Bug 482918

Summary: do_timer_interrupt() does not acquire or release xtime_lock
Product: Red Hat Enterprise Linux 4 Reporter: Prarit Bhargava <prarit>
Component: kernelAssignee: Prarit Bhargava <prarit>
Status: CLOSED NOTABUG QA Contact: Martin Jenner <mjenner>
Severity: medium Docs Contact:
Priority: medium    
Version: 4.8CC: bmaly, peterm, vgoyal
Target Milestone: rc   
Target Release: ---   
Hardware: i386   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2009-01-29 13:56:15 UTC Type: ---
Regression: --- Mount Type: ---
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Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description Prarit Bhargava 2009-01-28 19:52:28 UTC 
Description of problem:

do_timer_interrupt does not acquire or release the xtime_lock (which is a sequential lock) when servicing the timer interrupt.  The rest of the i386 timing code does use the lock and we've imported a lot of code into RHEL4 which uses the xtime_lock.

Version-Release number of selected component (if applicable):  2.6.9-80.el4

I can almost guarantee that some of the timing instability is due to this missing lock.

This issue, however, maybe moot.  RHEL4 is almost at the end of its life, and I'm not sure we should change this behavior now.  OTOH, as mentioned, using the lock in do_timer_interrupt() will certainly increase stability in gettimeofday calls, system time, etc.

P.