From mboxrd@z Thu Jan  1 00:00:00 1970
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Subject: Re: [PATCH 06/16] mmc: core: replace waitqueue with worker
To: Adrian Hunter <adrian.hunter@intel.com>,
 Linus Walleij <linus.walleij@linaro.org>
References: <20170209153403.9730-1-linus.walleij@linaro.org>
 <20170209153403.9730-7-linus.walleij@linaro.org>
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 <CACRpkdYOyEs8vxmPt1kGiKJrw8+16DyD8Nn=ke6mgxPaCQynCw@mail.gmail.com>
 <3fc89f9f-fbcf-113d-3644-b6c9dae003f0@intel.com>
Cc: "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
 Ulf Hansson <ulf.hansson@linaro.org>,
 Paolo Valente <paolo.valente@linaro.org>,
 Chunyan Zhang <zhang.chunyan@linaro.org>,
 Baolin Wang <baolin.wang@linaro.org>, linux-block@vger.kernel.org,
 Christoph Hellwig <hch@lst.de>, Arnd Bergmann <arnd@arndb.de>
From: Jens Axboe <axboe@kernel.dk>
Message-ID: <8f1f3d4c-410c-2632-c776-4ced363bdb0d@kernel.dk>
Date: Fri, 10 Mar 2017 15:05:13 -0700
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On 03/10/2017 07:21 AM, Adrian Hunter wrote:
>> Essentially I take out that thread and replace it with this one worker
>> introduced in this very patch. I agree the driver can block in many ways
>> and that is why I need to have it running in process context, and this
>> is what the worker introduced here provides.
> 
> The last time I looked at the blk-mq I/O scheduler code, it pulled up to
> qdepth requests from the I/O scheduler and left them on a local list while
> running ->queue_rq().  That means blocking in ->queue_rq() leaves some
> number of requests in limbo (not issued but also not in the I/O scheduler)
> for that time.

Look again, if we're not handling the requeued dispatches, we pull one
at the time from the scheduler.

-- 
Jens Axboe