From: Michel Lespinasse <walken@google.com>
To: linux-ia64@vger.kernel.org
Subject: Re: [PATCH] [IA64] Fix futex_atomic_cmpxchg_inatomic()
Date: Fri, 13 Apr 2012 22:31:11 +0000 [thread overview]
Message-ID: <CANN689F97CA+0gaCVwpYsvun+yOHat9tFJGt-LOS+sc9nc7U9g@mail.gmail.com> (raw)
In-Reply-To: <a3bcb07f7bd1106089a51033a6c104562fb90f89.1334342735.git.tony.luck@intel.com>
On Fri, Apr 13, 2012 at 8:32 PM, Luck, Tony <tony.luck@intel.com> wrote:
> Michel Lespinasse cleaned up the futex calling conventions in
> commit 37a9d912b24f96a0591773e6e6c3642991ae5a70
> futex: Sanitize cmpxchg_futex_value_locked API
>
> But the ia64 implementation was subtly broken. Gcc does not know
> that register "r8" will be updated by the fault handler if the
> cmpxchg instruction takes an exception. So it feels safe in letting
> the initialization of r8 slide to after the cmpxchg. Result: we
> always return 0 whether the user address faulted or not.
>
> Fix by moving the initialization of r8 into the __asm__ code so
> gcc won't move it.
Looks good. Sorry for the trouble.
--
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
next prev parent reply other threads:[~2012-04-13 22:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-13 18:32 [PATCH] [IA64] Fix futex_atomic_cmpxchg_inatomic() Luck, Tony
2012-04-13 22:31 ` Michel Lespinasse [this message]
2012-04-15 21:19 ` Émeric Maschino
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