path: root/lib/libsbuf
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authorJohn Baldwin <jhb@FreeBSD.org>2011-05-17 16:39:08 +0000
committerJohn Baldwin <jhb@FreeBSD.org>2011-05-17 16:39:08 +0000
commitf83e8b25c1ef10af62fabdd117aec0db71d33cc3 (patch)
tree124abfe51ae998feb5dfea7f9068230da29f857e /lib/libsbuf
parent6c63a20b4939d86a62970f62be6e78a055da0df2 (diff)
Fix a race in the SMP rendezvous code. Specifically, the write by the
last CPU to to finish the rendezvous action may become visible to different CPUs at different times. As a result, the CPU that initiated the rendezvous may exit the rendezvous and drop the lock allowing another rendezvous to be initiated on the same CPU or a different CPU. In that case the exit sentinel may be cleared before all CPUs have noticed causing those CPUs to hang forever. Workaround this by using a generation count to notice when this race occurs and to exit the rendezvous in that case. The problem was independently diagnosted by mlaier@ and avg@ as well. Submitted by: neel Reviewed by: avg, mlaier Obtained from: NetApp MFC after: 1 week
Notes: svn path=/head/; revision=222032
Diffstat (limited to 'lib/libsbuf')
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