Re: [PATCH 2/4] nptl: Use FUTEX_LOCK_PI2 when available

[Kurt Kanzenbach via Libc-alpha <libc-alpha@sourceware.org>]

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On Thu Aug 12 2021, Adhemerval Zanella wrote:
> On 12/08/2021 03:42, Kurt Kanzenbach wrote:
>> Hi Adhemerval,
>> 
>> thanks for the respin of this series. Just some minor comments below.
>> 
>> On Wed Aug 11 2021, Adhemerval Zanella wrote:
>>> This patch uses the new futex PI operation provided by Linux v5.14
>>> when it is required.
>>>
>>> The futex_lock_pi64() is moved to futex-internal.c (since it used on
>>> two different places and its code size might be large depending of the
>>> kernel configuration) and clockid is added as an argument.
>>>
>>> Co-authored-by: Kurt Kanzenbach <kurt@linutronix.de>
>>> ---
>>>  nptl/futex-internal.c             | 63 +++++++++++++++++++++++++++++++
>>>  nptl/pthread_mutex_lock.c         |  3 +-
>>>  nptl/pthread_mutex_timedlock.c    |  3 +-
>>>  sysdeps/nptl/futex-internal.h     | 54 +-------------------------
>>>  sysdeps/nptl/lowlevellock-futex.h |  1 +
>>>  5 files changed, 70 insertions(+), 54 deletions(-)
>>>
>>> diff --git a/nptl/futex-internal.c b/nptl/futex-internal.c
>>> index e74647a9d4..58605b2fca 100644
>>> --- a/nptl/futex-internal.c
>>> +++ b/nptl/futex-internal.c
>>> @@ -140,3 +140,66 @@ __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
>>>                                         abstime, private, true);
>>>  }
>>>  libc_hidden_def (__futex_abstimed_wait_cancelable64)
>>> +
>>> +int
>>> +__futex_lock_pi64 (int *futex_word, clockid_t clockid,
>>> +		   const struct __timespec64 *abstime, int private)
>>> +{
>>> +  int err;
>> 
>> Is the clockid check not needed?
>> 
>>   if (! lll_futex_supported_clockid (clockid))
>>     return EINVAL;
>
> The ___pthread_mutex_clocklock64() already checks it (as other functions that uses
> a clockid_t).  I also tested for invalid clocks on tst-mutexpi10.c.
>
> And I think that the check on __futex_abstimed_wait_common() is superfluous..

OK, I see.

Thanks,
Kurt

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