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

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Message-ID: <20160209225548.GA32064@localhost.localdomain>
Date:	Tue, 9 Feb 2016 22:55:49 +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 Tue, Feb 09, 2016 at 11:22:04AM +0000, Wenbo Wang wrote:
> In most cases, rcu read lock is just a preempt_disable, which is what get_cpu does. I don't see any risk.

Yes, many rcu_read_lock cases expand similarly to get_cpu. What about
the other cases?

FWIW, I don't think we'll hit the problem with the proposed rcu sync.
Heck, we don't even have a synchronize today and we don't hit the
theoretical problem.