Attachment 291065 Details for Bug 427998 – xen-unstable.hg 10327:c230dbe793d6 backported to 2.6.9-67.EL

[patch] xen-unstable.hg 10327:c230dbe793d6 backported to 2.6.9-67.EL

xen-unstable-10327-c230dbe793d6 (text/plain), 1.90 KB, created by Ian Campbell on 2008-01-08 16:22:39 UTC

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Creator: Ian Campbell

Created: 2008-01-08 16:22:39 UTC

Size: 1.90 KB

patch

obsolete

># HG changeset patch
># User kaf24@firebug.cl.cam.ac.uk
># Node ID c230dbe793d623d67ca1d486c0c1a8db5c7cab94
># Parent  34ff26fb2240b836057de452abdd740e8122a584
>[LINUX] Fix interaction between idle loop and RCU subsystem.
>
>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@uk.ibm.com>
>xen-unstable changeset: 10327:c230dbe793d623d67ca1d486c0c1a8db5c7cab94
>xen-unstable date: Mon Jun 12 14:17:05 2006 +0100
>
>Index: linux-2.6.9-67.0.1.EL/arch/i386/kernel/time-xen.c
>===================================================================
>--- linux-2.6.9-67.0.1.EL.orig/arch/i386/kernel/time-xen.c	2008-01-02 15:50:55.000000000 +0000
>+++ linux-2.6.9-67.0.1.EL/arch/i386/kernel/time-xen.c	2008-01-02 15:55:28.000000000 +0000
>@@ -860,12 +860,19 @@
> 	unsigned int cpu = smp_processor_id();
> 	unsigned long j;
> 
>-	/* We must do this /before/ checking rcu_pending(). */
> 	cpu_set(cpu, nohz_cpu_mask);
>+
>+	/* See matching smp_mb in rcu_start_batch in rcupdate.c.  These mbs  */
>+	/* ensure that if __rcu_pending (nested in rcu_needs_cpu) fetches a  */
>+	/* value of rcp->cur that matches rdp->quiescbatch and allows us to  */
>+	/* stop the hz timer then the cpumasks created for subsequent values */
>+	/* of cur in rcu_start_batch are guaranteed to pick up the updated   */
>+	/* nohz_cpu_mask and so will not depend on this cpu.                 */
>+
> 	smp_mb();
> 
> 	/* Leave ourselves in tick mode if rcu or softirq pending. */
>-	if (rcu_pending(cpu) || local_softirq_pending()) {
>+	if (rcu_needs_cpu(cpu) || local_softirq_pending()) {
> 		cpu_clear(cpu, nohz_cpu_mask);
> 		j = jiffies + 1;
> 	} else {

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Attachments on bug 427998: 291063 | 291064 | 291065 | 291066