Module Name: src
Committed By: rmind
Date: Wed Dec 30 23:49:59 UTC 2009
Modified Files:
src/sys/kern: kern_runq.c
Log Message:
sched_catchlwp: fix the case when other CPU might see curlwp->l_cpu != curcpu()
while LWP is finishing context switch. Should fix PR/42539, tested by mar...@.
To generate a diff of this commit:
cvs rdiff -u -r1.27 -r1.28 src/sys/kern/kern_runq.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_runq.c
diff -u src/sys/kern/kern_runq.c:1.27 src/sys/kern/kern_runq.c:1.28
--- src/sys/kern/kern_runq.c:1.27 Wed Oct 21 21:12:06 2009
+++ src/sys/kern/kern_runq.c Wed Dec 30 23:49:59 2009
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_runq.c,v 1.27 2009/10/21 21:12:06 rmind Exp $ */
+/* $NetBSD: kern_runq.c,v 1.28 2009/12/30 23:49:59 rmind Exp $ */
/*
* Copyright (c) 2007, 2008 Mindaugas Rasiukevicius <rmind at NetBSD org>
@@ -27,7 +27,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_runq.c,v 1.27 2009/10/21 21:12:06 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_runq.c,v 1.28 2009/12/30 23:49:59 rmind Exp $");
#include <sys/param.h>
#include <sys/kernel.h>
@@ -486,6 +486,17 @@
/* Grab the thread, and move to the local run queue */
sched_dequeue(l);
+
+ /*
+ * If LWP is still context switching, we may need to
+ * spin-wait before changing its CPU.
+ */
+ if (__predict_false(l->l_ctxswtch != 0)) {
+ u_int count;
+ count = SPINLOCK_BACKOFF_MIN;
+ while (l->l_ctxswtch)
+ SPINLOCK_BACKOFF(count);
+ }
l->l_cpu = curci;
ci_rq->r_ev_pull.ev_count++;
lwp_unlock_to(l, curspc->spc_mutex);
