Date: Fri, 16 Mar 2001 14:31:18 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-alpha@FreeBSD.org Subject: RE: user process faulting on kernel address Message-ID: <XFMail.010316143118.jhb@FreeBSD.org> In-Reply-To: <15026.37378.477855.889651@grasshopper.cs.duke.edu>
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On 16-Mar-01 Andrew Gallatin wrote:
>
> When running a linuxthreads app which basically sits in a loop
> doing a pthread_create()/pthread_join() of a thread which just
> exits, I'll occasionally see a very interesting thing --
> the app dies on an instruction fault on a kernel address.
>
> Enabling the DEBUG printtrap() calls in trap yeilds this information:
>
> login:
> fatal user trap:
>
> trap entry = 0x2 (memory management fault)
> a0 = 0xfffffc0000418be0
> a1 = 0x1
> a2 = 0xffffffffffffffff
> pc = 0xfffffc0000418be0
> ra = 0x11ffbfc4
> curproc = 0xfffffe0006824cc0
> pid = 18788, comm = ex6
>
>
> Note that it is an instruction fault (a2 == -1) and the faulting
> address maps to the bottom of witness_exit:
>
> (kgdb) l *0xfffffc0000418be0
> 0xfffffc0000418be0 is in witness_exit (../../kern/kern_mutex.c:1262).
> 1257 m->mtx_line = line;
> 1258 m->mtx_file = file;
> 1259 p = curproc;
> 1260 MPASS(m->mtx_held.le_prev == NULL);
> 1261 LIST_INSERT_HEAD(&p->p_heldmtx, (struct mtx*)m, mtx_held);
> 1262 }
> 1263
> 1264 void
> 1265 witness_exit(struct mtx *m, int flags, const char *file, int line)
> 1266 {
>
>
> The $ra looks reasonable, it is at least a userspace stack address.
>
> I think somebody saw this a while ago, but I cannot find their
> message..
>
> Any ideas?
Weird. This might be related to the panics in witness_exit() during a
LIST_REMOVE of the same list. Perhaps we are on an interrupt stack, but there
should be some frames below witness_enter() if that were the case. :(
> Drew
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
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