linux-kernel - Re: [PATCH] hrtimers: Special-case zero length sleeps

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Message-ID: <20120216142733.GA15632@srcf.ucam.org>
Date:	Thu, 16 Feb 2012 14:27:33 +0000
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] hrtimers: Special-case zero length sleeps

On Wed, Feb 15, 2012 at 08:47:57PM +0000, Matthew Garrett wrote:

> Ok. I'll work on finding how prevelant it is and see if we can kill it 
> off in userspace.

Checking through an exploded Fedora kernel tree suggests around 125 
packages out of 11000 or so, so around 1% of userspace seems to use 
sleep(0) under certain circumstances. We can probably fix everything in 
the distribution, but that suggests that there's also going to be a 
significant amount of code in the outside world that's also broken. 

Userspace clearly has an expectation that sleep(0) is magic in some 
ill-defined way. We'd be well within our rights to break that 
expectation, but I think it's common enough to warrant special casing.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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