Re: pthread_attr_setsched behaviour

[Siddhesh Poyarekar <siddhesh dot poyarekar at gmail dot com>]

OK, *now* I've added Michael Kerrisk to cc :)

Siddhesh

On 17 April 2013 18:19, Siddhesh Poyarekar <siddhesh@redhat.com> wrote:
> On Tue, Apr 16, 2013 at 03:32:11PM +0200, Manuel Traut wrote:
>> Hi,
>>
>> i just recognized, that calling:
>>
>> ret |= pthread_attr_setschedpolicy (..)
>> ret |= pthread_attr_setschedparam (..)
>> ret |= pthread_create (..)
>>
>> doesn't return an error and the values set by pthread_attr_setschedparam and
>> pthread_attr_setschedpolicy aren't applied to the thread.
>>
>> The APPLICATION USAGE of the functions say:
>>
>>    After  these attributes have been set, a thread can be created with the
>>    specified attributes using pthread_create(). Using these routines  does
>>    not affect the current running thread.
>>
>> So I didn't expect that I need to call:
>> pthread_attr_setinheritsched before pthread_create.
>>
>> I would like to improve the current behaviour, with a little patch;
>> please give me some directions...
>>
>> Is there a reason why e.g. pthread_attr_set_schedparam doesn't set
>> iattr->flags |= ATTR_FLAG_NOTINHERITSCHED
>
> The POSIX specification doesn't tell us that we ought to do this.  If
> we do, we might end up breaking compatibility.
>
>> Or is it better to return an error code in pthread_attr_setschedparam, etc if
>> ATTR_FLAG_NOTINHERITSCHED isn't set?
>
> This is wrong since one is allowed to set NOTINHERITSCHED after
> setschedparam.
>
>> If both is bad, at least the man page should mention the need of calling
>> pthread_attr_setinheritsched..
>
> This is the best option currently.  I've added Michael Kerrisk to cc;
> he maintains the man pages.
>
> Siddhesh



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