On Fri, Sep 21, 2018 at 03:22:03PM -0500, PierceGriffiths wrote:
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 625bc9897f62..443a1f235cfd 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -617,12 +617,8 @@ bool sched_can_stop_tick(struct rq *rq)
> * If there are more than one RR tasks, we need the tick to effect the
> * actual RR behaviour.
> */
> - if (rq->rt.rr_nr_running) {
> - if (rq->rt.rr_nr_running == 1)
> - return true;
> - else
> - return false;
> - }
> + if (rq->rt.rr_nr_running)
> + return rq->rt.rr_nr_running == 1;
>
> /*
> * If there's no RR tasks, but FIFO tasks, we can skip the tick, no
That one is OK I suppose.
> diff --git a/kernel/sched/cpufreq.c b/kernel/sched/cpufreq.c
> index 5e54cbcae673..a8fd4bd68954 100644
> --- a/kernel/sched/cpufreq.c
> +++ b/kernel/sched/cpufreq.c
> @@ -34,10 +34,7 @@ void cpufreq_add_update_util_hook(int cpu, struct
> update_util_data *data,
> void (*func)(struct update_util_data *data, u64 time,
> unsigned int flags))
> {
> - if (WARN_ON(!data || !func))
> - return;
> -
> - if (WARN_ON(per_cpu(cpufreq_update_util_data, cpu)))
> + if (WARN_ON(!data || !func || per_cpu(cpufreq_update_util_data, cpu)))
> return;
>
> data->func = func;
But I'm not a fan of this one. It mixes a different class of function
and the WARN condition gets too complicated. Its easier to have separate
warns.
> diff --git a/kernel/sched/cpupri.c b/kernel/sched/cpupri.c
> index daaadf939ccb..152c133e8247 100644
> --- a/kernel/sched/cpupri.c
> +++ b/kernel/sched/cpupri.c
> @@ -29,20 +29,16 @@
> #include "sched.h"
>
> /* Convert between a 140 based task->prio, and our 102 based cpupri */
> -static int convert_prio(int prio)
> +static int convert_prio(const int prio)
> {
> - int cpupri;
> -
> if (prio == CPUPRI_INVALID)
> - cpupri = CPUPRI_INVALID;
> + return CPUPRI_INVALID;
> else if (prio == MAX_PRIO)
> - cpupri = CPUPRI_IDLE;
> + return CPUPRI_IDLE;
> else if (prio >= MAX_RT_PRIO)
> - cpupri = CPUPRI_NORMAL;
> + return CPUPRI_NORMAL;
> else
> - cpupri = MAX_RT_PRIO - prio + 1;
> -
> - return cpupri;
> + return MAX_RT_PRIO - prio + 1;
The code looks even better if you leave out the last else.
> }
>
> /**
> @@ -95,10 +91,8 @@ int cpupri_find(struct cpupri *cp, struct task_struct *p,
> smp_rmb();
>
> /* Need to do the rmb for every iteration */
> - if (skip)
> - continue;
> -
> - if (cpumask_any_and(&p->cpus_allowed, vec->mask) >= nr_cpu_ids)
> + if (skip || cpumask_any_and(&p->cpus_allowed, vec->mask)
> + >= nr_cpu_ids)
> continue;
>
> if (lowest_mask) {
That just makes the code ugly for no reason.
> @@ -222,7 +216,7 @@ int cpupri_init(struct cpupri *cp)
> return 0;
>
> cleanup:
> - for (i--; i >= 0; i--)
> + while (--i >= 0)
> free_cpumask_var(cp->pri_to_cpu[i].mask);
> return -ENOMEM;
> }
> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
> index 2e2955a8cf8f..acf1b94669ad 100644
> --- a/kernel/sched/rt.c
> +++ b/kernel/sched/rt.c
> @@ -142,10 +142,12 @@ void free_rt_sched_group(struct task_group *tg)
> destroy_rt_bandwidth(&tg->rt_bandwidth);
>
> for_each_possible_cpu(i) {
> - if (tg->rt_rq)
> - kfree(tg->rt_rq[i]);
> - if (tg->rt_se)
> - kfree(tg->rt_se[i]);
> + /* Don't need to check if tg->rt_rq[i]
> + * or tg->rt_se[i] are NULL, since kfree(NULL)
> + * simply performs no operation
> + */
That's an invalid comment style.
> + kfree(tg->rt_rq[i]);
> + kfree(tg->rt_se[i]);
> }
>
> kfree(tg->rt_rq);
> @@ -1015,10 +1017,7 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq)
>
> BUG_ON(&rq->rt != rt_rq);
>
> - if (rt_rq->rt_queued)
> - return;
> -
> - if (rt_rq_throttled(rt_rq))
> + if (rt_rq->rt_queued || rt_rq_throttled(rt_rq))
> return;
>
> if (rt_rq->rt_nr_running) {
The compiler can do this transformation and the old code was simpler.
> @@ -1211,10 +1210,7 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se,
> struct rt_rq *rt_rq)
> */
> static inline bool move_entity(unsigned int flags)
> {
> - if ((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
> - return false;
> -
> - return true;
> + return !((flags & (DEQUEUE_SAVE | DEQUEUE_MOVE)) == DEQUEUE_SAVE)
> }
Again, I find the new code harder to read.
>
> @@ -2518,12 +2513,10 @@ static int tg_set_rt_bandwidth(struct task_group *tg,
> /*
> * Disallowing the root group RT runtime is BAD, it would disallow the
> * kernel creating (and or operating) RT threads.
> + *
> + * No period doesn't make any sense.
> */
> - if (tg == &root_task_group && rt_runtime == 0)
> - return -EINVAL;
> -
> - /* No period doesn't make any sense. */
> - if (rt_period == 0)
> + if ((tg == &root_task_group && !rt_runtime) || !rt_period)
> return -EINVAL;
>
> mutex_lock(&rt_constraints_mutex);
Again, far harder to read.
In short, while all the transformations are 'correct' the end result is
horrible. Please don't do this.
