[Xen-devel] [PATCH] backport rcu_needs_cpu and call it from stop_hz_timer

[Harry Butterworth <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

I have now tested this against xen-testing 9735.  Without the patch, and
with a domU kernel configured with CONFIG_DEBUG_SOFTLOCKUP disabled
(this debug code masks the problem), and smp and cpu hotplug enabled, a
script which does lots of cpu hotplug/removal will hang (cpu
hotplug/removal stresses the RCU synchronize_sched function).  With the
patch, the script doing cpu hotplug/removal runs for as long as I have
let it so far (thousands of hotplugs).

Please apply.

Signed-off-by: Harry Butterworth <butterwo@xxxxxxxxxx>

On Fri, 2006-06-09 at 21:21 +0100, Harry Butterworth wrote:
> There is a problem with the current implementation of stop_hz_timer in
> arch/i386/kernel/time-xen.c where the hz timer can be stopped on a CPU
> which has RCU callbacks pending.
> 
> This patch backports a new RCU API created to fix this problem for the
> s390 implementation of stop_hz_timer and also updates the time-xen.c
> implementation of stop_hz_timer to call the new API.
> 
> Signed-off-by: Harry Butterworth <butterwo@xxxxxxxxxx>
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel

Attachment: rcu_needs_cpu.patch
Description: Text Data

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