On 2019-11-15 23:17, Ming Lei wrote:
> Now blk-mq takes a static queue mapping between CPU and hw queues, given
> CPU hotplug may happen any time, so the specified hw queue may become
> inactive any time.
Hi Ming,
I can trigger a race between blk_mq_alloc_request_hctx() and
CPU-hotplugging by running blktests. The patch below fixes that race
on my setup. Does this patch also fix the race(s) that you ran into?
Thanks,
Bart.
Subject: [PATCH] blk-mq: Fix a race between blk_mq_alloc_request_hctx() and
CPU hot-plugging
---
block/blk-mq.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 20a71dcdc339..16057aa2307f 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -442,13 +442,15 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
if (WARN_ON_ONCE(!(flags & BLK_MQ_REQ_NOWAIT)))
return ERR_PTR(-EINVAL);
- if (hctx_idx >= q->nr_hw_queues)
- return ERR_PTR(-EIO);
-
ret = blk_queue_enter(q, flags);
if (ret)
return ERR_PTR(ret);
+ if (hctx_idx >= q->nr_hw_queues) {
+ blk_queue_exit(q);
+ return ERR_PTR(-EIO);
+ }
+
/*
* Check if the hardware context is actually mapped to anything.
* If not tell the caller that it should skip this queue.
