Date: Sat, 28 Jul 2001 22:49:51 -1000 (HST) From: Vincent Poy <vince@oahu.WURLDLINK.NET> To: Ian Dowse <iedowse@maths.tcd.ie> Cc: <dillon@FreeBSD.ORG>, <current@FreeBSD.ORG>, <stable@FreeBSD.ORG> Subject: Re: SIGCHLD changes causing fault on nofault entry panics Message-ID: <20010728224835.Q48916-100000@oahu.WURLDLINK.NET> In-Reply-To: <200107271451.aa00148@salmon.maths.tcd.ie>
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On Fri, 27 Jul 2001, Ian Dowse wrote:
>
> The panics in exit1() that have been reported on -stable appear to
> be caused by these commits:
>
> REV:1.92.2.4 kern_exit.c 2001/07/25 17:21:46 dillon
> REV:1.72.2.7 kern_sig.c 2001/07/25 17:21:46 dillon
>
> MFC kern_exit.c 1.131, kern_sig.c 1.125 - bring SIGCHLD SIG_IGN signal
> handling in line with other operating systems.
>
> These probably correspond to similar panics seen in -current, but I
> haven't checked the details.
>
> In the vmcore I just got, the panic occurred in the following
> fragment in exit1(), when dereferencing p_sigacts (which is
> p_procsig->ps_sigacts). I guess there is a race here if the parent
> is exiting or something?
>
> + if ((p->p_pptr->p_procsig->ps_flag & PS_NOCLDWAIT)
> + || p->p_pptr->p_sigacts->ps_sigact[_SIG_IDX(SIGCHLD)] == SIG_IGN) {
>
> Matt, I will just back out these changes from RELENG_4 shortly
> until the issue is resolved. The change was non-essential and quite
> contained, so it's probably better than waiting for a fix.
>
> Ian
The problem seems to cause the following panic in vm_glue.c and nd
kern_lock.c as well.
Jul 28 21:29:40 pele /boot/kernel/kernel: lock order reversal
Jul 28 21:29:40 pele /boot/kernel/kernel: lock order reversal
Jul 28 21:29:40 pele /boot/kernel/kernel: 1st 0xd92fea9c process lock @
/usr/src/sys/vm/vm_glue.c:469
Jul 28 21:29:40 pele /boot/kernel/kernel: 1st 0xd92fea9c process lock @
/usr/src/sys/vm/vm_glue.c:469
Jul 28 21:29:40 pele /boot/kernel/kernel: 2nd 0xc118dfb0 lockmgr interlock
@ /usr/src/sys/kern/kern_lock.c:239
Jul 28 21:29:40 pele /boot/kernel/kernel: 2nd 0xc118dfb0 lockmgr interlock
@ /usr/src/sys/kern/kern_lock.c:239
panic: recurse
Debugger ("panic")
Stopped at Debugger+0x44: push1 %ebx
db>
and then it just hangs solid here.
Cheers,
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