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Date: Tue, 4 Oct 2005 09:04:45 -0700 (PDT)
From: Don Lewis <truckman@FreeBSD.org>
To: rob@hudson-trading.com
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Cc: freebsd-hackers@FreeBSD.org, mikep@hudson-trading.com,
	jason@hudson-trading.com
Subject: Re: freebsd-5.4-stable panics
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On  3 Oct, Rob Watt wrote:
>> It turns out that the sysctl buffer is already wired in one of the two
>> cases
>> that this function is called, so I moved the wiring up to the upper
> layer
>> in
>> the other case and cut out a bunch of the locking gymnastics as a
> result.
>> Can you try this patch?
>>
>> Index: kern_proc.c
>> ===================================================================
>> RCS file: /usr/cvs/src/sys/kern/kern_proc.c,v
>> retrieving revision 1.231
>> diff -u -r1.231 kern_proc.c
>> --- kern_proc.c 27 Sep 2005 18:03:15 -0000 1.231
>> +++ kern_proc.c 30 Sep 2005 17:04:57 -0000
>> @@ -875,22 +875,16 @@
>>
>> if (flags & KERN_PROC_NOTHREADS) {
>> fill_kinfo_proc(p, &kinfo_proc);
>> - PROC_UNLOCK(p);
>> error = SYSCTL_OUT(req, (caddr_t)&kinfo_proc,
>> sizeof(kinfo_proc));
>> - PROC_LOCK(p);
>> } else {
>> - _PHOLD(p);
>> FOREACH_THREAD_IN_PROC(p, td) {
>> fill_kinfo_thread(td, &kinfo_proc);
>> - PROC_UNLOCK(p);
>> error = SYSCTL_OUT(req, (caddr_t)&kinfo_proc,
>> sizeof(kinfo_proc));
>> - PROC_LOCK(p);
>> if (error)
>> break;
>> }
>> - _PRELE(p);
>> }
>> PROC_UNLOCK(p);
>> if (error)
>> @@ -932,6 +926,9 @@
>> if (oid_number == KERN_PROC_PID) {
>> if (namelen != 1)
>> return (EINVAL);
>> + error = sysctl_wire_old_buffer(req, 0);
>> + if (error)
>> + return (error);
>> p = pfind((pid_t)name[0]);
>> if (!p)
>> return (ESRCH);
> 
> John,
> 
> We tried this patch and were able to run our simulations (and top) for 3
> days straight without crashing. Since we were panicking every 3-6 hours
> before when running top, this seems to have fixed the problem.
> 
> We noticed the patches from Don Lewis, but have not tested them yet. We
> weren't sure if we could just apply those patches against 6.0-BETA5, or
> whether we should wait for them to be MFC'd.

I haven't tried applying my patch to RELENG_5 yet, but hope to do so in
the next few days in preparation for doing a MFC.  If any changes are
required, I can send you a copy of the patch.