From: Joel Becker <Joel.Becker@oracle.com>
To: Yury Polyanskiy <ypolyans@princeton.edu>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
john stultz <johnstul@us.ibm.com>,
Jan Glauber <jan.glauber@de.ibm.com>
Subject: Re: [PATCH] hangcheck-timer is broken on x86
Date: Sat, 27 Mar 2010 16:36:30 -0700 [thread overview]
Message-ID: <20100327233630.GB1810@mail.oracle.com> (raw)
In-Reply-To: <ea182b21003271551k10d0ef1oa0757ba921f1870f@mail.gmail.com>
On Sat, Mar 27, 2010 at 06:51:01PM -0400, Yury Polyanskiy wrote:
> > It's OK to tell hangcheck-timer users that suspend is not
> > allowed. After all, you're running something that you don't want to see
> > hang.
>
> Joel, what I am saying is exactly the opposite: it is totally ok to
> suspend-resume with hangcheck-timer (jiffies are stopped and so is
> getrawmonotonic() when system suspended).
Nope. The point of hangcheck-timer is that it reboots should
the system not be running for a certain amountof time. If
suspend-resume is allowed, a system can resume after days and think it
wasn't more than a second. hangcheck-timer will not know to reboot.
> > Is there a clock in the system that is a true wallclock? I'm
> > guessing, since getrawmonotonic() is get_cycles() based, that it doesn't
> > provide accurate time in the face of cpufreq changes. Is that true?
>
> Of course, getrawmonotonic accounts for cpufreq changes (see
> arch/x86/kernel/tsc.c:time_cpufreq_notifier()).
Excellent! That's a definite improvement over raw get_cycles().
Joel
--
Life's Little Instruction Book #182
"Be romantic."
Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@oracle.com
Phone: (650) 506-8127
next prev parent reply other threads:[~2010-03-27 23:37 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-24 3:36 [PATCH] hangcheck-timer is broken on x86 Yury Polyanskiy
2010-03-26 21:24 ` Andrew Morton
2010-03-26 21:52 ` Yury Polyanskiy
2010-03-26 21:46 ` Joel Becker
2010-03-26 22:00 ` Yury Polyanskiy
2010-03-27 0:57 ` Joel Becker
2010-03-27 2:02 ` Yury Polyanskiy
2010-03-27 22:03 ` Joel Becker
2010-03-27 22:51 ` Yury Polyanskiy
2010-03-27 23:36 ` Joel Becker [this message]
2010-03-28 2:08 ` Yury Polyanskiy
2010-03-29 1:00 ` john stultz
2010-03-29 14:11 ` Yury Polyanskiy
2010-03-29 16:43 ` john stultz
2010-03-29 17:04 ` Yury Polyanskiy
2010-03-29 18:44 ` john stultz
2010-03-29 19:53 ` Joel Becker
2010-03-29 21:08 ` Yury Polyanskiy
2010-03-29 21:43 ` john stultz
2010-03-29 22:34 ` Yury Polyanskiy
2010-04-08 0:52 ` Joel Becker
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