linux-kernel - Re: [patch] fix the softlockup watchdog to actually work

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Date:	Thu, 19 Jul 2007 16:50:58 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	stable@...nel.org, Greg KH <greg@...ah.com>,
	Chris Wright <chrisw@...s-sol.org>
Subject: Re: [patch] fix the softlockup watchdog to actually work

* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Hm, or more specifically, why would that be a problem for softlockup? 
> Do you mean it doesn't measure time during ACPI idle?  That would just 
> make it trigger later than it would otherwise.

no, the return value after idling can be completely random on some 
boxes, on a 64-bit scale - triggering the softlockup watchdog randomly. 
(some boxes return random TSC values, etc.) Again, it's fine for the 
scheduler's purpose, that's why i named it sched_clock().

the proper clocksource use within the kernel is ktime_get() [or 
ktime_get_ts()]. Do not abuse sched_clock() for such things.

	Ingo
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