From owner-freebsd-current  Sat Oct  6 21:50:15 2001
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Date: Sun, 7 Oct 2001 14:49:16 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
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To: Doug Barton <DougB@DougBarton.net>
Cc: <freebsd-current@FreeBSD.ORG>
Subject: Re: panic: blockable sleep lock (sx) allproc @ 
 /usr/local/src/sys/kern/kern_proc.c:212
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On Sat, 6 Oct 2001, Doug Barton wrote:

> Bruce Evans wrote:
>
> > This is a well-know bug in printf(9).  The TIOCCONS ioctl always gave
> > non-deterministic crashes.  Now it gives determinstic panics when
> > pintf() is called while sched_lock is held.  Work-around: don't use
> > anything that uses TIOCCONS (xconsole?).
>
> 	Yes, I'm using xconsole, and I find it very useful. How hard would it be
> to actually fix this? I'm still crashing fairly often with this same exact
> problem.

Thanks.  No one actually acknowledged my diagnosis of this bug before (I
don't use xconsole and haven't got around to trying it).

Is using xconsole significantly better than "tail -f /var/log/messages"?
Both have the problem of not being able to show any output if userland
can't run, but I think this problem would be only slightly larger for
syslogd and tail combined than for xconsole.  A fix would involve more
buffering in the kernel, or perhaps more elegantly, dropping TIOCCONS
and putting "tail -f"-like support in dmesg.

Bruce


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