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authorBart Van Assche <bart.vanassche@wdc.com>2018-03-19 11:46:13 -0700
committerJens Axboe <axboe@kernel.dk>2018-03-19 12:50:10 -0600
commit818e0fa293ca836eba515615c64680ea916fd7cd (patch)
treee3f01a690b1d58a1e316b9f7588c04a43a9a972c
parent5f2b18ec8e1643410a2369f06888951cdedea0bf (diff)
downloadlinux-818e0fa293ca836eba515615c64680ea916fd7cd.tar.bz2
block: Change a rcu_read_{lock,unlock}_sched() pair into rcu_read_{lock,unlock}()
scsi_device_quiesce() uses synchronize_rcu() to guarantee that the effect of blk_set_preempt_only() will be visible for percpu_ref_tryget() calls that occur after the queue unfreeze by using the approach explained in https://lwn.net/Articles/573497/. The rcu read lock and unlock calls in blk_queue_enter() form a pair with the synchronize_rcu() call in scsi_device_quiesce(). Both scsi_device_quiesce() and blk_queue_enter() must either use regular RCU or RCU-sched. Since neither the RCU-protected code in blk_queue_enter() nor blk_queue_usage_counter_release() sleeps, regular RCU protection is sufficient. Note: scsi_device_quiesce() does not have to be modified since it already uses synchronize_rcu(). Reported-by: Tejun Heo <tj@kernel.org> Fixes: 3a0a529971ec ("block, scsi: Make SCSI quiesce and resume work reliably") Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com> Acked-by: Tejun Heo <tj@kernel.org> Cc: Tejun Heo <tj@kernel.org> Cc: Hannes Reinecke <hare@suse.com> Cc: Ming Lei <ming.lei@redhat.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Johannes Thumshirn <jthumshirn@suse.de> Cc: Oleksandr Natalenko <oleksandr@natalenko.name> Cc: Martin Steigerwald <martin@lichtvoll.de> Cc: stable@vger.kernel.org # v4.15 Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/blk-core.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 5e88c579e896..a0f675f84f86 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -917,7 +917,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
bool success = false;
int ret;
- rcu_read_lock_sched();
+ rcu_read_lock();
if (percpu_ref_tryget_live(&q->q_usage_counter)) {
/*
* The code that sets the PREEMPT_ONLY flag is
@@ -930,7 +930,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags)
percpu_ref_put(&q->q_usage_counter);
}
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();
if (success)
return 0;