__refrigerator() && saved task->state
From: Oleg Nesterov
Date: Wed Nov 13 2013 - 14:11:10 EST
Sorry for noise, but I am totally confused.
Could you please remind why __refrigerator() saves/restores
task->state?
I can see only one reason: set_freezable() kernel threads which
check kthread_should_stop() and do try_to_freeze() by hand.
But does this save/restore actually help?
For example kauditd_thread() looks obviously racy exactly because
try_to_freeze() can return in TASK_INTERRUPTIBLE state after
wake_up(kauditd_wait) was already called, we can miss an event.
At first glance it would be better to simply kill this logic? If
it was called with ->state != 0, the caller is going to schedule()
and it probably executes the wait_event-like code, in this case
it would me more safe to pretend the task got a spurious wakeup?
(as for kauditd_thread() in particular, it looks wrong in any
case, even kthread_should_stop() check doesn't look right, it
needs kthread_freezable_should_stop() afaics).
But I guess I missed something else...
Oleg.
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