From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>,
linux-kernel@vger.kernel.org, Don Zickus <dzickus@redhat.com>,
Cyrill Gorcunov <gorcunov@gmail.com>
Subject: Re: [PATCH] avoid second smp_processor_id() call in __touch_watchdog
Date: Wed, 22 Sep 2010 18:47:05 +0200 [thread overview]
Message-ID: <20100922164703.GD5302@nowhere> (raw)
In-Reply-To: <1285173559.2275.1024.camel@laptop>
On Wed, Sep 22, 2010 at 06:39:19PM +0200, Peter Zijlstra wrote:
> On Wed, 2010-09-22 at 18:27 +0200, Frederic Weisbecker wrote:
> >
> > I'm not sure we want this. This is called by the watchdog internally,
> > from the timer or the cpu bound thread, so we probably should better
> > keep __get_cpu_var() because it checks that we are not in a preemptable
> > section.
>
> The smp_processor_id() right at the start already does that.
>
> That said, I doubt it really matter one way or the other, compilers have
> been known to do CSE for quite a while.
I don't mind personally. We indeed have this smp_processor_id() that
does the check already. But that's also for readability: reviewers
that are used to deal with per cpu datas are also used to see
per_cpu() for remote percpu data access and get_cpu_var() for local
percpu.
Plus some archs may override their __my_cpu_offset implementation
to provide a faster access.
next prev parent reply other threads:[~2010-09-22 16:47 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
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 [this message]
2010-09-24 19:34 ` Don Zickus
2010-09-25 17:43 ` Sergey Senozhatsky
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