path: root/block/blk-mq.h
diff options
authorAkinobu Mita <>2015-09-27 02:09:23 +0900
committerJens Axboe <>2015-09-29 11:32:50 -0600
commit5778322e67ed34dc9f391a4a5cbcbb856071ceba (patch)
tree142b9e7ac2a85dc3ee7cfd403f53b56cb2921957 /block/blk-mq.h
parent0e6263682014d480b8d7b8c10287f4536066b54f (diff)
blk-mq: avoid inserting requests before establishing new mapping
Notifier callbacks for CPU_ONLINE action can be run on the other CPU than the CPU which was just onlined. So it is possible for the process running on the just onlined CPU to insert request and run hw queue before establishing new mapping which is done by blk_mq_queue_reinit_notify(). This can cause a problem when the CPU has just been onlined first time since the request queue was initialized. At this time ctx->index_hw for the CPU, which is the index in hctx->ctxs[] for this ctx, is still zero before blk_mq_queue_reinit_notify() is called by notifier callbacks for CPU_ONLINE action. For example, there is a single hw queue (hctx) and two CPU queues (ctx0 for CPU0, and ctx1 for CPU1). Now CPU1 is just onlined and a request is inserted into ctx1->rq_list and set bit0 in pending bitmap as ctx1->index_hw is still zero. And then while running hw queue, flush_busy_ctxs() finds bit0 is set in pending bitmap and tries to retrieve requests in hctx->ctxs[0]->rq_list. But htx->ctxs[0] is a pointer to ctx0, so the request in ctx1->rq_list is ignored. Fix it by ensuring that new mapping is established before onlined cpu starts running. Signed-off-by: Akinobu Mita <> Reviewed-by: Ming Lei <> Cc: Jens Axboe <> Cc: Ming Lei <> Reviewed-by: Christoph Hellwig <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/blk-mq.h')
1 files changed, 2 insertions, 1 deletions
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 6a48c4c0d8a2..f4fea7964910 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -51,7 +51,8 @@ void blk_mq_disable_hotplug(void);
* CPU -> queue mappings
extern unsigned int *blk_mq_make_queue_map(struct blk_mq_tag_set *set);
-extern int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues);
+extern int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues,
+ const struct cpumask *online_mask);
extern int blk_mq_hw_queue_to_node(unsigned int *map, unsigned int);