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Re: [Qemu-devel] [RFC 01/10] target-arm: protect cpu_exclusive_*.
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 01/10] target-arm: protect cpu_exclusive_*. |
Date: |
Fri, 13 Mar 2015 20:04:06 +0000 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
* Richard Henderson (address@hidden) wrote:
> On 03/03/2015 07:47 AM, Dr. David Alan Gilbert wrote:
> > That works for ARM where you have to terminate a ldrex with a strex or
> > clrex,
> > but not all architectures have the equivalent of a clrex; most as I remember
> > just let you do an ldrex equivalent, decide you don't want to do the strex
> > equivalent
> > and get on with life.
>
>
> I'm pretty sure that's not the case. In fact, I can guarantee you that GCC
> never issues clrex, but does in fact simply do nothing like you describe for
> other architectures if we decide not to do the store.
Oh well, that means this technique won't work even for ARM, where I thought
it might stand a chance for ARM but nothing else.
I've still got a vague memory that some ARM docs at one point told you that
you should terminate an LDREX by either an STREX or a CLREX; but it's ~3.5 years
since I did any arm wrestling.
Dave
> r~
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK