic synchronization with CPU Hotplug Srivatsa S. Bhat
2012-12-07 17:40 ` [RFC PATCH v3 9/9] cpu: No more __stop_machine() in _cpu_down() Srivatsa S. Bhat
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