Re: [Qemu-devel] [RFC 01/10] target-arm: protect cpu_exclusive_*.

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Richard Henderson (rth@twiddle.net) 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 / dgilbert@redhat.com / Manchester, UK