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Re: [PATCH] Protect _dl_profile_fixup data-dependency order [BZ #23690]

On 09/19/2018 09:59 PM, John David Anglin wrote:
> On 2018-09-19 8:16 PM, Carlos O'Donell wrote:
>>>    DL_FIXUP_VALUE_TYPE *resultp = &reloc_result->addr;
>>> +  DL_FIXUP_VALUE_TYPE value = atomic_load_acquire(resultp);
>> You are potentially requiring an atomic load of a structure whose size can be
>> an arbitrary size depending on machine and ABI design (64-bit fore 32-bit hppa,
>> and 128-bit for 64-bit ia64). These architectures might not have such wide
>> atomic operations, and ...
> We have implemented 64-bit atomic loads and stores for 32-bit hppa. They are not well tested but
> they might work.  They use floating point loads and stores, and kernel helper.  The code is pretty horrific :-(

We only need to use the fdesc->ip as the guard, so we don't really need the 64-bit
atomic, but other algorithms like the new pthread condvars can use them effectively
to accelerate and avoid 2 lws kernel helper calls and instead use 1 lws kernel helper
64-bit atomic.


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