On 09/13/12 18:53, Tejun Heo wrote:
> Oh yeah, I definitely think this is something which needs to be solved
> from the block layer but I'm hoping this could cover the case Chanho
> is trying to solve too. They're different but similar problems - you
> don't want blk_cleanup_queue() to finish while someone is executing
> inside it and you don't want anyone to enter it after
> blk_cleanup_queue() is finished, so I really think we should have
> block layer solution which fixes both problems. That should be
> possible, right?
If I do not receive further feedback I'll start testing the patch below
(on top of the patch at the start of this thread):
[PATCH] Avoid that request_fn() gets invoked after draining the queue finished
---
block/blk-core.c | 4 ++++
include/linux/blkdev.h | 2 ++
2 files changed, 6 insertions(+), 0 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index a668b71..575b7c4 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -305,6 +305,9 @@ EXPORT_SYMBOL(blk_sync_queue);
*/
void __blk_run_queue_uncond(struct request_queue *q)
{
+ if (unlikely(blk_queue_drained(q)))
+ return;
+
q->request_fn_active++;
q->request_fn(q);
q->request_fn_active--;
@@ -532,6 +535,7 @@ void blk_cleanup_queue(struct request_queue *q)
blk_sync_queue(q);
spin_lock_irq(lock);
+ queue_flag_set(QUEUE_FLAG_DRAINED, q);
if (q->queue_lock != &q->__queue_lock)
q->queue_lock = &q->__queue_lock;
spin_unlock_irq(lock);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 132334e..ceebc39 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -456,6 +456,7 @@ struct request_queue {
#define QUEUE_FLAG_ADD_RANDOM 16 /* Contributes to random pool */
#define QUEUE_FLAG_SECDISCARD 17 /* supports SECDISCARD */
#define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */
+#define QUEUE_FLAG_DRAINED 19 /* queue tear-down finished */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -526,6 +527,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_tagged(q) test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)
#define blk_queue_stopped(q) test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)
#define blk_queue_dead(q) test_bit(QUEUE_FLAG_DEAD, &(q)->queue_flags)
+#define blk_queue_drained(q) test_bit(QUEUE_FLAG_DRAINED, &(q)->queue_flags)
#define blk_queue_bypass(q) test_bit(QUEUE_FLAG_BYPASS, &(q)->queue_flags)
#define blk_queue_nomerges(q) test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)
#define blk_queue_noxmerges(q) \
--
1.7.7
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