From: Keith Busch <kbusch@kernel.org>
To: Alexey Dobriyan <adobriyan@gmail.com>
Cc: axboe@fb.com, John Garry <john.garry@huawei.com>,
hch@lst.de, linux-nvme@lists.infradead.org, sagi@grimberg.me
Subject: Re: [PATCH] nvme-pci: slimmer CQ head update
Date: Wed, 6 May 2020 08:44:34 -0600 [thread overview]
Message-ID: <20200506144434.GB54933@C02WT3WMHTD6> (raw)
In-Reply-To: <20200506132429.GA21451@avx2>
On Wed, May 06, 2020 at 04:24:29PM +0300, Alexey Dobriyan wrote:
> static inline void nvme_update_cq_head(struct nvme_queue *nvmeq)
> {
> - if (++nvmeq->cq_head == nvmeq->q_depth) {
> + /*
> + * Can't pre-increment ->cq_head directly.
> + * It must be in [0, ->q_depth) range at all times.
> + */
> + u16 tmp = READ_ONCE(nvmeq->cq_head);
> + if (++tmp == nvmeq->q_depth) {
This looks correct too, but there's no need for the READ_ONCE access,
or the pre-increment:
u16 tmp = nvmeq->cq_head + 1;
if (tmp == nvmeq->q_depth) {
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next prev parent reply other threads:[~2020-05-06 14:44 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-28 18:45 [PATCH] nvme-pci: slimmer CQ head update Alexey Dobriyan
2020-02-29 5:53 ` Keith Busch
2020-05-06 11:03 ` John Garry
2020-05-06 12:47 ` Keith Busch
2020-05-06 13:24 ` Alexey Dobriyan
2020-05-06 13:44 ` John Garry
2020-05-06 14:01 ` Alexey Dobriyan
2020-05-06 14:35 ` Christoph Hellwig
2020-05-06 16:26 ` John Garry
2020-05-06 16:31 ` Will Deacon
2020-05-06 16:52 ` Robin Murphy
2020-05-06 17:02 ` John Garry
2020-05-07 8:18 ` John Garry
2020-05-07 11:04 ` Robin Murphy
2020-05-07 13:55 ` John Garry
2020-05-07 14:23 ` Keith Busch
2020-05-07 15:11 ` John Garry
2020-05-07 15:35 ` Keith Busch
2020-05-07 15:41 ` John Garry
2020-05-08 16:16 ` Keith Busch
2020-05-08 17:04 ` John Garry
2020-05-07 16:26 ` Robin Murphy
2020-05-07 17:35 ` Keith Busch
2020-05-07 17:44 ` Will Deacon
2020-05-07 18:06 ` Keith Busch
2020-05-08 11:40 ` Will Deacon
2020-05-08 14:07 ` Keith Busch
2020-05-08 15:34 ` Keith Busch
2020-05-06 14:44 ` Keith Busch [this message]
2020-05-07 15:58 ` Keith Busch
2020-05-07 20:07 ` [PATCH] nvme-pci: fix "slimmer CQ head update" Alexey Dobriyan
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