Messages in this thread Patch in this message |  | | Date | Thu, 9 Apr 2015 09:56:38 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH v5 2/3] sched/rt: Fix wrong SMP scheduler behavior for equal prio cases |
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On Thu, 9 Apr 2015 11:27:17 +0800 Xunlei Pang <xlpang@126.com> wrote:
> Suggested-by: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org> > --- > kernel/sched/rt.c | 26 ++++++++++++++++++++------ > 1 file changed, 20 insertions(+), 6 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 575da76..402162a 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -359,11 +359,15 @@ static inline void set_post_schedule(struct rq *rq) > rq->post_schedule = has_pushable_tasks(rq); > } > > -static void enqueue_pushable_task(struct rq *rq, struct task_struct *p) > +static void > +enqueue_pushable_task(struct rq *rq, struct task_struct *p, bool head) > { > plist_del(&p->pushable_tasks, &rq->rt.pushable_tasks); > plist_node_init(&p->pushable_tasks, p->prio); > - plist_add(&p->pushable_tasks, &rq->rt.pushable_tasks); > + if (head) > + plist_add_head(&p->pushable_tasks, &rq->rt.pushable_tasks); > + else > + plist_add_tail(&p->pushable_tasks, &rq->rt.pushable_tasks); > > /* Update the highest prio pushable task */ > if (p->prio < rq->rt.highest_prio.next) > @@ -385,7 +389,8 @@ static void dequeue_pushable_task(struct rq *rq, struct task_struct *p) > > #else > > -static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p) > +static inline > +void enqueue_pushable_task(struct rq *rq, struct task_struct *p, bool head) > { > } > > @@ -1260,7 +1265,7 @@ enqueue_task_rt(struct rq *rq, struct task_struct *p, int flags) > enqueue_rt_entity(rt_se, flags & ENQUEUE_HEAD); > > if (!task_current(rq, p) && p->nr_cpus_allowed > 1) > - enqueue_pushable_task(rq, p); > + enqueue_pushable_task(rq, p, false);
Hmm, I really don't like the "false" parameter all over the place, since it's only needed in one place. Thinking about this more, what about keeping enqueue_pushable_task() as is, and adding an enqueue_pushable_task_preempted(). Having something like this:
static inline void enqueue_pushable_task(struct rq *rq, struct task_struct *p) { enqueue_pushable_task_preempted(rq, p, false); }
> } > > static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int flags) > @@ -1507,7 +1512,16 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p) > * if it is still active > */ > if (on_rt_rq(&p->rt) && p->nr_cpus_allowed > 1) > - enqueue_pushable_task(rq, p); > + /* > + * put_prev_task_rt() is called by many functions, > + * pick_next_task_rt() is the only one may have > + * PREEMPT_ACTIVE set. So if detecting p(current > + * task) is preempted in such case, we should > + * enqueue it to the front of the pushable plist, > + * as there may be multiple tasks with the same > + * priority as p. > + */ > + enqueue_pushable_task(rq, p, !!(preempt_count() & PREEMPT_ACTIVE));
Then we don't need to touch any of the code but this place, and this would be:
enqueue_pushable_task_preempted(rq, p, !!(preempt_count() & PREEMPT_ACTIVE));
I'm thinking this would be much more descriptive.
What do you think?
-- Steve
> } > #ifdef CONFIG_SMP > @@ -2091,7 +2105,7 @@ static void set_cpus_allowed_rt(struct task_struct *p, > rq->rt.rt_nr_migratory--; > } else { > if (!task_current(rq, p)) > - enqueue_pushable_task(rq, p); > + enqueue_pushable_task(rq, p, false); > rq->rt.rt_nr_migratory++; > } >
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