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Date: Sun, 7 Aug 2005 21:59:13 +0200
From: Antoine Pelisse <apelisse@gmail.com>
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Subject: Fix for some stress panics
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http://people.freebsd.org/~pho/stress/log/cons149.html
http://people.freebsd.org/~pho/stress/log/cons130.html

I've been working on this panic today (the two are obviously=20
the same) and here is a patch to fix it:
--- sys/kern/kern_proc.c.orig Mon Apr 18 04:10:36 2005
+++ sys/kern/kern_proc.c Sun Aug 7 21:18:03 2005
@@ -884,10 +884,8 @@
_PHOLD(p);
FOREACH_THREAD_IN_PROC(p, td) {
fill_kinfo_thread(td, &kinfo_proc);
- PROC_UNLOCK(p);
error =3D SYSCTL_OUT(req, (caddr_t)&kinfo_proc,
sizeof(kinfo_proc));
- PROC_LOCK(p);
if (error)
break;
}

As a matter of fact, if td is removed from the list through thread_unlink=
=20
while
the mutex is released and the next thread is removed just after, the FOREAC=
H=20

is looping through an unlinked list where the td_ksegrp has been set to NUL=
L=20

by thread_exit.
If we absolutely have to release the lock, then it's probably safer to chec=
k=20
if=20
td_ksegroup !=3D NULL in the fill_kinfo_thread function.

Regards,=20
Antoine Pelisse.