linux-kernel - [PATCH 1/1] vmstat-use-our-own-timer-events-fix

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Date:	Tue,  8 May 2007 16:30:55 +0200 (CEST)
From:	Jiri Slaby <jirislaby@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	<linux-pm@...ts.linux-foundation.org>,
	<linux-kernel@...r.kernel.org>
Subject: [PATCH 1/1] vmstat-use-our-own-timer-events-fix

Oleg Nesterov wrote:
> On 05/08, Oleg Nesterov wrote:
> >
> > On 05/08, Jiri Slaby wrote:
> >
> > This should not happen because we are doing cancel_rearming_delayed_work()
> > below, however:
> > 
> > > +       case CPU_DOWN_PREPARE:
> > > +       case CPU_DOWN_PREPARE_FROZEN:
> > > +               cancel_rearming_delayed_work(&per_cpu(vmstat_work, cpu));
> > > +               per_cpu(vmstat_work, cpu).work.func = NULL;
> > > +       case CPU_DOWN_FAILED:
> > > +       case CPU_DOWN_FAILED_FROZEN:
> > > +               start_cpu_timer(cpu);
> > 
> > we need a "break;" before "case CPU_DOWN_FAILED", otherwise we re-start
> > vmstat_update() immediately.
> > 
> > This is a bug, but I am not sure is this the only problem.
> 
> In case I was not clear, this _can_ explain the problem. Because an extra
> start_cpu_timer() (due to missed "break;") re-initializes dwork, and clears
> _PENDING.

Yes, it helped, thanks. If no objections, please apply the patch below.

--

vmstat-use-our-own-timer-events-fix

add missing break

Cc: Christoph Lameter <clameter@....com>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
Signed-off-by: Jiri Slaby <jirislaby@...il.com>

---
commit e0fe3cf4776a3c16ac7625ce9eae75ea42eb9b4e
tree c9a4277860e2cea03911b3d73c9386c9284d991b
parent b1034323f7e57642eee59a0f5e77c50bc26982c5
author Jiri Slaby <jirislaby@...il.com> Tue, 08 May 2007 16:25:28 +0200
committer Jiri Slaby <jirislaby@...il.com> Tue, 08 May 2007 16:25:28 +0200

 mm/vmstat.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 709e2f0..fac05e8 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -677,6 +677,7 @@ static int __cpuinit vmstat_cpuup_callback(struct notifier_block *nfb,
 	case CPU_DOWN_PREPARE_FROZEN:
 		cancel_rearming_delayed_work(&per_cpu(vmstat_work, cpu));
 		per_cpu(vmstat_work, cpu).work.func = NULL;
+		break;
 	case CPU_DOWN_FAILED:
 	case CPU_DOWN_FAILED_FROZEN:
 		start_cpu_timer(cpu);
-
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