John Baldwin wrote:
On Tuesday 10 January 2006 07:37 pm, Scott Long wrote:
scottl 2006-01-11 00:37:13 UTC
FreeBSD src repository
Modified files:
sys/kern subr_taskqueue.c
Log:
The interlock in taskqueue_terminate() is completely wrong for taskqueues
that use spinlocks. Remove it for now.
Eh? It's waiting for the wakeup that comes from kthread_exit() after the
thread has exited which is locked via the proc lock. Sleeping on the
taskqueue itself doesn't buy you anything. (In fact, it might sleep
forever.) The simplest solution might be to acquire the proc lock a lot
earlier before the taskqueue lock in this function so that you don't have to
acquire it while holding the taskqueue lock since that is what gives you
problems.
With the code the way it was, kthread_exit() in taskqueue_thread_loop
can wind up blocking on the proc lock while the lock is still held in
taskqueue_terminate. I don't know why this is actually a problem, but
turning on WITNESS to investigate revealed the immediate problem of
trying to grab the proc lock with a spinlock already held. The
interlock is really just a protection against drivers that don't
adequately quiesce themselves, so I removed it for now until we can
figure out something better.
Scott
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