linux-kernel - Re: [PATCH] arm: cmpxchg syscall should data abort if page not write or not young

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Message-ID: <AANLkTinekDMZUJSyOqOuPPpuoq49wFTzc1ESGqEdezzs@mail.gmail.com>
Date:	Tue, 15 Mar 2011 11:07:58 +0800
From:	Po-Yu Chuang <ratbert.chuang@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	tony@...mide.com, nicolas.pitre@...aro.org, joe@...ches.com,
	Po-Yu Chuang <ratbert@...aday-tech.com>
Subject: Re: [PATCH] arm: cmpxchg syscall should data abort if page not write
 or not young

Dear Russell King,

On Mon, Mar 14, 2011 at 6:40 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Mon, Mar 14, 2011 at 06:28:36PM +0800, Po-Yu Chuang wrote:
>> From: Po-Yu Chuang <ratbert@...aday-tech.com>
>>
>> If the page to cmpxchg is user mode read only (not write)
>> or invalid (not young), we should simulate a data abort first.
>
> No.  If it is not young then it should be made young.  Age is an effect
> of accesses.  It's not a permission.

OK, I will rethink about the not young part.
Thanks for your pointer.

I will resubmit a v2 which contains only the read only check.
It fixes a problem we met with futex.

best regards,
Po-Yu Chuang
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