Moin, Moin,
yet another review... Enough for today ;-)
Cheers,
Loïc.
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.\" Copyright (c) 2008 Linux Foundation, written by Michael Kerrisk
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.TH PTHREAD_ATTR_SETINHERITSCHED 3 2008-11-06 "Linux" "Linux
Programmer's Manual"
.SH NAME
pthread_attr_setinheritsched, pthread_attr_getinheritsched \- set/get
inherit scheduler attribute in thread attributes object
.SH SYNOPSIS
.nf
.B #include <pthread.h>
.BI "int pthread_attr_setinheritsched(pthread_attr_t *" attr ,
.BI " int " inheritsched );
.BI "int pthread_attr_getinheritsched(pthread_attr_t *" attr ,
.BI " int *" inheritsched );
.sp
Compile and link with \fI\-pthread\fP.
.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"
to the value specified in
.IR inheritsched .
The inherit scheduler attribute determines whether a thread created using
the thread attributes object
.I attr
will inherit its scheduling attributes from the calling thread
or whether it will take them from
.IR attr .
The following values may be specified in
.IR inheritsched :
.TP
.B PTHREAD_INHERIT_SCHED
Threads that are created using
.I attr
inherit scheduling attributes from the creating thread;
the scheduling attributes in
.I attr
are ignored.
.TP
.B PTHREAD_EXPLICIT_SCHED
Threads that are created using
.I attr
take their scheduling attributes from the values specified
by the attributes object.
.\" FIXME what are the defaults for scheduler settings?
.PP
The default setting of the inherit scheduler attribute in
a newly initialized thread attributes object is
.BR PTHREAD_INHERIT_SCHED .
The
.BR pthread_attr_getinheritsched ()
returns the inherit scheduler attribute of the thread attributes object
.IR attr
in the buffer pointed to by
.IR inheritsched .
.SH RETURN VALUE
On success, these functions return 0;
on error, they return a non-zero error number.
.SH ERRORS
.BR pthread_attr_setinheritsched ()
can fail with the following error:
.TP
.B EINVAL
Invalid value in
.IR inheritsched .
.PP
POSIX.1-2001 also documents an optional
.B ENOTSUP
error ("attempt was made to set the attribute to an unsupported value") for
.BR pthread_attr_setinheritsched ().
.\" .SH VERSIONS
.\" Available since glibc 2.0.
.SH CONFORMING TO
POSIX.1-2001.
.SH EXAMPLE
See
.BR pthread_setschedparam (3).
.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. This
makes somehow sense: if you want explicit scheduling, you should at
least set one of the two parameters, shouldn't you?
I was wondering how other Pthreads implementation behave in this case.
Did you discuss this topic on Austin?
.SH SEE ALSO
.BR sched_setscheduler (2),
.BR pthread_attr_init (3),
.BR pthread_attr_setschedparam (3),
.BR pthread_attr_setschedpolicy (3),
.BR pthread_create (3),
.BR pthread_setschedparam (3),
.BR pthread_setschedprio (3),
.BR pthreads (7)
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