From: Bart Van Assche <bvanassche@acm.org>
To: Christoph Hellwig <hch@lst.de>
Cc: linux-block@vger.kernel.org, John Garry <john.garry@huawei.com>,
Hannes Reinecke <hare@suse.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ming Lei <ming.lei@redhat.com>
Subject: Re: [PATCH 8/8] blk-mq: drain I/O when all CPUs in a hctx are offline
Date: Wed, 27 May 2020 16:09:19 -0700 [thread overview]
Message-ID: <7acc7ab5-02f9-e6ee-e95f-175bc0df9cbc@acm.org> (raw)
In-Reply-To: <20200527180644.514302-9-hch@lst.de>
On 2020-05-27 11:06, Christoph Hellwig wrote:
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -180,6 +180,14 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
> sbitmap_finish_wait(bt, ws, &wait);
>
> found_tag:
> + /*
> + * Give up this allocation if the hctx is inactive. The caller will
> + * retry on an active hctx.
> + */
> + if (unlikely(test_bit(BLK_MQ_S_INACTIVE, &data->hctx->state))) {
> + blk_mq_put_tag(tags, data->ctx, tag + tag_offset);
> + return -1;
> + }
> return tag + tag_offset;
> }
The code that has been added in blk_mq_hctx_notify_offline() will only
work correctly if blk_mq_get_tag() tests BLK_MQ_S_INACTIVE after the
store instructions involved in the tag allocation happened. Does this
mean that a memory barrier should be added in the above function before
the test_bit() call?
Thanks,
Bart.
next prev parent reply other threads:[~2020-05-27 23:09 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-27 18:06 blk-mq: improvement CPU hotplug (simplified version) v4 Christoph Hellwig
2020-05-27 18:06 ` [PATCH 1/8] blk-mq: remove the bio argument to ->prepare_request Christoph Hellwig
2020-05-27 18:16 ` Johannes Thumshirn
2020-05-27 18:06 ` [PATCH 2/8] blk-mq: simplify the blk_mq_get_request calling convention Christoph Hellwig
2020-05-27 18:17 ` Johannes Thumshirn
2020-05-27 18:06 ` [PATCH 3/8] blk-mq: move more request initialization to blk_mq_rq_ctx_init Christoph Hellwig
2020-05-27 18:16 ` Hannes Reinecke
2020-05-28 9:50 ` Johannes Thumshirn
2020-05-27 18:06 ` [PATCH 4/8] blk-mq: rename BLK_MQ_TAG_FAIL to BLK_MQ_NO_TAG Christoph Hellwig
2020-05-27 18:14 ` Johannes Thumshirn
2020-05-27 18:17 ` Hannes Reinecke
2020-05-27 22:38 ` Bart Van Assche
2020-05-27 18:06 ` [PATCH 5/8] blk-mq: use BLK_MQ_NO_TAG in more places Christoph Hellwig
2020-05-27 18:15 ` Johannes Thumshirn
2020-05-27 18:18 ` Hannes Reinecke
2020-05-27 22:38 ` Bart Van Assche
2020-05-27 18:06 ` [PATCH 6/8] blk-mq: open code __blk_mq_alloc_request in blk_mq_alloc_request_hctx Christoph Hellwig
2020-05-27 18:06 ` [PATCH 7/8] blk-mq: add blk_mq_all_tag_iter Christoph Hellwig
2020-05-27 18:21 ` Hannes Reinecke
2020-05-27 22:52 ` Bart Van Assche
2020-05-27 18:06 ` [PATCH 8/8] blk-mq: drain I/O when all CPUs in a hctx are offline Christoph Hellwig
2020-05-27 18:26 ` Hannes Reinecke
2020-05-27 23:09 ` Bart Van Assche [this message]
2020-05-28 1:46 ` Ming Lei
2020-05-28 3:33 ` Bart Van Assche
2020-05-28 5:19 ` Ming Lei
2020-05-28 13:37 ` Bart Van Assche
2020-05-28 17:21 ` Paul E. McKenney
2020-05-29 1:53 ` Ming Lei
2020-05-29 3:07 ` Paul E. McKenney
2020-05-29 3:53 ` Ming Lei
2020-05-29 18:13 ` Paul E. McKenney
2020-05-29 19:55 ` Bart Van Assche
2020-05-29 21:12 ` Paul E. McKenney
2020-05-29 1:13 ` Ming Lei
2020-05-27 20:07 ` blk-mq: improvement CPU hotplug (simplified version) v4 Bart Van Assche
2020-05-27 20:31 ` John Garry
2020-05-29 13:26 ` Christoph Hellwig
2020-05-28 8:29 ` John Garry
-- strict thread matches above, loose matches on Subject: below --
2020-05-29 13:53 Christoph Hellwig
2020-05-29 13:53 ` [PATCH 8/8] blk-mq: drain I/O when all CPUs in a hctx are offline Christoph Hellwig
2020-05-29 14:34 ` Hannes Reinecke
2020-05-29 14:41 ` Daniel Wagner
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