| commit | 7bb8fd4ee497a34c68e35d259a20d98cbad7fc94 | |
| author | Yang Xiaowei <xiaowei.yang@intel.com> | |
| Wed, 9 Sep 2009 19:44:52 +0000 (9 12:44 -0700) | ||
| committer | Greg Kroah-Hartman <gregkh@suse.de> | |
| Mon, 5 Oct 2009 16:31:45 +0000 (5 09:31 -0700) | ||
| tree | 81e7418ff8521f813125e1f7b6b4a15704118715 | treesnapshot (tar.gz zip) |
| parent | 64aa234c396c3f595bc08aed93fd753102a0a0ec | commitdiff |
xen: use stronger barrier after unlocking lock
commit 2496afbf1e50c70f80992656bcb730c8583ddac3 upstream.
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 <xiaowei.yang@intel.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
commit 2496afbf1e50c70f80992656bcb730c8583ddac3 upstream.
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 <xiaowei.yang@intel.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| arch/x86/xen/spinlock.c | diffblobblamehistory |