freebsd-5.4-stable panics

[John Baldwin]

On Friday 30 September 2005 11:25 am, Antoine Pelisse wrote:
> On 9/30/05, John Baldwin <jhb at 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 at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org