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Message-ID: <20100727113133.1605c9fe@bike.lwn.net> Date: Tue, 27 Jul 2010 11:31:33 -0600 From: Jonathan Corbet <corbet@....net> To: Israel Schlesinger <israels@...eaurora.org> Cc: linux-kernel@...r.kernel.org, apw@...onical.com, akpm@...ux-foundation.org, joe@...ches.com Subject: Re: [PATCH] checkpatch: Add warnings for use of mdelay() On Tue, 27 Jul 2010 10:11:11 -0700 Israel Schlesinger <israels@...eaurora.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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