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| author | Jens Axboe <axboe@fb.com> | 2014-10-07 08:39:20 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2014-10-07 08:39:20 -0600 |
| commit | abab13b5c4fd1fec4f9a61622548012d93dc2831 (patch) | |
| tree | e73fa24015b0a494fbe9dab8a1e9b3460c935b87 /block | |
| parent | d8f429e1669b9709f5b669aac9d734dbe0640891 (diff) | |
| download | lwn-abab13b5c4fd1fec4f9a61622548012d93dc2831.tar.gz lwn-abab13b5c4fd1fec4f9a61622548012d93dc2831.zip | |
blk-mq: fix potential hang if rolling wakeup depth is too high
We currently divide the queue depth by 4 as our batch wakeup
count, but we split the wakeups over BT_WAIT_QUEUES number of
wait queues. This defaults to 8. If the product of the resulting
batch wake count and BT_WAIT_QUEUES is higher than the device
queue depth, we can get into a situation where a task goes to
sleep waiting for a request, but never gets woken up.
Reported-by: Bart Van Assche <bvanassche@acm.org>
Fixes: 4bb659b156996
Cc: stable@kernel.org
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq-tag.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index b08788086414..146fd02659ec 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -455,8 +455,8 @@ static void bt_update_count(struct blk_mq_bitmap_tags *bt, } bt->wake_cnt = BT_WAIT_BATCH; - if (bt->wake_cnt > depth / 4) - bt->wake_cnt = max(1U, depth / 4); + if (bt->wake_cnt > depth / BT_WAIT_QUEUES) + bt->wake_cnt = max(1U, depth / BT_WAIT_QUEUES); bt->depth = depth; } |