From: Lucio De Re <lucio@proxima.alt.za>
To: 9fans@9fans.net
Subject: Re: [9fans] That deadlock, again
Date: Thu, 18 Nov 2010 07:50:49 +0200 [thread overview]
Message-ID: <215c4028dc0c6d0cdcda7fd23830bc70@proxima.alt.za> (raw)
> one could move:
>
> up->qpc = getcallerpc(&q);
>
> from qlock() before the lock(&q->use); so we can see from where that
> qlock gets called that hangs the exportfs call, or add another magic
> debug pointer (qpctry) to the proc stucture and print it in dumpaproc().
Cinap, I tried your debugging code and got an odd panic at boot time.
Consistently:
panic: kernel fault: no user process pc=0xf01e739e addr=0x000009e8
Having a look with acid, this seems to be caused by an attempt at
setting the debug PC (your "up->qpctry") at a time when "up" has no
value yet.
Strangely, later in the qlock() code "up" is checked and a panic
issued if zero. I'm missing something here: it is possible to execute
this code
/sys/src/9/port/qlock.c:29,37 (more or less)
lock(&q->use);
rwstats.qlock++;
if(!q->locked) {
q->locked = 1;
unlock(&q->use);
return;
}
which is immediately followed by
if(up == 0)
panic("qlock");
If "up" is nil, but it looks like a bit of a one-way operation.
Anyway, I have moved the assignment to "qpctry" to after "up" is
tested. Let's see what happens. I'll have to get back to you once
the system is back up.
++L
next reply other threads:[~2010-11-18 5:50 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-18 5:50 Lucio De Re [this message]
2010-11-18 5:53 ` erik quanstrom
2010-11-18 8:11 ` Lucio De Re
2010-11-18 8:35 ` cinap_lenrek
2010-11-18 9:20 ` cinap_lenrek
2010-11-18 10:48 ` Lucio De Re
2010-11-18 15:10 ` erik quanstrom
2010-11-18 16:46 ` erik quanstrom
2010-11-18 18:01 ` Lucio De Re
2010-11-18 18:29 ` C H Forsyth
2010-11-18 18:23 ` Lucio De Re
2010-11-18 18:33 ` Lucio De Re
2010-11-18 18:43 ` erik quanstrom
2010-11-18 18:54 ` erik quanstrom
2010-11-18 19:01 ` Lucio De Re
2010-11-18 19:27 ` Lucio De Re
2010-11-18 18:03 ` Lucio De Re
2010-11-18 5:57 ` Lucio De Re
-- strict thread matches above, loose matches on Subject: below --
2010-11-16 4:21 lucio
2010-11-16 4:40 ` erik quanstrom
2010-11-16 5:03 ` lucio
2010-11-16 5:11 ` cinap_lenrek
2010-11-16 5:18 ` lucio
2010-11-16 5:28 ` cinap_lenrek
2010-11-16 6:47 ` Lucio De Re
2010-11-16 13:53 ` erik quanstrom
2010-11-16 18:03 ` lucio
2010-11-17 4:08 ` Lucio De Re
2010-11-17 4:18 ` erik quanstrom
2010-11-17 4:37 ` Lucio De Re
2010-11-17 4:43 ` erik quanstrom
2010-11-17 5:22 ` cinap_lenrek
2010-11-17 6:45 ` Lucio De Re
2010-11-17 7:03 ` Lucio De Re
2010-11-17 7:09 ` erik quanstrom
2010-11-17 5:33 ` cinap_lenrek
2010-11-17 6:48 ` Lucio De Re
2010-11-17 7:03 ` erik quanstrom
2010-11-17 14:40 ` Russ Cox
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