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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 martin@.
This commit is contained in:
rmind 2009-12-30 23:49:59 +00:00
parent ded5c676f3
commit 65265dedb7
1 changed files with 13 additions and 2 deletions
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15
sys/kern/kern_runq.c
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@ -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 @@ sched_catchlwp(struct cpu_info *ci)
/* 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);