cpu hotplug: fix ksoftirqd termination on cpu hotplug with naughty realtime process
Fix ksoftirqd termination on cpu hotplug with naughty real time process.
Assuming the following case:
- Try to hot remove CPU2 from CPU1.
- There is a real time process on CPU2, and that process doesn't sleep at all.
- That rt process and ksoftirqd/2 is migrated to the CPU0
Then ksoftirqd/2 can't stop becasue that rt process runs everlastingly on
CPU0, and CPU1 waiting the ksoftirqd/2's termination hangs up. To fix this
problem, set the priority of ksoftirqd/2 to max one before kthread_stop().
[akpm@linux-foundation.org: fix warning]
Signed-off-by: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 73217a9..8de2677 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -614,12 +614,16 @@
kthread_bind(per_cpu(ksoftirqd, hotcpu),
any_online_cpu(cpu_online_map));
case CPU_DEAD:
- case CPU_DEAD_FROZEN:
+ case CPU_DEAD_FROZEN: {
+ struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };
+
p = per_cpu(ksoftirqd, hotcpu);
per_cpu(ksoftirqd, hotcpu) = NULL;
+ sched_setscheduler(p, SCHED_FIFO, ¶m);
kthread_stop(p);
takeover_tasklets(hotcpu);
break;
+ }
#endif /* CONFIG_HOTPLUG_CPU */
}
return NOTIFY_OK;