Some request_fn implementations, e.g. scsi_request_fn(), unlock
the queue lock internally. This may result in multiple threads
executing request_fn for the same queue simultaneously. Keep
track of the number of active request_fn calls and make sure that
blk_cleanup_queue() waits until all active request_fn invocations
have finished. A block driver may start cleaning up resources
needed by its request_fn as soon as blk_cleanup_queue() finished,
so blk_cleanup_queue() must wait for all outstanding request_fn
invocations to finish.
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
Reported-by: Chanho Min <chanho.min@xxxxxxx>
Cc: James Bottomley <JBottomley@xxxxxxxxxxxxx>
Cc: Mike Christie <michaelc@xxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
---
block/blk-core.c | 10 ++++++++++
include/linux/blkdev.h | 6 ++++++
2 files changed, 16 insertions(+)
diff --git a/block/blk-core.c b/block/blk-core.c
index 12deca9..4d09af4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -309,7 +309,16 @@ inline void __blk_run_queue_uncond(struct request_queue *q)
if (unlikely(blk_queue_dead(q)))
return;
+ /*
+ * Some request_fn implementations, e.g. scsi_request_fn(), unlock
+ * the queue lock internally. As a result multiple threads may be
+ * running such a request function concurrently. Keep track of the
+ * number of active request_fn invocations such that blk_drain_queue()
+ * can wait until all these request_fn calls have finished.
+ */
+ q->request_fn_active++;
q->request_fn(q);
+ q->request_fn_active--;
}
/**
@@ -408,6 +417,7 @@ static void __blk_drain_queue(struct request_queue *q, bool drain_all)
__blk_run_queue(q);
drain |= q->nr_rqs_elvpriv;
+ drain |= q->request_fn_active;
/*
* Unfortunately, requests are queued at and tracked from
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8bc46c2..c9d233e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -378,6 +378,12 @@ struct request_queue {
unsigned int nr_sorted;
unsigned int in_flight[2];
+ /*
+ * Number of active block driver functions for which blk_drain_queue()
+ * must wait. Must be incremented around functions that unlock the
+ * queue_lock internally, e.g. scsi_request_fn().
+ */
+ unsigned int request_fn_active;
unsigned int rq_timeout;
struct timer_list timeout;
--
1.7.10.4
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