On 17/10/12 15:10, Gilles Chanteperdrix wrote:
On 10/17/2012 03:02 PM, Arnout Vandecappelle wrote:
On 17/10/12 14:32, Gilles Chanteperdrix wrote:
On 10/17/2012 01:28 PM, Arnout Vandecappelle wrote:
[snip]
and also rt_task_create() looks only at the mode parameter and ignores
the parent thread's affinity.
That does not look like an issue. Why should a task inherit its parent's
affinity.
I don't know if it should - it's not specified in the documentation. But
it is how posix threads behave.
Ok. That is an argument. But if an affinity is specified by the mode
argument, it should override the parent's affinity.
OK. Would you like me to refresh my patch?
[snip]
Note, by the way, that calling sched_setaffinity _after_ the task has
started
_will_ change the affinity (cfr. switchtest), but any calls _before_ the task
has started are ignored.
Well, if the thread is not created, how sched_setaffinity change its
affinity?
The (shadow) thread is created, but with a different cpuset than the
Linux thread. Or rather, the cpuset is changed by shadowing the thread.
Ok, misunderstanding again, for me, when you say "before the task has
started" clearly means that you are talking about a task created with
rt_task_create.
Yes, that's what I mean.
When you do:
CPU_SET(1, &cpuset);
sched_setaffinity(0, sizeof(cpuset), &cpuset);
rt_task_shadow(&task, "test", 99, 0);
then rt_task_shadow will migrate the thread from cpu 1 to cpu 0,
so it migrates twice overall (assuming Linux had started it on cpu 0).
When you do:
rt_task_shadow(&task, "test", 99, 0);
CPU_SET(1, &cpuset);
sched_setaffinity(0, sizeof(cpuset), &cpuset);
then sched_setaffinity will migrate the thread from cpu 0 to cpu 1.
My point was that it seems inconsistent that it makes a difference
in which order you shadow the task and you specify which cpu it should
run on.
Alternatively, you could document in rt_task_shadow that it will
implicitly migrate to the lowest CPU (even if that's not the one we're
currently executing on).
Regards,
Arnout
--
Arnout Vandecappelle arnout at mind be
Senior Embedded Software Architect +32-16-286540
Essensium/Mind http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
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