linux-kernel - Re: [PATCH] NVMe: do not touch sq door bell if nvmeq has been suspended

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Message-ID: <20160208150132.GA25111@localhost.localdomain>
Date:	Mon, 8 Feb 2016 15:01:33 +0000
From:	Keith Busch <keith.busch@...el.com>
To:	Wenbo Wang <wenbo.wang@...blaze.com>
Cc:	Jens Axboe <axboe@...com>, Wenbo Wang <mail_weber_wang@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
	"Wenwei.Tao" <wenwei.tao@...blaze.com>
Subject: Re: [PATCH] NVMe: do not touch sq door bell if nvmeq has been
 suspended

On Sat, Feb 06, 2016 at 02:32:24PM +0000, Wenbo Wang wrote:
> Keith,
> 
> Is the following solution OK?
> synchronize_rcu guarantee that no queue_rq is running concurrently with device disable code. Together with your another patch (adding blk_sync_queue), both sync/async path shall be handled correctly.
> 
> Do you think synchronize_rcu shall be added to blk_sync_queue?

I was nearly going to suggest the same last week, but it feels wrong since
no one takes rcu_read_lock in the path we're trying to sychronoize. Is
this safe if the task is interrupted?