Re: [PATCH v4 2/3] sched/rt: Fix wrong SMP scheduler behavior for equal prio cases
On Mon, 16 Feb 2015 17:32:23 +0800 Xunlei Pang wrote: > From: Xunlei Pang > > Currently, SMP RT scheduler has some trouble in dealing with > equal prio cases. > > For example, in check_preempt_equal_prio(): > When RT1(current task) gets preempted by RT2, if there is a > migratable RT3 with same prio, RT3 will be pushed away instead > of RT1 afterwards, because RT1 will be enqueued to the tail of > the pushable list when going through succeeding put_prev_task_rt() > triggered by resched. This broke FIFO. > > Furthermore, this is also problematic for normal preempted cases > if there're some rt tasks queued with the same prio as current, > because current will be put behind these tasks in the pushable > queue. > > So, if a task is running and gets preempted by a higher priority > task (or even with same priority for migrating), this patch ensures > that it is put before any existing task with the same priority in > the pushable queue. > > Signed-off-by: Xunlei Pang I'd love to review this now, but unfortunately I need to get ready for my trip to Linux Collab. I'll get back to this next week. Feel free to ping me then. If I have time, I might review this while at the conference, but don't place any bets that I will. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [PATCH v4 2/3] sched/rt: Fix wrong SMP scheduler behavior for equal prio cases
On Mon, 16 Feb 2015 17:32:23 +0800 Xunlei Pang xlp...@126.com wrote: From: Xunlei Pang pang.xun...@linaro.org Currently, SMP RT scheduler has some trouble in dealing with equal prio cases. For example, in check_preempt_equal_prio(): When RT1(current task) gets preempted by RT2, if there is a migratable RT3 with same prio, RT3 will be pushed away instead of RT1 afterwards, because RT1 will be enqueued to the tail of the pushable list when going through succeeding put_prev_task_rt() triggered by resched. This broke FIFO. Furthermore, this is also problematic for normal preempted cases if there're some rt tasks queued with the same prio as current, because current will be put behind these tasks in the pushable queue. So, if a task is running and gets preempted by a higher priority task (or even with same priority for migrating), this patch ensures that it is put before any existing task with the same priority in the pushable queue. Signed-off-by: Xunlei Pang pang.xun...@linaro.org I'd love to review this now, but unfortunately I need to get ready for my trip to Linux Collab. I'll get back to this next week. Feel free to ping me then. If I have time, I might review this while at the conference, but don't place any bets that I will. -- Steve -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
