linux-kernel - Re: Change in functionality of futex() system call.

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Message-ID: <4DF037C6.4000507@linux.intel.com>
Date:	Wed, 08 Jun 2011 20:02:30 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	George Spelvin <linux@...izon.com>
CC:	david@...advisors.com, kyle@...fetthome.net, luto@....edu,
	linux-kernel@...r.kernel.org
Subject: Re: Change in functionality of futex() system call.

On 06/08/2011 05:44 PM, George Spelvin wrote:
> I'm not sure if it's best, but the risk of RO waiters interfering could
> be solved by giving them a lower prioirty for wakeup and always waking
> RW-mapped waiters first.

This strikes me as bending over backwards and jumping through hoops
inside the kernel to avoid having to do proper permissions management in
userspace.


> In most cases, there would only be one type of waiter, so this would
> have no effect, but if there were, a RO-mapped reader couldn't "steal"
> wakeup from someone who had it RW-mapped.
> 
> It might conflict with a fairness goal, but it does solve the problem
> without any extension to the API.

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel
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