This is a note to let you know that I've just added the patch titled
blk-mq: fix potential hang if rolling wakeup depth is too high
to the 3.17-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
blk-mq-fix-potential-hang-if-rolling-wakeup-depth-is-too-high.patch
and it can be found in the queue-3.17 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From abab13b5c4fd1fec4f9a61622548012d93dc2831 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@xxxxxx>
Date: Tue, 7 Oct 2014 08:39:20 -0600
Subject: blk-mq: fix potential hang if rolling wakeup depth is too high
From: Jens Axboe <axboe@xxxxxx>
commit abab13b5c4fd1fec4f9a61622548012d93dc2831 upstream.
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@xxxxxxx>
Fixes: 4bb659b156996
Signed-off-by: Jens Axboe <axboe@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
block/blk-mq-tag.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -463,8 +463,8 @@ static void bt_update_count(struct blk_m
}
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;
}
Patches currently in stable-queue which might be from axboe@xxxxxx are
queue-3.17/blk-mq-fix-potential-hang-if-rolling-wakeup-depth-is-too-high.patch
queue-3.17/block-fix-alignment_offset-math-that-assumes-io_min-is-a-power-of-2.patch
queue-3.17/drbd-compute-the-end-before-rb_insert_augmented.patch
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