From: Yury Polyanskiy <ypolyans@princeton.edu>
Date: Mon, 24 May 2010 21:33:02 +0000 (-0700)
Subject: hangcheck-timer: fix x86_32 bugs
X-Git-Tag: v2.6.35-rc1~343
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=940370fc86b920b51a34217a1facc3e9e97c2456;p=pandora-kernel.git

hangcheck-timer: fix x86_32 bugs

drivers/char/hangcheck-timer.c is doubly broken.  When the overflown value
of TIMER_FREQ is abnormally low, it spams the syslog with KERN_CRIT
messages "Hangcheck: hangcheck value past margin!" But whether it happens
or not depends on HZ and lpj in a complex way.  People have hit it
occasionally as far as google search can tell.

First, the following line overflows unsigned long:

# define TIMER_FREQ (HZ*loops_per_jiffy)

Second, and more importantly, loops_per_jiffy has little to do with the
con= version from the the time scale of get_cycles() (aka rdtsc) to the
time scale of jiffies.

The attached patch resolves both of the problems.

Acked-by: Joel Becker <joel.becker@oracle.com>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Jan Glauber <jan.glauber@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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