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Date:   Fri, 24 Apr 2020 12:38:51 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Ming Lei <ming.lei@redhat.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        John Garry <john.garry@huawei.com>,
        Bart Van Assche <bvanassche@acm.org>,
        Hannes Reinecke <hare@suse.com>,
        Christoph Hellwig <hch@lst.de>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH V8 07/11] blk-mq: stop to handle IO and drain IO before
 hctx becomes inactive
Message-ID: <20200424103851.GD28156@lst.de>
References: <20200424102351.475641-1-ming.lei@redhat.com> <20200424102351.475641-8-ming.lei@redhat.com>
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On Fri, Apr 24, 2020 at 06:23:47PM +0800, Ming Lei wrote:
> Before one CPU becomes offline, check if it is the last online CPU of hctx.
> If yes, mark this hctx as inactive, meantime wait for completion of all
> in-flight IOs originated from this hctx. Meantime check if this hctx has
> become inactive in blk_mq_get_driver_tag(), if yes, release the
> allocated tag.
> 
> This way guarantees that there isn't any inflight IO before shutdowning
> the managed IRQ line when all CPUs of this IRQ line is offline.

Can you take a look at all my comments on the previous version here
(splitting blk_mq_get_driver_tag for direct_issue vs not, what is
the point of barrier(), smp_mb__before_atomic and
smp_mb__after_atomic), as none seems to be addressed and I also didn't
see a reply.