From: Yang Xiaowei Date: Wed, 9 Sep 2009 19:44:52 +0000 (-0700) Subject: xen: use stronger barrier after unlocking lock X-Git-Tag: v2.6.32-rc1~704^2~1 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2496afbf1e50c70f80992656bcb730c8583ddac3;p=pandora-kernel.git xen: use stronger barrier after unlocking lock We need to have a stronger barrier between releasing the lock and checking for any waiting spinners. A compiler barrier is not sufficient because the CPU's ordering rules do not prevent the read xl->spinners from happening before the unlock assignment, as they are different memory locations. We need to have an explicit barrier to enforce the write-read ordering to different memory locations. Because of it, I can't bring up > 4 HVM guests on one SMP machine. [ Code and commit comments expanded -J ] [ Impact: avoid deadlock when using Xen PV spinlocks ] Signed-off-by: Yang Xiaowei Signed-off-by: Jeremy Fitzhardinge --- Reading git-diff-tree failed