powerpc: Add write barrier before enabling DTL flags

Currently, we don't enforce any ordering for updates to the lppaca
when enabling dtl logging, so we may end up enabling logging before the
index fields have been established.

This change adds a smp_wmb() before doing the actual enable.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

diff --git a/arch/powerpc/platforms/pseries/dtl.c b/arch/powerpc/platforms/pseries/dtl.c
index dc9b0f81e60f9420e0129cfa5bf68ca1c6185a41..fafcaa0e81ef593c6ed346493ed76926f21120c5 100644 (file)
--- a/arch/powerpc/platforms/pseries/dtl.c
+++ b/arch/powerpc/platforms/pseries/dtl.c
@@ -107,6 +107,10 @@ static int dtl_enable(struct dtl *dtl)
        /* set our initial buffer indices */
        dtl->last_idx = lppaca[dtl->cpu].dtl_idx = 0;
 
+       /* ensure that our updates to the lppaca fields have occurred before
+        * we actually enable the logging */
+       smp_wmb();
+
        /* enable event logging */
        lppaca[dtl->cpu].dtl_enable_mask = dtl_event_mask;