http://www.python.org/dev/buildbot/all/builders/x86%20FreeBSD%206.4%203.x/builds/1734/steps/test/logs/stdio

"""
======================================================================
ERROR: test_get_and_set_scheduler_and_param (test.test_posix.PosixTester)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/db3l/buildarea/3.x.bolen-freebsd/build/Lib/test/test_posix.py", line 878, in test_get_and_set_scheduler_and_param
    posix.sched_setparam(0, param)
OSError: [Errno 22] Invalid argument

----------------------------------------------------------------------
"""

The reason is quite simple:

http://freebsd.active-venture.com/FreeBSD-srctree/newsrc/posix4/ksched.c.html

"""
/*
 * XXX About priorities
 *
 *	POSIX 1003.1b requires that numerically higher priorities be of
 *	higher priority.  It also permits sched_setparam to be
 *	implementation defined for SCHED_OTHER.  I don't like
 *	the notion of inverted priorites for normal processes when
 *  you can use "setpriority" for that.
 *
 *	I'm rejecting sched_setparam for SCHED_OTHER with EINVAL.
 */

[...]
int ksched_setparam(register_t *ret, struct ksched *ksched,
	struct proc *p, const struct sched_param *param)
{
	register_t policy;
	int e;

	e = getscheduler(&policy, ksched, p);

	if (e == 0)
	{
		if (policy == SCHED_OTHER)
			e = EINVAL;
		else
			e = ksched_setscheduler(ret, ksched, p, policy, param);
	}

	return e;
}

"""

And indeed, sched_setparam is implementation-defined if the process' scheduling policy is SCHED_OTHER, see http://pubs.opengroup.org/onlinepubs/007908799/xsh/sched_setparam.html
"""
If the current scheduling policy for the process specified by pid is not SCHED_FIFO or SCHED_RR, including SCHED_OTHER, the result is implementation-dependent.
"""

It seems that FreeBSD made the choice of returning EINVAL, but it changed in recent versions (the test passes on FreeBSD 8).

I'm not sure about the best solution though:
1) don't perform this test if the scheduling policy is not SCHED_RR or SCHED_FIFO
2) skip this test on FreeBSD versions that return EINVAL (maybe adding a new requires_freebsd_version to test.support)

Here's a patch skipping this part of the test on FreeBSD (it actually also fails on FreeBSD 7.2).
Note that while calling sched_setparam(param) results in EINVAL with SCHED_OTHER processes, calling sched_setscheduler(SCHED_OTHER, param) works just fine...

Sounds fine to me.

New changeset a04e70d7d76c by Charles-François Natali in branch 'default':
Issue #12783: Fix test_posix failures on FreeBSD buildbots, due to
http://hg.python.org/cpython/rev/a04e70d7d76c

The test now passes on FreeBSD buildbots.
Closing.