From: Peter Zijlstra <peterz@infradead.org>
To: Don Zickus <dzickus@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org
Subject: Re: fix BUG: using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog
Date: Mon, 16 Aug 2010 16:29:08 +0200 [thread overview]
Message-ID: <1281968948.1926.1467.camel@laptop> (raw)
In-Reply-To: <20100816141250.GU4879@redhat.com>
On Mon, 2010-08-16 at 10:12 -0400, Don Zickus wrote:
> On Mon, Aug 16, 2010 at 03:46:58PM +0200, Peter Zijlstra wrote:
> > > I don't see a problem with the patch, but my low level understanding of
> > > the __get_cpu_var vs. per_cpu isn't very strong.
> >
> > __get_cpu_var() gets you the value on the current cpu, per_cpu() takes a
> > cpu argument.
>
> Well I know that much. :-) It seems that __get_cpu_var depends on
> preemption being disabled whereas per_cpu does not? Though for some
> reason I thought __get_cpu_var would be more atomic when it grabbed the
> current cpu such that you wouldn't need to disable preemption. Guess not.
Indeed, it can't be implemented atomically on all smp systems, hence its
really nothing other than a 'convenient' short for per_cpu(foo,
smp_processor_id()).
next prev parent reply other threads:[~2010-08-16 14:29 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-13 10:21 fix BUG: using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog Sergey Senozhatsky
2010-08-16 8:22 ` Peter Zijlstra
2010-08-16 13:34 ` Don Zickus
2010-08-16 13:46 ` Peter Zijlstra
2010-08-16 14:08 ` [PATCH] fix BUG " Sergey Senozhatsky
2010-08-16 14:30 ` Don Zickus
2010-08-17 4:27 ` Yong Zhang
2010-08-17 2:59 ` Frederic Weisbecker
2010-08-17 3:16 ` Yong Zhang
2010-08-17 8:39 ` Sergey Senozhatsky
2010-08-17 9:05 ` Yong Zhang
2010-08-17 9:24 ` Sergey Senozhatsky
2010-08-17 9:37 ` Yong Zhang
2010-08-17 10:28 ` Sergey Senozhatsky
2010-08-17 12:48 ` Yong Zhang
2010-08-17 10:39 ` Sergey Senozhatsky
2010-08-17 12:56 ` Yong Zhang
2010-08-17 13:13 ` Don Zickus
2010-08-18 2:48 ` Frederic Weisbecker
2010-08-18 20:01 ` Andrew Morton
2010-08-19 2:27 ` Don Zickus
2010-08-20 2:57 ` Don Zickus
2010-08-20 3:42 ` Andrew Morton
2010-08-20 12:34 ` Don Zickus
2010-08-26 17:17 ` acpi_os_stall() and touch_nmi_watchdog() (was Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog) Len Brown
2010-08-20 15:02 ` [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog Yong Zhang
2010-08-26 10:14 ` Maxim Levitsky
2010-08-26 14:40 ` Don Zickus
2010-08-17 7:56 ` [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog (v2) Sergey Senozhatsky
2010-08-16 14:12 ` fix BUG: using smp_processor_id() in touch_nmi_watchdog and touch_softlockup_watchdog Don Zickus
2010-08-16 14:29 ` Peter Zijlstra [this message]
2010-08-16 14:06 ` Yong Zhang
2010-08-18 19:33 ` Andrew Morton
2010-08-18 21:44 ` Cyrill Gorcunov
2010-09-22 9:00 ` [PATCH] avoid second smp_processor_id() call in __touch_watchdog Sergey Senozhatsky
2010-09-22 14:41 ` Don Zickus
2010-09-22 16:27 ` Frederic Weisbecker
2010-09-22 16:39 ` Peter Zijlstra
2010-09-22 16:47 ` Frederic Weisbecker
2010-09-24 19:34 ` Don Zickus
2010-09-25 17:43 ` Sergey Senozhatsky
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