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author | Shaohua Li <shli@fb.com> | 2015-05-04 14:32:48 -0600 |
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committer | Jens Axboe <axboe@fb.com> | 2015-05-04 14:32:48 -0600 |
commit | 9ba52e5812e53f20f23600d79449a3ec05a0254f (patch) | |
tree | fbcac9cb92b6540370ee63bb4db3b466302fede3 | |
parent | b2387ddcced8de3e6471a2fb16a409577063016f (diff) | |
download | linux-exynos-9ba52e5812e53f20f23600d79449a3ec05a0254f.tar.gz linux-exynos-9ba52e5812e53f20f23600d79449a3ec05a0254f.tar.bz2 linux-exynos-9ba52e5812e53f20f23600d79449a3ec05a0254f.zip |
blk-mq: don't lose requests if a stopped queue restarts
Normally if driver is busy to dispatch a request the logic is like below:
block layer: driver:
__blk_mq_run_hw_queue
a. blk_mq_stop_hw_queue
b. rq add to ctx->dispatch
later:
1. blk_mq_start_hw_queue
2. __blk_mq_run_hw_queue
But it's possible step 1-2 runs between a and b. And since rq isn't in
ctx->dispatch yet, step 2 will not run rq. The rq might get lost if
there are no subsequent requests kick in.
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
-rw-r--r-- | block/blk-mq.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 76f460e36f1d..e68b71b85a7e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -858,6 +858,16 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) spin_lock(&hctx->lock); list_splice(&rq_list, &hctx->dispatch); spin_unlock(&hctx->lock); + /* + * the queue is expected stopped with BLK_MQ_RQ_QUEUE_BUSY, but + * it's possible the queue is stopped and restarted again + * before this. Queue restart will dispatch requests. And since + * requests in rq_list aren't added into hctx->dispatch yet, + * the requests in rq_list might get lost. + * + * blk_mq_run_hw_queue() already checks the STOPPED bit + **/ + blk_mq_run_hw_queue(hctx, true); } } |