From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 01/29] asm-generic: add generic futex for
 !CONFIG_SMP
Date: Tue, 23 Sep 2014 23:47:59 +0200 (CEST)
Message-ID: <alpine.DEB.2.10.1409232335500.4604@nanos>
References: <1410168160-3624-1-git-send-email-lftan@altera.com> <1410168160-3624-2-git-send-email-lftan@altera.com> <CAFiDJ5-b_P7aWFXYP4GcgTUb3t_j6dZCsjeGZwVUs+7qo0v-GA@mail.gmail.com>
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On Tue, 23 Sep 2014, LF.Tan wrote:
> On Mon, Sep 8, 2014 at 5:22 PM, Ley Foon Tan <lftan@altera.com> wrote:
> > Follow m68k futex implementation for !CONFIG_SMP.

Great. Follow arch/random implementation blindly and copy all the bugs
in it.

> > +static inline int
> > +futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
> > +                             u32 oldval, u32 newval)
> > +{
> > +       u32 val;
> > +
> > +       if (unlikely(get_user(val, uaddr) != 0))
> > +               return -EFAULT;
> > +
> > +       if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
> > +               return -EFAULT;
> > +
> > +       *uval = val;
> > +
> > +       return 0;
> > +}

Care to explain how this works reliably and resembles proper cmpxchg
semantics under all circumstances?

Thanks,

	tglx

From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Tue, 23 Sep 2014 23:47:59 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH v3 01/29] asm-generic: add generic futex for
 !CONFIG_SMP
In-Reply-To: <CAFiDJ5-b_P7aWFXYP4GcgTUb3t_j6dZCsjeGZwVUs+7qo0v-GA@mail.gmail.com>
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References: <1410168160-3624-1-git-send-email-lftan@altera.com> <1410168160-3624-2-git-send-email-lftan@altera.com> <CAFiDJ5-b_P7aWFXYP4GcgTUb3t_j6dZCsjeGZwVUs+7qo0v-GA@mail.gmail.com>
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Message-ID: <20140923214759.Qgm82WcGpYpT7nAJ3m_VAz15o1geod0YnPgXbcqpgwA@z>

On Tue, 23 Sep 2014, LF.Tan wrote:
> On Mon, Sep 8, 2014 at 5:22 PM, Ley Foon Tan <lftan@altera.com> wrote:
> > Follow m68k futex implementation for !CONFIG_SMP.

Great. Follow arch/random implementation blindly and copy all the bugs
in it.

> > +static inline int
> > +futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
> > +                             u32 oldval, u32 newval)
> > +{
> > +       u32 val;
> > +
> > +       if (unlikely(get_user(val, uaddr) != 0))
> > +               return -EFAULT;
> > +
> > +       if (val == oldval && unlikely(put_user(newval, uaddr) != 0))
> > +               return -EFAULT;
> > +
> > +       *uval = val;
> > +
> > +       return 0;
> > +}

Care to explain how this works reliably and resembles proper cmpxchg
semantics under all circumstances?

Thanks,

	tglx