[PATCH 2/2] ARM: futex: make futex_detect_cmpxchg more reliable

Russell King - ARM Linux admin linux at armlinux.org.uk
Fri Mar 8 01:54:07 PST 2019


On Thu, Mar 07, 2019 at 04:04:23PM -0800, Nick Desaulniers wrote:
> On Thu, Mar 7, 2019 at 3:49 PM Russell King - ARM Linux admin
> <linux at armlinux.org.uk> wrote:
> >
> > On Thu, Mar 07, 2019 at 11:39:08AM -0800, Nick Desaulniers wrote:
> > > Underspecification of constraints to extended inline assembly is a
> > > common issue exposed by other compilers (and possibly but in-effect
> > > infrequently compiler upgrades).
> >
> > I don't see what is "underspecified" in the original constraints.
> > Please explain.
> 
> From the link:
> 
> The problem is that in the T(streq) insn, %3 and %4 MUST be different registers,
> but nothing in the asm() constrains them to be different.

Thanks, but that is not what I'm asking.  See my reply to Ard.

-- 
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