diff options
| author | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-05-13 15:57:50 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@linux.ibm.com> | 2019-08-13 14:35:49 -0700 |
| commit | e6060b41c9955374079926a7612b857a8458ed1f (patch) | |
| tree | 297581f29d4caec633aa474b3b4dc30f16e5cffe /kernel/rcu | |
| parent | 76c6927c3ee443e756f2c0c9f992cb04b26c65f2 (diff) | |
rcu/nocb: Allow lockless use of rcu_segcblist_empty()
Currently, rcu_segcblist_empty() assumes that the callback list is not
being changed by other CPUs, but upcoming changes will require it to
operate locklessly. This commit therefore adds the needed READ_ONCE()
call, along with the WRITE_ONCE() calls when updating the callback list's
->head field.
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/rcu_segcblist.c | 4 | ||||
| -rw-r--r-- | kernel/rcu/rcu_segcblist.h | 2 |
2 files changed, 3 insertions, 3 deletions
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c index 0e7fe678b6ac..06435a368be5 100644 --- a/kernel/rcu/rcu_segcblist.c +++ b/kernel/rcu/rcu_segcblist.c @@ -213,7 +213,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp, if (!rcu_segcblist_ready_cbs(rsclp)) return; /* Nothing to do. */ *rclp->tail = rsclp->head; - rsclp->head = *rsclp->tails[RCU_DONE_TAIL]; + WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]); WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL); rclp->tail = rsclp->tails[RCU_DONE_TAIL]; for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--) @@ -268,7 +268,7 @@ void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp, if (!rclp->head) return; /* No callbacks to move. */ *rclp->tail = rsclp->head; - rsclp->head = rclp->head; + WRITE_ONCE(rsclp->head, rclp->head); for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) if (&rsclp->head == rsclp->tails[i]) WRITE_ONCE(rsclp->tails[i], rclp->tail); diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h index f74960f0305c..d9142b3590a8 100644 --- a/kernel/rcu/rcu_segcblist.h +++ b/kernel/rcu/rcu_segcblist.h @@ -36,7 +36,7 @@ struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp); */ static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp) { - return !rsclp->head; + return !READ_ONCE(rsclp->head); } /* Return number of callbacks in segmented callback list. */ |