svn commit: r225288 - stable/8/sys/kern
Attilio Rao
attilio at FreeBSD.org
Wed Aug 31 09:14:56 UTC 2011
Author: attilio
Date: Wed Aug 31 09:14:56 2011
New Revision: 225288
URL: http://svn.freebsd.org/changeset/base/225288
Log:
MFC r225057:
Fix a race that can happen when switching spinlocks in
callout_cpu_switch() and curthread is preempted.
Modified:
stable/8/sys/kern/kern_timeout.c
Directory Properties:
stable/8/sys/ (props changed)
stable/8/sys/amd64/include/xen/ (props changed)
stable/8/sys/cddl/contrib/opensolaris/ (props changed)
stable/8/sys/contrib/dev/acpica/ (props changed)
stable/8/sys/contrib/pf/ (props changed)
Modified: stable/8/sys/kern/kern_timeout.c
==============================================================================
--- stable/8/sys/kern/kern_timeout.c Wed Aug 31 08:44:45 2011 (r225287)
+++ stable/8/sys/kern/kern_timeout.c Wed Aug 31 09:14:56 2011 (r225288)
@@ -267,10 +267,17 @@ callout_cpu_switch(struct callout *c, st
MPASS(c != NULL && cc != NULL);
CC_LOCK_ASSERT(cc);
+ /*
+ * Avoid interrupts and preemption firing after the callout cpu
+ * is blocked in order to avoid deadlocks as the new thread
+ * may be willing to acquire the callout cpu lock.
+ */
c->c_cpu = CPUBLOCK;
+ spinlock_enter();
CC_UNLOCK(cc);
new_cc = CC_CPU(new_cpu);
CC_LOCK(new_cc);
+ spinlock_exit();
c->c_cpu = new_cpu;
return (new_cc);
}
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