From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Prarit Bhargava <prarit@redhat.com>,
Rick Lindsley <ricklind@us.ibm.com>,
john stultz <johnstul@us.ibm.com>, Ingo Molnar <mingo@elte.hu>,
Linux Kernel <linux-kernel@vger.kernel.org>,
virtualization@lists.osdl.org, Paul Mackerras <paulus@samba.org>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [patch 1/2] Ignore stolen time in the softlockup watchdog
Date: Tue, 27 Mar 2007 00:12:53 -0700 [thread overview]
Message-ID: <4608C3F5.1030106@goop.org> (raw)
In-Reply-To: <4608C121.4050309@cosmosbay.com>
Eric Dumazet wrote:
> Jeremy Fitzhardinge a écrit :
>
>> +static DEFINE_PER_CPU(unsigned long long, touch_timestamp);
>
> ...
>
>> void touch_softlockup_watchdog(void)
>> {
>> - __raw_get_cpu_var(touch_timestamp) = jiffies;
>> + __raw_get_cpu_var(touch_timestamp) = sched_clock();
>> }
>
> Not very clear if this is safe on 32bit, since this is not anymore
> atomic.
Hm, good point. Don't think it matters very much. These values are
per-cpu, and if an interrupt happens between the word updates and the
intermediate values causes a timeout, then it was pretty marginal
anyway. I guess the worst case is if the low-word gets written first,
and it goes from a high value to low, then it could be sampled as if
time had gone back by up to ~4 seconds.
I'll give it another look.
J
next prev parent reply other threads:[~2007-03-27 7:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-03-27 5:38 [patch 0/2] softlockup watchdog improvements Jeremy Fitzhardinge
2007-03-27 5:38 ` [patch 1/2] Ignore stolen time in the softlockup watchdog Jeremy Fitzhardinge
2007-03-27 7:00 ` Eric Dumazet
2007-03-27 7:12 ` Jeremy Fitzhardinge [this message]
2007-03-27 7:50 ` Eric Dumazet
2007-03-27 14:39 ` Prarit Bhargava
2007-03-27 16:37 ` Jeremy Fitzhardinge
2007-03-27 16:53 ` Prarit Bhargava
2007-03-27 17:10 ` Jeremy Fitzhardinge
2007-03-27 17:20 ` Prarit Bhargava
2007-03-27 5:38 ` [patch 2/2] percpu enable flag for " Jeremy Fitzhardinge
2007-03-27 14:42 ` Prarit Bhargava
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