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| author | Akinobu Mita <akinobu.mita@gmail.com> | 2015-09-26 19:09:23 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-09-29 19:32:50 +0200 |
| commit | 5778322e67ed34dc9f391a4a5cbcbb856071ceba (patch) | |
| tree | 142b9e7ac2a85dc3ee7cfd403f53b56cb2921957 /block/blk-mq.h | |
| parent | blk-mq: fix q->mq_usage_counter access race (diff) | |
| download | linux-5778322e67ed34dc9f391a4a5cbcbb856071ceba.tar.xz linux-5778322e67ed34dc9f391a4a5cbcbb856071ceba.zip | |
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 <akinobu.mita@gmail.com>
Reviewed-by: Ming Lei <tom.leiming@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ming Lei <tom.leiming@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq.h')
| -rw-r--r-- | block/blk-mq.h | 3 |
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); /* |