Deadlock [PATCH]

[Peter Holm]

I have tracked down, what I belive to be the cause of several
deadlock situations I have encountered, like
http://people.freebsd.org/~pho/stress/cons40.html.

The problem seems to be the 4bsd scheduler, that does not preempt correctly.

I've included a patch that fixes the problem for me.
-- 
Peter Holm
-------------- next part --------------
--- sched_4bsd.c~	Sun Jun 15 16:57:17 2003
+++ sched_4bsd.c	Sun Aug 10 08:41:06 2003
@@ -448,7 +448,8 @@
 
 	ke->ke_sched->ske_cpticks++;
 	kg->kg_estcpu = ESTCPULIM(kg->kg_estcpu + 1);
-	if ((kg->kg_estcpu % INVERSE_ESTCPU_WEIGHT) == 0) {
+	if (((kg->kg_estcpu + 1) % INVERSE_ESTCPU_WEIGHT) == 0) {
+		curthread->td_flags |= TDF_NEEDRESCHED;
 		resetpriority(kg);
 		if (td->td_priority >= PUSER)
 			td->td_priority = kg->kg_user_pri;