From: Tejun Heo <tj@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
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, 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 v4 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context
Date: Thu, 13 Dec 2012 08:32:33 -0800 [thread overview]
Message-ID: <20121213163233.GA2728@htj.dyndns.org> (raw)
In-Reply-To: <20121213161709.GA19125@redhat.com>
Hello, Oleg.
On Thu, Dec 13, 2012 at 05:17:09PM +0100, Oleg Nesterov wrote:
> Hmm. I thought that __this_cpu_* must be safe under preempt_disable().
> IOW, I thought that, say, this_cpu_inc() is "equal" to preempt_disable +
> __this_cpu_inc() correctness-wise.
this_cpu_inc() equals local_irq_save() + __this_cpu_inc().
> And. I thought that this_cpu_inc() is safe wrt interrupt, like local_t.
Yes, it is safe.
> But when I try to read the comments percpu.h, I am starting to think that
> even this_cpu_inc() is not safe if irq handler can do the same?
>
> Confused...
Yeah, the comment is confusing and the way these macros are defined
doesn't help. There used to be three variants and it looks like we
didn't update the comment while removing the preempt safe ones. Gotta
clean those up. Anyways, yes, this_cpu_*() are safe against irqs.
Thanks.
--
tejun
next prev parent reply other threads:[~2012-12-13 16:32 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-11 14:03 [RFC PATCH v4 0/9] CPU hotplug: stop_machine()-free CPU hotplug Srivatsa S. Bhat
2012-12-11 14:04 ` [RFC PATCH v4 1/9] CPU hotplug: Provide APIs to prevent CPU offline from atomic context Srivatsa S. Bhat
2012-12-12 17:17 ` Oleg Nesterov
2012-12-12 17:24 ` Oleg Nesterov
2012-12-12 18:11 ` Srivatsa S. Bhat
2012-12-12 18:23 ` Oleg Nesterov
2012-12-12 18:42 ` Srivatsa S. Bhat
2012-12-12 17:53 ` Srivatsa S. Bhat
2012-12-12 18:02 ` Oleg Nesterov
2012-12-12 18:30 ` Srivatsa S. Bhat
2012-12-12 18:48 ` Oleg Nesterov
2012-12-12 19:12 ` Srivatsa S. Bhat
2012-12-13 15:26 ` Srivatsa S. Bhat
2012-12-13 16:17 ` Oleg Nesterov
2012-12-13 16:32 ` Srivatsa S. Bhat
2012-12-14 18:03 ` Oleg Nesterov
2012-12-18 15:53 ` Srivatsa S. Bhat
2012-12-18 19:43 ` Oleg Nesterov
2012-12-18 20:06 ` Srivatsa S. Bhat
2012-12-19 16:39 ` Oleg Nesterov
2012-12-19 18:16 ` Srivatsa S. Bhat
2012-12-19 19:14 ` Oleg Nesterov
2012-12-19 19:49 ` Srivatsa S. Bhat
2012-12-20 13:42 ` Oleg Nesterov
2012-12-20 14:06 ` Srivatsa S. Bhat
2012-12-22 20:17 ` Srivatsa S. Bhat
2012-12-23 16:42 ` Oleg Nesterov
2012-12-24 15:50 ` Srivatsa S. Bhat
2012-12-13 16:32 ` Tejun Heo [this message]
2012-12-12 19:36 ` Oleg Nesterov
2012-12-12 19:43 ` Srivatsa S. Bhat
2012-12-12 21:10 ` Oleg Nesterov
2012-12-11 14:04 ` [RFC PATCH v4 2/9] CPU hotplug: Convert preprocessor macros to static inline functions Srivatsa S. Bhat
2012-12-11 14:04 ` [RFC PATCH v4 3/9] smp, cpu hotplug: Fix smp_call_function_*() to prevent CPU offline properly Srivatsa S. Bhat
2012-12-11 14:04 ` [RFC PATCH v4 4/9] smp, cpu hotplug: Fix on_each_cpu_*() " Srivatsa S. Bhat
2012-12-11 14:05 ` [RFC PATCH v4 5/9] sched, cpu hotplug: Use stable online cpus in try_to_wake_up() & select_task_rq() Srivatsa S. Bhat
2012-12-11 14:05 ` [RFC PATCH v4 6/9] kick_process(), cpu-hotplug: Prevent offlining of target CPU properly Srivatsa S. Bhat
2012-12-11 14:05 ` [RFC PATCH v4 7/9] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly Srivatsa S. Bhat
2012-12-11 14:05 ` [RFC PATCH v4 8/9] kvm, vmx: Add atomic synchronization with CPU Hotplug Srivatsa S. Bhat
2012-12-11 14:05 ` [RFC PATCH v4 9/9] cpu: No more __stop_machine() in _cpu_down() Srivatsa S. Bhat
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