From: Patrick Pannuto <ppannuto@codeaurora.org>
To: Jonathan Corbet <corbet@lwn.net>
Cc: Israel Schlesinger <israels@codeaurora.org>,
linux-kernel@vger.kernel.org, apw@canonical.com,
akpm@linux-foundation.org, joe@perches.com
Subject: Re: [PATCH] checkpatch: Add warnings for use of mdelay()
Date: Tue, 27 Jul 2010 10:32:54 -0700 [thread overview]
Message-ID: <4C4F1846.3090103@codeaurora.org> (raw)
In-Reply-To: <20100727113133.1605c9fe@bike.lwn.net>
On 07/27/2010 10:31 AM, Jonathan Corbet wrote:
> On Tue, 27 Jul 2010 10:11:11 -0700
> Israel Schlesinger <israels@codeaurora.org> wrote:
>
>> mdelay is a busy-wait loop which is wasteful. If at all possible,
>> callers should use msleep instead of mdelay.
>>
>> The only time mdelay is really appropriate is in atomic context,
>> however, delays of 1ms+ in atomic context are rather expensive, so
>> a warning for this case is probably appropriate as well to encourage
>> people to move such expensive delays outside of atomic context
>
> Once upon a time, msleep(1) would sleep for 20ms, while mdelay(1) gave
> a 1ms delay. My patch to fix msleep() at that time didn't get in due
> to concerns about the cost of using hrtimers. Perhaps msleep() has
> gotten better, but, if not, actually getting a 1ms delay remains a
> valid reason for using mdelay() instead IMO. It made a difference of a
> few seconds at open time for a driver I was doing at the time.
>
> jon
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> Please read the FAQ at http://www.tux.org/lkml/
Check out the recently added usleep in -tip, and the checkpatch patch
pending in my queue that fixes that case (I'll send in a few hours ;) )
-pat
--
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum
next prev parent reply other threads:[~2010-07-27 17:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-27 17:11 [PATCH] checkpatch: Add warnings for use of mdelay() Israel Schlesinger
2010-07-27 17:22 ` Joe Perches
2010-07-27 17:31 ` Jonathan Corbet
2010-07-27 17:32 ` Patrick Pannuto [this message]
2010-07-27 19:16 ` Andrew Morton
2010-07-28 9:44 ` Andy Whitcroft
2018-07-04 18:18 Prakruthi Deepak Heragu
2018-07-04 18:30 ` Joe Perches
2018-07-05 8:19 ` Dan Carpenter
2018-07-06 5:49 ` Julia Lawall
2018-07-07 12:09 ` Jia-Ju Bai
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