Date: Tue, 17 May 2011 16:39:08 +0000 (UTC) From: John Baldwin <jhb@FreeBSD.org> To: cvs-src-old@freebsd.org Subject: cvs commit: src/sys/kern subr_smp.c Message-ID: <201105171639.p4HGdTMP097163@repoman.freebsd.org>
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jhb 2011-05-17 16:39:08 UTC FreeBSD src repository Modified files: sys/kern subr_smp.c Log: SVN rev 222032 on 2011-05-17 16:39:08Z by jhb 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 Revision Changes Path 1.226 +48 -15 src/sys/kern/subr_smp.c
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