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, 6 insertions, 5 deletions

diff --git a/arch/i386/xen/multicalls.c b/arch/i386/xen/multicalls.c
index 869f9833f08f..d4015a9ed46c 100644
--- a/arch/i386/xen/multicalls.c
+++ b/arch/i386/xen/multicalls.c
@@ -20,6 +20,7 @@
  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  */
 #include <linux/percpu.h>
+#include <linux/hardirq.h>
 
 #include <asm/xen/hypercall.h>
 
@@ -39,10 +40,12 @@ DEFINE_PER_CPU(unsigned long, xen_mc_irq_flags);
 
 void xen_mc_flush(void)
 {
-        struct mc_buffer *b = &get_cpu_var(mc_buffer);
+        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
         int ret = 0;
         unsigned long flags;
 
+        BUG_ON(preemptible());
+
         /* Disable interrupts in case someone comes in and queues
            something in the middle */
         local_irq_save(flags);
@@ -60,7 +63,6 @@ void xen_mc_flush(void)
         } else
                 BUG_ON(b->argidx != 0);
 
-        put_cpu_var(mc_buffer);
         local_irq_restore(flags);
 
         BUG_ON(ret);
@@ -68,10 +70,11 @@ void xen_mc_flush(void)
 
 struct multicall_space __xen_mc_entry(size_t args)
 {
-        struct mc_buffer *b = &get_cpu_var(mc_buffer);
+        struct mc_buffer *b = &__get_cpu_var(mc_buffer);
         struct multicall_space ret;
         unsigned argspace = (args + sizeof(u64) - 1) / sizeof(u64);
 
+        BUG_ON(preemptible());
         BUG_ON(argspace > MC_ARGS);
 
         if (b->mcidx == MC_BATCH ||
@@ -83,7 +86,5 @@ struct multicall_space __xen_mc_entry(size_t args)
         ret.args = &b->args[b->argidx];
         b->argidx += argspace;
 
-        put_cpu_var(mc_buffer);
-
         return ret;
 }