diff options
| -rw-r--r-- | include/net/sch_generic.h | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h index 1e625519ae96..57710303908c 100644 --- a/include/net/sch_generic.h +++ b/include/net/sch_generic.h @@ -163,6 +163,12 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc) if (spin_trylock(&qdisc->seqlock)) goto nolock_empty; + /* Paired with smp_mb__after_atomic() to make sure + * STATE_MISSED checking is synchronized with clearing + * in pfifo_fast_dequeue(). + */ + smp_mb__before_atomic(); + /* If the MISSED flag is set, it means other thread has * set the MISSED flag before second spin_trylock(), so * we can return false here to avoid multi cpus doing @@ -180,6 +186,12 @@ static inline bool qdisc_run_begin(struct Qdisc *qdisc) */ set_bit(__QDISC_STATE_MISSED, &qdisc->state); + /* spin_trylock() only has load-acquire semantic, so use + * smp_mb__after_atomic() to ensure STATE_MISSED is set + * before doing the second spin_trylock(). + */ + smp_mb__after_atomic(); + /* Retry again in case other CPU may not see the new flag * after it releases the lock at the end of qdisc_run_end(). */ |