Messages in this thread | | | Date | Wed, 9 Nov 2011 09:06:57 -0800 | From | Tejun Heo <> | Subject | Re: [PATCH] thp: reduce khugepaged freezing latency |
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Hello,
On Wed, Nov 09, 2011 at 08:59:25AM -0800, Tejun Heo wrote: > Freezer depends on the usual "set_current_state(INTERRUPTIBLE); check > freezing; schedule(); check freezing" construct and sends > INTERRUPTIBLE wake up after setting freezing state. The > synchronization hasn't been completely clear but recently been cleaned > up, so as long as freezing condition is tested after INTERRUPTIBLE is > set before going to sleep, the event won't go missing. > > Maybe we need a helper here, which would be named horribly - > schedule_timeout_interruptible_freezable(). (cc'ing Oleg) Oleg, maybe > we need schedule_timeout(@sleep_type) too?
Ah, crap, still waking up. Sorry about that. So, yes, there's a race condition above. You need to set TASK_INTERRUPTIBLE before testing freezing and use schedule_timeout() instead of schedule_timeout_interruptible(). Was getting confused with prepare_to_wait(). That said, why not use prepare_to_wait() instead?
Thanks.
-- tejun
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