From: Jia-Ju Bai <baijiaju1990@gmail.com>
To: James Bottomley <James.Bottomley@HansenPartnership.com>,
davem@davemloft.net, stephen@networkplumber.org,
johannes.berg@intel.com, arvind.yadav.cs@gmail.com,
dhowells@redhat.com
Cc: netdev@vger.kernel.org, linux-parisc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] dec: tulip: de4x5: Replace mdelay with usleep_range in de4x5_hw_init
Date: Thu, 12 Apr 2018 09:30:32 +0800 [thread overview]
Message-ID: <8bac3385-97c6-fff1-17c6-11f5e98a039a@gmail.com> (raw)
In-Reply-To: <1523463379.3221.18.camel@HansenPartnership.com>
On 2018/4/12 0:16, James Bottomley wrote:
> On Wed, 2018-04-11 at 23:39 +0800, Jia-Ju Bai wrote:
>> de4x5_hw_init() is never called in atomic context.
>>
>> de4x5_hw_init() is only called by de4x5_pci_probe(), which is only
>> set as ".probe" in struct pci_driver.
>>
>> Despite never getting called from atomic context, de4x5_hw_init()
>> calls mdelay() to busily wait. This is not necessary and can be
>> replaced with usleep_range() to avoid busy waiting.
>>
>> This is found by a static analysis tool named DCNS written by myself.
>> And I also manually check it.
> Did you actually test this? The usual reason for wanting m/udelay is
> that the timing must be exact. The driver is filled with mdelay()s for
> this reason. The one you've picked on is in the init path so it won't
> affect the runtime in any way. I also don't think we have the hrtimer
> machinery for usleep_range() to work properly on parisc, so I don't
> think the replacement works.
>
> James
>
Hello, James.
Thanks for your reply :)
I agree that usleep_range() here will not much affect the real execution
of this driver.
But I think usleep_range() can more opportunity for other threads to use
the CPU core to schedule during waiting.
That is why I detect mdelay() that can be replaced with msleep() or
usleep_range().
Best wishes,
Jia-Ju Bai
next prev parent reply other threads:[~2018-04-12 1:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-11 15:39 [PATCH v2] dec: tulip: de4x5: Replace mdelay with usleep_range in de4x5_hw_init Jia-Ju Bai
2018-04-11 16:16 ` James Bottomley
2018-04-12 1:30 ` Jia-Ju Bai [this message]
2018-04-12 2:21 ` arvindY
2018-04-12 2:26 ` Jia-Ju Bai
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=8bac3385-97c6-fff1-17c6-11f5e98a039a@gmail.com \
--to=baijiaju1990@gmail.com \
--cc=James.Bottomley@HansenPartnership.com \
--cc=arvind.yadav.cs@gmail.com \
--cc=davem@davemloft.net \
--cc=dhowells@redhat.com \
--cc=johannes.berg@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-parisc@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=stephen@networkplumber.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).