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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: No timed lock on MacOS
Date Wed, 05 Apr 2017 17:02:34 GMT
Am 05.04.2017 um 16:25 schrieb Branko ─îibej:
> On 05.04.2017 14:16, Jim Jagielski wrote:
>> Hmmm.... Looking over the timed stuff, it seems that semtimedop()
>> is used incorrectly.
>>
>> For both pthread_mutex_timedlock() and sem_timedwait(), the
>> timeout variable is the actual wallclock time that the wait
>> expires (eg: now+5mins). But, from what I can read about semtimedop(), its
>> timeout really is a timeout (5mins). But it seems that we use it
>> as if it was wall-clock time, which is WAY wrong...
>>
>> Can someone check to see what exactly the timeout value is for
>> semtimedop()? Is it a delta or a wall-clock?
>
>
> My man page says:
>
>     semtimedop() behaves identically to semop() except that in those
>     cases where the calling thread would sleep, the duration of that
>     sleep is limited by the amount of elapsed time specified by the
>     timespec structure whose address is passed in the timeout argument.
>
>
> Looks like delta to me.

Solaris man page. Those are typically good:

      The semtimedop() function behaves as semop() except when  it
      must  suspend  execution  of the calling process to complete
      its operation.  If semtimedop()  must  suspend  the  calling
      process   after  the  time  interval  specified  in  timeout
                            ^^^^^^^^^^^^^^
      expires, or if the timeout  expires  while  the  process  is
      suspended,  semtimedop()  returns  with  an  error.  If  the
      timespec structure pointed to by timeout is zero-valued  and
      semtimedop()  needs  to  suspend the calling process to com-
      plete the requested  operation(s),  it  returns  immediately
      with  an error. If timeout is the NULL pointer, the behavior
      of semtimedop() is identical to that of semop().

So they speak of a timeout interval, which also makes "delta" the likely 
interpretation.

Rainer

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