From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Thu, 7 May 2009 12:37:08 +0200
Subject: [s390] appldata: vtimer bug with cpu hotplug
Message-id: 20090507103708.GA5241@redhat.com
O-Subject: [RHEL5 U4 PATCH 1/1] s390 - appldata: vtimer bug with cpu hotplug
Bugzilla: 497207
RH-Acked-by: Brian Maly <bmaly@redhat.com>
RH-Acked-by: Pete Zaitcev <zaitcev@redhat.com>

Description
============

mod_virt_timer() was used to modify/add cpu timers for cpus that were
set online. This resulted in a one-shot timer for every cpu that was
newly added or previously set offline, instead of an interval timer,
which broke the appldata vtime interval setup.

Solution: Work around by adding a new vtimer for cpus that get online,
before modifying it.

Bugzilla
=========

BZ 497207
https://bugzilla.redhat.com/show_bug.cgi?id=497207

Upstream status of the patch:
=============================

The patch is upstream as of git commit 43ae8a1b32735c662ba7ebf3509c4f670f75e3d5
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=43ae8a1b32735c662ba7ebf3509c4f670f75e3d5

Test status:
============

The patch has been tested and fixes the problem.
The fix has been verified by the IBM test department.

Please ACK.

With best regards,

	--Hans

diff --git a/arch/s390/appldata/appldata_base.c b/arch/s390/appldata/appldata_base.c
index 2e1bcba..5027ef3 100644
--- a/arch/s390/appldata/appldata_base.c
+++ b/arch/s390/appldata/appldata_base.c
@@ -538,13 +538,22 @@ void appldata_unregister_ops(struct appldata_ops *ops)
 static void
 appldata_online_cpu(int cpu)
 {
+	u64 per_cpu_interval;
+
 	init_virt_timer(&per_cpu(appldata_timer, cpu));
 	per_cpu(appldata_timer, cpu).function = appldata_timer_function;
 	per_cpu(appldata_timer, cpu).data = (unsigned long)
 		&appldata_work;
 	atomic_inc(&appldata_expire_count);
 	spin_lock(&appldata_timer_lock);
-	__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
+	if (appldata_timer_active) {
+		per_cpu_interval = (u64) (appldata_interval * 1000 /
+					  num_online_cpus()) * TOD_MICRO;
+		per_cpu(appldata_timer, cpu).expires = per_cpu_interval;
+		smp_call_function_on(add_virt_timer_periodic,
+				     &per_cpu(appldata_timer, cpu), 0, 1, cpu);
+		__appldata_vtimer_setup(APPLDATA_MOD_TIMER);
+	}
 	spin_unlock(&appldata_timer_lock);
 }