linux-kernel - Re: [PATCH] futex: cmpxchg_futex_value

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Date:	Thu, 10 Mar 2011 19:55:05 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Michel Lespinasse <walken@...gle.com>
cc:	Darren Hart <darren@...art.com>, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Matt Turner <mattst88@...il.com>,
	Russell King <linux@....linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Tony Luck <tony.luck@...el.com>,
	Michal Simek <monstr@...str.eu>,
	Ralf Baechle <ralf@...ux-mips.org>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Paul Mundt <lethal@...ux-sh.org>,
	"David S. Miller" <davem@...emloft.net>,
	Chris Metcalf <cmetcalf@...era.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] futex: cmpxchg_futex_value_locked API change

On Wed, 9 Mar 2011, Michel Lespinasse wrote:
> On Tue, Mar 08, 2011 at 09:17:11PM +0100, Thomas Gleixner wrote:

Just looked at it again in detail before picking it up. Can we please
separate the s/int/u32/ changes from the real API change ?

>  
> -	pagefault_disable();	/* implies preempt_disable() */
> +	/* Note that preemption is disabled by futex_atomic_cmpxchg_inatomic
> +	 * call sites. */

That wants to be a separate patch as well.
  
> -int futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
> +int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
>  {
>  	int op = (encoded_op >> 28) & 7;
>  	int cmp = (encoded_op >> 24) & 15;
> @@ -197,7 +197,7 @@ int futex_atomic_op_inuser(int encoded_op, int __user *uaddr)
>  	if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
>  		oparg = 1 << oparg;
>  
> -	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int)))
> +	if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32)))
>  		return -EFAULT;
>  
>  	pagefault_disable();

So following the reasoning above, shouldn't that be the same for
futex_atomic_op_inuser() ?

Thanks,

	tglx
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