Peter Zijlstra wrote:
On Thu, 2009-03-12 at 06:53 -0700, Arjan van de Ven wrote:Darren Hart wrote:Commit-ID: 16f4993f4e9860715918efd4eeac928f8de1218b Gitweb: http://git.kernel.org/tip/16f4993f4e9860715918efd4eeac928f8de1218b Author: "Darren Hart" <dvhltc@xxxxxxxxxx> AuthorDate: Thu, 12 Mar 2009 00:55:59 -0700 Commit: Ingo Molnar <mingo@xxxxxxx> CommitDate: Thu, 12 Mar 2009 11:20:57 +0100 futex: use current->time_slack_ns for rt tasks too RT tasks should set their timer slack to 0 on their own. This patch removes the 'if (rt_task()) slack = 0;' block in futex_wait.Hi, can you explain the rationale for this reasoning?Yeah, I found it iffy as well, I think we want something like the below instead though.. --- Subject: sched: adjust timer_slack_ns on scheduler policy change From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Date: Thu Mar 12 15:01:02 CET 2009 Ensure RT tasks have 0 timer slack.
Fork takes care of this by setting the child's default_timer_slack_ns to current->timer_slack_ns. This change takes care of tasks that are converted to rt by the user.
What about tasks that are demoted from RT to SCHED_NORMAL? I'm not sure setting it to the default_timer_slack_ns is the right thing since that could have been the timer_slack_ns of the rt process it forked from. Perhaps heach scheduler class needs to have a default_timer_slack_ns set in the class?
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> --- kernel/sched.c | 2 ++ 1 file changed, 2 insertions(+) Index: linux-2.6/kernel/sched.c =================================================================== --- linux-2.6.orig/kernel/sched.c +++ linux-2.6/kernel/sched.c @@ -5511,10 +5511,12 @@ __setscheduler(struct rq *rq, struct tas case SCHED_NORMAL: case SCHED_BATCH: case SCHED_IDLE: + p->timer_slack_ns = p->default_timer_slack_ns; p->sched_class = &fair_sched_class; break; case SCHED_FIFO: case SCHED_RR: + p->timer_slack_ns = 0; p->sched_class = &rt_sched_class; break; }
-- Darren Hart IBM Linux Technology Center Real-Time Linux Team -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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