Messages in this thread Patch in this message | | | Date | Mon, 17 Nov 2014 15:15:15 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 2/2] sched/deadline: Fix wrong cpudl_find() in check_preempt_equal_dl() |
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On Tue, 18 Nov 2014 00:11:04 +0800 "pang.xunlei" <pang.xunlei@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.xunlei@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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