linux-kernel - Re: Re: [PATCH] futex: bugfix for futex-key conflict when futex use hugepage

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Message-ID: <OF79A40956.94F46B9C-ON48257B50.00320F73-48257B50.0036925D@zte.com.cn>
Date:	Wed, 17 Apr 2013 17:55:29 +0800
From:	zhang.yi20@....com.cn
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Re: [PATCH] futex: bugfix for futex-key conflict when futex use
 hugepage

Darren Hart <dvhart@...ux.intel.com> wrote on 2013/04/17 01:57:10:

> Again, a functional testcase in futextest would be a good idea. This
> helps validate the patch and also can be used to identify regressions in
> the future.

I will post the testcase code later.

> 
> What is the max value of comp_idx? Are we at risk of truncating it?
> Looks like not really from my initial look.
> 
> This also needs a comment in futex.h describing the usage of the offset
> field in union futex_key as well as above get_futex_key describing the
> key for shared mappings.
> 
> 

As far as I know , the max size of one hugepage is 1 GBytes for x86 cpu.
Can some other cpus support greater hugepage even more than 4 GBytes? If 
so, we can change the type of 'offset' from int to long to avoid 
truncating.
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