Does POSIX standard say EXPLICIT or IMPLICIT SCHED

[Till Straumann]

I guess I was naive when I first wrote the benchmark code - I figured 
POSIX was a standard
and hence the defaults would be standardized.

After discovering the problem, yesterday I did a similar research and 
came to the same
conclusion: it seems that the defaults set by pthread_attr_init() are 
implementation dependent.

Here are more examples:
IBM AIX unix uses INHERIT_SCHED by default, IBM OS/400's default is 
EXPLICIT_SCHED
;-)

-- Till

Ralf Corsepius wrote:

>Am Mit, 2002-12-04 um 16.48 schrieb Joel Sherrill:
>  
>
>>>>My benchmark code fails to set PTHREAD_EXPLICIT_SCHED and hence
>>>>the benchmark task runs at the wrong priority. I had developed the
>>>>pthread stuff for RT-Linux (where EXPLICIT_SCHED is the default,
>>>>as it is on some other systems, it seems).
>>>>        
>>>>
>>>I searched some last night
>>>      
>>>
>>and unfortunately did not complete this paragraph.  :(
>>
>>I looked to see what the POSIX or OpenGroup standards say about this
>>and didn't find anything which gave me a clue.
>>    
>>
>
>>From SUSV3/pthread_attr_init():
>
>The pthread_attr_init() function shall initialize a thread attributes
>object attr with the default value for all of the individual attributes
>used by a given implementation.
>
>I read this as being "explicitly unspecific", i.e. "everything is
>implementation-defined".
>
>  
>
>>  Does anyone out there
>>know what The Right Thing To Do (TM) is?
>>    
>>
>IMO: "You must not rely on any implicit defaults".
>
>
>Anyway, from  Solaris-2.7's pthread_attr_init's man-page:
>
>     The pthread_attr_init() function initializes a thread attri-
>     butes  object ( attr) with the default value for each attri-
>     bute as follows:
>
>        Attribute           Default Value                Meaning of Default
>     contentionscope   PTHREAD_SCOPE_PROCESS     resource competition within process
>     detachstate       PTHREAD_CREATE_JOINABLE   joinable by other threads
>     stackaddr         NULL                      stack allocated by system
>     stacksize         NULL                      1 or 2 megabyte
>     priority          0                         priority of the thread
>     policy            SCHED_OTHER               determined by system
>     inheritsched      PTHREAD_EXPLICIT_SCHED    scheduling  policy  and  parameters
>                                                 not    inherited   but   explicitly
>                                                 defined by the attribute object
>     guardsize         PAGESIZE                  size of guard area for a  thread's
>                                                 created stack
>
>Linux pthread_attr_init man-page
>
>   inheritsched
>       Indicate whether the scheduling policy and  scheduling  parameters  for
>       the  newly created thread are determined by the values of the schedpol-
>       icy and schedparam attributes  (value  PTHREAD_EXPLICIT_SCHED)  or  are
>       inherited from the parent thread (value PTHREAD_INHERIT_SCHED).
> 
>       Default value: PTHREAD_EXPLICIT_SCHED.
>
>Ralf
>
>
>  
>