diff options
| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2011-09-30 15:52:14 +0200 |
|---|---|---|
| committer | Clark Williams <williams@redhat.com> | 2012-04-13 11:01:39 -0500 |
| commit | b8134b027ffc884951edaf92ba9935ed6ca2d6bf (patch) | |
| tree | c2002a03d12a3b049cfc305194ee45ce71508851 | |
| parent | 3e01082efd38048231bbffe71b54b98211acf492 (diff) | |
softirq: Fix unplug deadlock
If ksoftirqd gets woken during hot-unplug, __thread_do_softirq() will
call pin_current_cpu() which will block on the held cpu_hotplug.lock.
Moving the offline check in __thread_do_softirq() before the
pin_current_cpu() call doesn't work, since the wakeup can happen
before we mark the cpu offline.
So here we have the ksoftirq thread stuck until hotplug finishes, but
then the ksoftirq CPU_DOWN notifier issues kthread_stop() which will
wait for the ksoftirq thread to go away -- while holding the hotplug
lock.
Sort this by delaying the kthread_stop() until CPU_POST_DEAD, which is
outside of the cpu_hotplug.lock, but still serialized by the
cpu_add_remove_lock.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: rostedt <rostedt@goodmis.org>
Cc: Clark Williams <williams@redhat.com>
Link: http://lkml.kernel.org/r/1317391156.12973.3.camel@twins
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | kernel/softirq.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/kernel/softirq.c b/kernel/softirq.c index 5741cf7ddb17..d1fdb9155d44 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -1078,9 +1078,8 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb, int hotcpu = (unsigned long)hcpu; struct task_struct *p; - switch (action) { + switch (action & ~CPU_TASKS_FROZEN) { case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: p = kthread_create_on_node(run_ksoftirqd, hcpu, cpu_to_node(hotcpu), @@ -1093,19 +1092,16 @@ static int __cpuinit cpu_callback(struct notifier_block *nfb, per_cpu(ksoftirqd, hotcpu) = p; break; case CPU_ONLINE: - case CPU_ONLINE_FROZEN: wake_up_process(per_cpu(ksoftirqd, hotcpu)); break; #ifdef CONFIG_HOTPLUG_CPU case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: if (!per_cpu(ksoftirqd, hotcpu)) break; /* Unbind so it can run. Fall thru. */ kthread_bind(per_cpu(ksoftirqd, hotcpu), cpumask_any(cpu_online_mask)); - case CPU_DEAD: - case CPU_DEAD_FROZEN: { + case CPU_POST_DEAD: { static const struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 }; |