From: Jens Axboe <axboe@kernel.dk>
To: "jianchao.wang" <jianchao.w.wang@oracle.com>,
linux-block@vger.kernel.org
Subject: Re: [PATCH 05/11] block: avoid ordered task state change for polled IO
Date: Tue, 13 Nov 2018 19:35:40 -0700 [thread overview]
Message-ID: <7d16853c-dbeb-45bb-3902-faa5aefad9bb@kernel.dk> (raw)
In-Reply-To: <cc187e6f-dd59-8986-057a-99fbc247efd5@oracle.com>
On 11/13/18 7:29 PM, jianchao.wang wrote:
> Hi Jens
>
> On 11/13/18 11:42 PM, Jens Axboe wrote:
>> @@ -181,6 +181,7 @@ static void blkdev_bio_end_io_simple(struct bio *bio)
>> struct task_struct *waiter = bio->bi_private;
>>
>> WRITE_ONCE(bio->bi_private, NULL);
>> + smp_wmb();
>> wake_up_process(waiter);
>> }
>
>
> The wake up path has contained a full memory barrier with the raw_spin_lock
> and following smp_mb__after_spinlock
>
> Please refer to:
>
> wake_up_process
> -> try_to_wake_up
>
> raw_spin_lock_irqsave(&p->pi_lock, flags);
> smp_mb__after_spinlock();
>
> So the smp_wmb here is not necessary.
And I guess we don't need it for the next patch either, since the path
that doesn't take wake_up_process() is local.
I'll update them (again), thanks!
--
Jens Axboe
next prev parent reply other threads:[~2018-11-14 2:35 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-13 15:42 [PATCHSET v2 0/11] Various block optimizations Jens Axboe
2018-11-13 15:42 ` [PATCH 01/11] nvme: don't disable local ints for polled queue Jens Axboe
2018-11-13 15:42 ` Jens Axboe
2018-11-13 15:42 ` [PATCH 02/11] block: add queue_is_mq() helper Jens Axboe
2018-11-14 15:23 ` Christoph Hellwig
2018-11-13 15:42 ` [PATCH 03/11] blk-mq: embed blk_mq_ops directly in the request queue Jens Axboe
2018-11-13 15:42 ` [PATCH 04/11] blk-rq-qos: inline check for q->rq_qos functions Jens Axboe
2018-11-13 15:42 ` [PATCH 05/11] block: avoid ordered task state change for polled IO Jens Axboe
2018-11-14 2:29 ` jianchao.wang
2018-11-14 2:35 ` Jens Axboe [this message]
2018-11-13 15:42 ` [PATCH 06/11] block: add polled wakeup task helper Jens Axboe
2018-11-13 15:52 ` Keith Busch
2018-11-13 15:58 ` Jens Axboe
2018-11-13 16:59 ` Jens Axboe
2018-11-13 15:42 ` [PATCH 07/11] block: have ->poll_fn() return number of entries polled Jens Axboe
2018-11-13 15:42 ` [PATCH 08/11] blk-mq: when polling for IO, look for any completion Jens Axboe
2018-11-13 15:42 ` [PATCH 09/11] block: make blk_poll() take a parameter on whether to spin or not Jens Axboe
2018-11-13 15:42 ` [PATCH 10/11] block: for async O_DIRECT, mark us as polling if asked to Jens Axboe
2018-11-13 15:42 ` [PATCH 11/11] block: don't plug for aio/O_DIRECT HIPRI IO Jens Axboe
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