Date: Sat, 23 Aug 2008 00:03:43 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: kevinxlinuz <kevinxlinuz@163.com> Subject: Re: [BUG] I think sleepqueue need to be protected in sleepq_broadcast Message-ID: <200808230003.44081.jhb@freebsd.org> In-Reply-To: <11617822.2511219426408994.JavaMail.coremail@bj163app64.163.com> References: <11617822.2511219426408994.JavaMail.coremail@bj163app64.163.com>
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On Friday 22 August 2008 01:33:28 pm kevinxlinuz wrote:
> Hi,
> I'm looking in the problem ( amd64/124200: kernel panic on mutex sleepq
> chain).It troubles me for a long time.I add a KASSERT in sleepq_broadcast()
> to check the sleepqueue's wait channel.At last it turn out that the
> sleepqueue's wait channel was changed before sleepq_resume_thread(). In
> sleepq_lookup(),We can easily find sq->sq_wchan == wchan.But after a short
> time,the sq->sq_wchan nolonger equal with wchan,so I think it was changed
> by other threads.
The sleepq chain lock is already held for all of sleepq_broadcast() by the
caller (see wakeup() and cv_broadcastpri()). That said, I don't have any
other good ideas for the panic you are seeing. Do you have a crash dump? It
might be interesting to see what other thread is using that sleep queue.
> sleepq_broadcast(void *wchan, int flags, int pri, int queue)
> {
> struct sleepqueue *sq;
> struct thread *td;
> int wakeup_swapper;
>
> CTR2(KTR_PROC, "sleepq_broadcast(%p, %d)", wchan, flags);
> KASSERT(wchan != NULL, ("%s: invalid NULL wait channel",
> __func__)); MPASS((queue >= 0) && (queue < NR_SLEEPQS));
> sq = sleepq_lookup(wchan);
> if (sq == NULL)
> return (0);
> KASSERT(sq->sq_type == (flags & SLEEPQ_TYPE),
> ("%s: mismatch between sleep/wakeup and cv_*", __func__));
>
> /* Resume all blocked threads on the sleep queue. */
> wakeup_swapper = 0;
> while (!TAILQ_EMPTY(&sq->sq_blocked[queue])) {
> td = TAILQ_FIRST(&sq->sq_blocked[queue]);
> thread_lock(td);
> /* test */
> KASSERT(sq->sq_wchan == wchan,
> ("%s:mismatch between wchan and sq_wchan in
> sq",__func__)); /* I find the panic here */
> if (sleepq_resume_thread(sq, td, pri))
> wakeup_swapper = 1;
> thread_unlock(td);
> }
> return (wakeup_swapper);
> }
>
> Thanks,
> kevin 2008/08/23
>
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--
John Baldwin
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