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kern/45090: missing callout_ack in sleepq code
>Synopsis: missing callout_ack in sleepq code
>Arrival-Date: Tue Jun 21 06:50:00 +0000 2011
>Originator: David A. Holland
>Release: NetBSD 5.99 (20110620)
When you call cv_timedwait or cv_timedwait_sig, it calls sleepq_block
with a nonzero timeout. This in turn uses a callout,
curlwp->l_timeout_ch, to call sleepq_timeout later.
Meanwhile, from reading the callout code, it appears that one is
supposed to call callout_ack() to clear the CALLOUT_INVOKING flag; but
nothing in the sleepq code does so, so ->l_timeout_ch's flags will
contain CALLOUT_INVOKING even long after a timeout has taken place.
This in turn can lead one down the garden path when trying to debug
timeouts that apparently aren't timing out. I don't think it has any
more serious effects than that though.
Should be sufficient to add callout_ack to sleepq_timeout, although
someone more familiar with the locking model than me should check to
make sure that won't deadlock miserably.
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