On Tue, 5 Aug 2014, Sasha Levin wrote:
> I can easily trigger it by cranking up the cpu hotplug code. Just try to
> frequently offline and online cpus, it should reproduce quickly.
Thats what I thought.
The test was done with this fix applied right?
Subject: vmstat ondemand: Fix online/offline races
Do not allow onlining/offlining while the shepherd task is checking
for vmstat threads.
On offlining a processor do the right thing cancelling the vmstat
worker thread if it exista and also exclude it from the shepherd
process checks.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Index: linux/mm/vmstat.c
===================================================================
--- linux.orig/mm/vmstat.c 2014-07-30 09:35:54.602662306 -0500
+++ linux/mm/vmstat.c 2014-07-30 09:43:07.109037043 -0500
@@ -1317,6 +1317,7 @@ static void vmstat_shepherd(struct work_
{
int cpu;
+ get_online_cpus();
/* Check processors whose vmstat worker threads have been disabled */
for_each_cpu(cpu, cpu_stat_off)
if (need_update(cpu) &&
@@ -1325,6 +1326,7 @@ static void vmstat_shepherd(struct work_
schedule_delayed_work_on(cpu, &per_cpu(vmstat_work, cpu),
__round_jiffies_relative(sysctl_stat_interval, cpu));
+ put_online_cpus();
schedule_delayed_work(&shepherd,
round_jiffies_relative(sysctl_stat_interval));
@@ -1380,8 +1382,8 @@ static int vmstat_cpuup_callback(struct
break;
case CPU_DOWN_PREPARE:
case CPU_DOWN_PREPARE_FROZEN:
- if (!cpumask_test_and_set_cpu(cpu, cpu_stat_off))
- cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
+ cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
+ cpumask_clear_cpu(cpu, cpu_stat_off);
break;
case CPU_DOWN_FAILED:
case CPU_DOWN_FAILED_FROZEN:
--
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