Date: Fri, 30 Sep 2005 13:10:01 -0400 From: John Baldwin <jhb@FreeBSD.org> To: freebsd-hackers@freebsd.org, Antoine Pelisse <apelisse@gmail.com> Cc: Robert Watson <rwatson@freebsd.org> Subject: Re: freebsd-5.4-stable panics Message-ID: <200509301310.03124.jhb@FreeBSD.org> In-Reply-To: <61c746830509300825s5ad197fbt908267d54f1b7b8f@mail.gmail.com> References: <da4a53d805092310237d732554@mail.gmail.com> <61c746830509300824g2f368d26pcc500403fe319b3b@mail.gmail.com> <61c746830509300825s5ad197fbt908267d54f1b7b8f@mail.gmail.com>
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On Friday 30 September 2005 11:25 am, Antoine Pelisse wrote: > On 9/30/05, John Baldwin <jhb@freebsd.org> wrote: > > On Friday 30 September 2005 05:24 am, Antoine Pelisse wrote: > > > Hi Robert, > > > I don't think your patch is correct, the total linked list can be > > > broken > > > > > > while the lock is released, thus just passing the link may not be > > > enough I have submitted a PR[1] for this a month ago but nobody took > > > care of it yet Regards, > > > Antoine Pelisse > > > > > > [1] http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/84684 > > > > I think this patch looks ok. Robert, can you get the original panic on > > this > > thread tested against this patch? > > I had a small program which could reproduce this panic in 10 seconds, it > was basically creating empty threads and calling kvm_getprocs() in the same > time. Anyway the patch was able to stop the program from panicing. > The panic is also reproducible in RELENG_6 and HEAD IIRC. 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 Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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