diff options
Diffstat (limited to 'kernel/smpboot.c')
| -rw-r--r-- | kernel/smpboot.c | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 3a0415803b09..552e154fc77e 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -122,7 +122,45 @@ static int smpboot_thread_fn(void *data) } if (kthread_should_park()) { + /* + * Serialize against wakeup. If we take the lock first, + * wakeup is skipped. If we run later, we observe, + * TASK_RUNNING update from wakeup path, before moving + * forward. This helps avoid the race, where wakeup + * observes TASK_INTERRUPTIBLE, and also observes + * the TASK_PARKED in kthread_parkme() before updating + * task state to TASK_RUNNING. In this case, kthread + * gets parked in TASK_RUNNING state. This results + * in panic later on in kthread_unpark(), as it sees + * KTHREAD_IS_PARKED flag set but fails to rebind the + * kthread, due to it being not in TASK_PARKED state. + * + * Control thread Hotplug Thread + * + * kthread_park() + * set KTHREAD_SHOULD_PARK + * smpboot_thread_fn() + * set_current_state( + * TASK_INTERRUPTIBLE); + * kthread_parkme() + * + * wake_up_process() + * + * raw_spin_lock_irqsave(&p->pi_lock, flags); + * if (!(p->state & state)) + * goto out; + * + * __set_current_state( + * TASK_PARKED); + * + * if (p->on_rq && ttwu_remote(p, wake_flags)) + * ttwu_remote() + * p->state = TASK_RUNNING; + * schedule(); + */ + raw_spin_lock(¤t->pi_lock); __set_current_state(TASK_RUNNING); + raw_spin_unlock(¤t->pi_lock); preempt_enable(); if (ht->park && td->status == HP_THREAD_ACTIVE) { BUG_ON(td->cpu != smp_processor_id()); |