Merge "sched: avoid scheduling RT threads on cores currently handling softirqs" (75cfe59d) · Commits · e / devices / android_kernel_oneplus_sm8150

kernel/sched/cpupri.c

+35 −2

Original line number	Diff line number	Diff line
		@@ -27,6 +27,8 @@
		* of the License.
		*/

		#include "sched.h"

		#include <linux/gfp.h>
		#include <linux/sched.h>
		#include <linux/sched/rt.h>
		@@ -50,6 +52,27 @@ static int convert_prio(int prio)
		return cpupri;
		}

		/**
		* drop_nopreempt_cpus - remove a cpu from the mask if it is likely
		* non-preemptible
		* @lowest_mask: mask with selected CPUs (non-NULL)
		*/
		static void
		drop_nopreempt_cpus(struct cpumask *lowest_mask)
		{
		unsigned int cpu = cpumask_first(lowest_mask);

		while (cpu < nr_cpu_ids) {
		/* unlocked access */
		struct task_struct *task = READ_ONCE(cpu_rq(cpu)->curr);

		if (task_may_not_preempt(task, cpu))
		cpumask_clear_cpu(cpu, lowest_mask);

		cpu = cpumask_next(cpu, lowest_mask);
		}
		}

		/**
		* cpupri_find - find the best (lowest-pri) CPU in the system
		* @cp: The cpupri context
		@@ -70,9 +93,11 @@ int cpupri_find(struct cpupri cp, struct task_struct p,
		{
		int idx = 0;
		int task_pri = convert_prio(p->prio);
		bool drop_nopreempts = task_pri <= MAX_RT_PRIO;

		BUG_ON(task_pri >= CPUPRI_NR_PRIORITIES);

		retry:
		for (idx = 0; idx < task_pri; idx++) {
		struct cpupri_vec *vec = &cp->pri_to_cpu[idx];
		int skip = 0;
		@@ -108,7 +133,8 @@ int cpupri_find(struct cpupri cp, struct task_struct p,

		if (lowest_mask) {
		cpumask_and(lowest_mask, &p->cpus_allowed, vec->mask);

		if (drop_nopreempts)
		drop_nopreempt_cpus(lowest_mask);
		/*
		* We have to ensure that we have at least one bit
		* still set in the array, since the map could have
		@@ -123,7 +149,14 @@ int cpupri_find(struct cpupri cp, struct task_struct p,

		return 1;
		}

		/*
		* If we can't find any non-preemptible cpu's, retry so we can
		* find the lowest priority target and avoid priority inversion.
		*/
		if (drop_nopreempts) {
		drop_nopreempts = false;
		goto retry;
		}
		return 0;
		}

kernel/sched/rt.c

+36 −6

Original line number	Diff line number	Diff line
		@@ -6,6 +6,7 @@

		#include "sched.h"

		#include <linux/interrupt.h>
		#include <linux/slab.h>
		#include <linux/irq_work.h>

		@@ -1450,12 +1451,27 @@ static void yield_task_rt(struct rq *rq)
		#ifdef CONFIG_SMP
		static int find_lowest_rq(struct task_struct *task);

		/*
		* Return whether the task on the given cpu is currently non-preemptible
		* while handling a softirq or is likely to block preemptions soon because
		* it is a ksoftirq thread.
		*/
		bool
		task_may_not_preempt(struct task_struct *task, int cpu)
		{
		struct task_struct *cpu_ksoftirqd = per_cpu(ksoftirqd, cpu);

		return (task_thread_info(task)->preempt_count & SOFTIRQ_MASK) \|\|
		task == cpu_ksoftirqd;
		}

		static int
		select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags,
		int sibling_count_hint)
		{
		struct task_struct *curr;
		struct rq *rq;
		bool may_not_preempt;

		/* For anything but wake ups, just return the task_cpu */
		if (sd_flag != SD_BALANCE_WAKE && sd_flag != SD_BALANCE_FORK)
		@@ -1467,7 +1483,17 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags,
		curr = READ_ONCE(rq->curr); /* unlocked access */

		/*
		* If the current task on @p's runqueue is an RT task, then
		* If the current task on @p's runqueue is a softirq task,
		* it may run without preemption for a time that is
		* ill-suited for a waiting RT task. Therefore, try to
		* wake this RT task on another runqueue.
		*
		* Also, if the current task on @p's runqueue is an RT task, then
		* it may run without preemption for a time that is
		* ill-suited for a waiting RT task. Therefore, try to
		* wake this RT task on another runqueue.
		*
		* Also, if the current task on @p's runqueue is an RT task, then
		* try to see if we can wake this RT task up on another
		* runqueue. Otherwise simply start this RT task
		* on its current runqueue.
		@@ -1488,18 +1514,22 @@ select_task_rq_rt(struct task_struct *p, int cpu, int sd_flag, int flags,
		* This test is optimistic, if we get it wrong the load-balancer
		* will have to sort it out.
		*/
		if (energy_aware() \|\|
		(curr && unlikely(rt_task(curr)) &&
		may_not_preempt = task_may_not_preempt(curr, cpu);
		if (energy_aware() \|\| may_not_preempt \|\|
		(unlikely(rt_task(curr)) &&
		(curr->nr_cpus_allowed < 2 \|\|
		curr->prio <= p->prio))) {
		int target = find_lowest_rq(p);

		/*
		* Don't bother moving it if the destination CPU is
		* not running a lower priority task.
		* If cpu is non-preemptible, prefer remote cpu
		* even if it's running a higher-prio task.
		* Otherwise: Don't bother moving it if the
		* destination CPU is not running a lower priority task.
		*/
		if (target != -1 &&
		p->prio < cpu_rq(target)->rt.highest_prio.curr)
		(may_not_preempt \|\|
		p->prio < cpu_rq(target)->rt.highest_prio.curr))
		cpu = target;
		}
		rcu_read_unlock();

kernel/sched/sched.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -2279,6 +2279,11 @@ extern void set_rq_online (struct rq *rq);
		extern void set_rq_offline(struct rq *rq);
		extern bool sched_smp_initialized;

		/*
		* task_may_not_preempt - check whether a task may not be preemptible soon
		*/
		extern bool task_may_not_preempt(struct task_struct *task, int cpu);

		#else /* CONFIG_SMP */

		/*