mtrr atomicity fix

Rafael gets this on an SMP box with kernel preemption enabled, during
hibernation and restore (100% of the time):

Enabling non-boot CPUs ...
BUG: using smp_processor_id() in preemptible [00000001] code: bash/4514
caller is mtrr_save_state+0x9/0x40

Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/arch/i386/kernel/cpu/mtrr/main.c b/arch/i386/kernel/cpu/mtrr/main.c
index 1cf466df330a..7202b98aac4f 100644
--- a/arch/i386/kernel/cpu/mtrr/main.c
+++ b/arch/i386/kernel/cpu/mtrr/main.c
@@ -734,10 +734,13 @@ void mtrr_ap_init(void)
  */
 void mtrr_save_state(void)
 {
-        if (smp_processor_id() == 0)
+        int cpu = get_cpu();
+
+        if (cpu == 0)
                 mtrr_save_fixed_ranges(NULL);
         else
                 smp_call_function_single(0, mtrr_save_fixed_ranges, NULL, 1, 1);
+        put_cpu();
 }
 
 static int __init mtrr_init_finialize(void)