On Tue, 18 Nov 2014 00:11:04 +0800
"pang.xunlei" <pang.xun...@linaro.org> wrote:
> In check_preempt_equal_dl(), cpudl_find() is called with a NULL later_mask,
> thus cpudl_find() here doesn't check cpudl.free_cpus at all.
>
> This patch takles this issue by always passing a non-NULL cpumask to
> cpudl_find(),
> and assigns later_mask in this function.
>
> Signed-off-by: pang.xunlei <pang.xun...@linaro.org>
> ---
> kernel/sched/cpudeadline.c | 14 ++++++--------
> kernel/sched/deadline.c | 10 ++++++----
> 2 files changed, 12 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
> index 9a69353..623f7b5 100755
> --- a/kernel/sched/cpudeadline.c
> +++ b/kernel/sched/cpudeadline.c
> @@ -97,7 +97,7 @@ static inline int cpudl_maximum(struct cpudl *cp)
> * cpudl_find - find the best (later-dl) CPU in the system
> * @cp: the cpudl max-heap context
> * @p: the task
> - * @later_mask: a mask to fill in with the selected CPUs (or NULL)
> + * @later_mask: a mask to fill in with the selected CPUs (not NULL)
> *
> * Returns: int - best CPU (heap maximum if suitable)
> */
> @@ -107,16 +107,14 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
> int best_cpu = -1;
> const struct sched_dl_entity *dl_se = &p->dl;
>
> - if (later_mask && cpumask_and(later_mask, cp->free_cpus,
> - &p->cpus_allowed) && cpumask_and(later_mask,
> - later_mask, cpu_active_mask)) {
> + cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed);
> + if (cpumask_and(later_mask, later_mask, cp->free_cpus)) {
> best_cpu = cpumask_any(later_mask);
> goto out;
> - } else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
> - dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
> + } else if (cpumask_and(later_mask, cpumask_of(cpudl_maximum(cp)),
> + &p->cpus_allowed) && dl_time_before(dl_se->deadline,
> + cp->elements[0].dl)) {
> best_cpu = cpudl_maximum(cp);
> - if (later_mask)
> - cpumask_set_cpu(best_cpu, later_mask);
> }
>
OK, I need to make this a before/after, as patch format sucks in this
case.
before:
if (later_mask &&
cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
cpumask_and(later_mask, later_mask, cpu_active_mask)) {
best_cpu = cpumask_any(later_mask);
goto out;
} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
dl_time_before(dl_se->deadline, cp->elements[0].dl)) {
best_cpu = cpudl_maximum(cp);
if (later_mask)
cpumask_set_cpu(best_cpu, later_mask);
}
after:
cpumask_and(later_mask, cpu_active_mask, &p->cpus_allowed);
if (cpumask_and(later_mask, later_mask, cp->free_cpus)) {
best_cpu = cpumask_any(later_mask);
goto out;
} else if (cpumask_and(later_mask, cpumask_of(cpudl_maximum(cp)),
&p->cpus_allowed) && dl_time_before(dl_se->deadline,
cp->elements[0].dl)) {
best_cpu = cpudl_maximum(cp);
}
Again, the above else if is rather ugly. Note, if the first
cpumask_and() is zero, there's no reason to call cpumask_and() (which
could be expensive) the second time. Keep the two together with &&.
Also, I wouldn't convert the cpumask_test_cpu() to a cpumask_and(), as
I would think that would be more expensive to copy an entire mask
(think what happens when we have a thousand CPUs). Just doing a test,
and then if the test succeeds (remember, there's another test that
might fail after it), then just set the one bit.
--- Steve
> out:
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index bd83272..3ecf838 100755
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -965,14 +965,18 @@ out:
> return cpu;
> }
>
> +static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
> +
> static void check_preempt_equal_dl(struct rq *rq, struct task_struct *p)
> {
> + struct cpumask *later_mask =
> this_cpu_cpumask_var_ptr(local_cpu_mask_dl);
> +
> /*
> * Current can't be migrated, useless to reschedule,
> * let's hope p can move out.
> */
> if (rq->curr->nr_cpus_allowed == 1 ||
> - cpudl_find(&rq->rd->cpudl, rq->curr, NULL) == -1)
> + cpudl_find(&rq->rd->cpudl, rq->curr, later_mask) == -1)
> return;
>
> /*
> @@ -980,7 +984,7 @@ static void check_preempt_equal_dl(struct rq *rq, struct
> task_struct *p)
> * see if it is pushed or pulled somewhere else.
> */
> if (p->nr_cpus_allowed != 1 &&
> - cpudl_find(&rq->rd->cpudl, p, NULL) != -1)
> + cpudl_find(&rq->rd->cpudl, p, later_mask) != -1)
> return;
>
> resched_curr(rq);
> @@ -1167,8 +1171,6 @@ next_node:
> return NULL;
> }
>
> -static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask_dl);
> -
> static int find_later_rq(struct task_struct *task)
> {
> struct sched_domain *sd;
--
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