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-rw-r--r--kernel/sched/sched.h20
1 files changed, 14 insertions, 6 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d2242679239e..ae50f212775e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -79,6 +79,8 @@
# include <asm/paravirt_api_clock.h>
#endif
+#include <asm/barrier.h>
+
#include "cpupri.h"
#include "cpudeadline.h"
@@ -3445,13 +3447,19 @@ static inline void switch_mm_cid(struct rq *rq,
* between rq->curr store and load of {prev,next}->mm->pcpu_cid[cpu].
* Provide it here.
*/
- if (!prev->mm) // from kernel
+ if (!prev->mm) { // from kernel
smp_mb();
- /*
- * user -> user transition guarantees a memory barrier through
- * switch_mm() when current->mm changes. If current->mm is
- * unchanged, no barrier is needed.
- */
+ } else { // from user
+ /*
+ * user->user transition relies on an implicit
+ * memory barrier in switch_mm() when
+ * current->mm changes. If the architecture
+ * switch_mm() does not have an implicit memory
+ * barrier, it is emitted here. If current->mm
+ * is unchanged, no barrier is needed.
+ */
+ smp_mb__after_switch_mm();
+ }
}
if (prev->mm_cid_active) {
mm_cid_snapshot_time(rq, prev->mm);