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Re: [RFC] [PATCH] powerpc: Fix missing barriers in atomic_exchange_and_add_{acq,rel}
- From: Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Date: Tue, 25 Nov 2014 16:09:25 -0200
- 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> <1416929990 dot 1771 dot 211 dot camel at triegel dot csb>
On 25-11-2014 13:39, Torvald Riegel wrote:
> 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?
>
I will do it, thanks.