Re: For review: pthread_attr_setinheritsched.3

[Michael Kerrisk <mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>]

Hi Loic,


> yet another review... Enough for today ;-)

And thanks once again!

[...]

>> .SH DESCRIPTION
>> The
>> .BR pthread_attr_setinheritsched ()
>> function sets the inherit scheduler attribute of the
>> thread attributes object referred to by
>> .IR thread
> 
> should be "attr"

Thanks; fixed.

[...]

>> .SH BUGS
>> As at glibc 2.8, if a thread attributes object is initialized using
>> .BR pthread_attr_init (3),
>> then the scheduling policy of the attributes object is set to
>> .BR SCHED_OTHER
>> and the scheduling priority is set to 0.
>> However, if the inherit scheduler attribute is then set to
>> .BR PTHREAD_EXPLICIT_SCHED ,
>> then a thread created using the attribute object
>> wrongly inherits its scheduling attributes from the creating thread.
>> This bug does not occur if either the scheduling policy or
>> scheduling priority attribute is explicitly set
>> in the thread attributes object before calling
>> .BR pthread_create (3).
>> .\" FIXME . Track status of the following bug:
>> .\" http://sourceware.org/bugzilla/show_bug.cgi?id=7007
> 
> You raised an interesting issue. I checked the code responsible for
> pthread_create(). As a matter of fact, Glibc shall only take the 
> explicit scheduling if either the policy or priority has been set.

Agreed, that is what I also determined from reading the code.

> This
> makes somehow sense: if you want explicit scheduling, you should at 
> least set one of the two parameters, shouldn't you?

Yes, except that there are defaults that can be inspected in the
attr object, and these defaults are not honored when a thread is
actually created.  That seems wrong to me.

> I was wondering how other Pthreads implementation behave in this case. 
> Did you discuss this topic on Austin?

I didn't raise this on Austin, but Solaris 8 does what I would expect.

Cheers,

Michael


-- 
Michael Kerrisk
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