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Re: [RFC] [PATCH] powerpc: Fix missing barriers in atomic_exchange_and_add_{acq,rel}
- From: Torvald Riegel <triegel at redhat dot com>
- To: Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 25 Nov 2014 16:39:50 +0100
- Subject: Re: [RFC] [PATCH] powerpc: Fix missing barriers in atomic_exchange_and_add_{acq,rel}
- Authentication-results: sourceware.org; auth=none
- References: <1413921274 dot 8483 dot 65 dot camel at triegel dot csb> <54749B3D dot 5010806 at linux dot vnet dot ibm dot com>
On Tue, 2014-11-25 at 13:07 -0200, Adhemerval Zanella wrote:
> Hi Torvald,
>
> On 21-10-2014 17:54, Torvald Riegel wrote:
> > \
> > })
> > +#define atomic_exchange_and_add_acq(mem, value) \
> > + ({ \
> > + __typeof (*(mem)) __result2; \
> > + __result2 = atomic_exchange_and_add (mem, value); \
> > + atomic_read_barrier (); \
> > + __result2;
>
> Although it is not wrong by using a 'atomic_read_barrier' (lwsync), it adds a more
> expensive synchronization than required (isync). I would prefer if we use the
> already defined __arch_compare_and_exchange_val_[32|64]_[acq|rel] operations on powerpc.
That's fine with me. Do you want to go adapt and commit the patch
(given that you can test this easily I guess), or should I?