Linux 6.9-rc6

[sfrench/cifs-2.6.git] / kernel / sched / sched.h

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d2242679239ec5ad49152400350882d7d7b9819c..ae50f212775e5c529be68b440d16258c9f2d1d10 100644 (file)
--- 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);