xen: Add support for preemption

Add Xen support for preemption.  This is mostly a cleanup of existing
preempt_enable/disable calls, or just comments to explain the current
usage.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/arch/i386/xen/mmu.c b/arch/i386/xen/mmu.c
index bc49ef846203..f431cf14e644 100644
--- a/arch/i386/xen/mmu.c
+++ b/arch/i386/xen/mmu.c
@@ -38,6 +38,7 @@
  *
  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  */
+#include <linux/sched.h>
 #include <linux/highmem.h>
 #include <linux/bug.h>
 #include <linux/sched.h>
@@ -531,5 +532,7 @@ void xen_exit_mmap(struct mm_struct *mm)
         drop_mm_ref(mm);
         put_cpu();
 
+        spin_lock(&mm->page_table_lock);
         xen_pgd_unpin(mm->pgd);
+        spin_unlock(&mm->page_table_lock);
 }