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From: Yury Polyanskiy <ypolyans@princeton.edu>
To: john stultz <johnstul@us.ibm.com>
Cc: Joel Becker <Joel.Becker@oracle.com>,
	linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
	Jan Glauber <jan.glauber@de.ibm.com>
Subject: Re: [PATCH] hangcheck-timer is broken on x86
Date: Mon, 29 Mar 2010 10:11:06 -0400	[thread overview]
Message-ID: <20100329101106.3678a312@penta.localdomain> (raw)
In-Reply-To: <1269824436.1880.2.camel@work-vm>

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On Sun, 28 Mar 2010 18:00:36 -0700
john stultz <johnstul@us.ibm.com> wrote:

> > 1) Does getrawmonotonic() satisfy hangcheck-timer?  What I mean is, will
> > it always return the wallclock nanoseconds even in the face of CPU speed
> > changes, suspend, udelay, or any other suspension of kernel operation?
> > Yes, I know this is a tougher standard than rdtsc(), but this is what
> > hangcheck-timer wants.  rdtsc() at least satisfied udelay and PCI hangs.
> 
> getrawmonotonic() can be stalled and will wrap on some hardware (acpi pm
> timer wraps every 5 seconds).
> 

I am not sure which archs do you mean. But in any case,
getrawmonotonic() is not just a wrap around a call to rdtsc() (or acpi
pm timer read). It is based on the clock->raw_time, which is updated
every timer interrupt by the update_wall_time(). So even if underlying
timer wraps, it doesn't lead to getrawmonotonic() returning 0 sec.


Y

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  reply	other threads:[~2010-03-29 14:11 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
2010-03-28  2:08               ` Yury Polyanskiy
2010-03-29  1:00   ` john stultz
2010-03-29 14:11     ` Yury Polyanskiy [this message]
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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