Commit a3c9f2da authored by Zhang Qiao's avatar Zhang Qiao Committed by Wenyu Huang
Browse files

sched: Introduce handle priority reversion mechanism 

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8MF4R


CVE: NA

--------------------------------

When online tasks occupy cpu long time, offline task will not get cpu
to run, the priority inversion issue may be triggered in this case.
If the above case occurs, we will unthrottle offline tasks and let its
get a chance to run.
When online tasks occupy cpu over 5s(defaule value), we will unthrottle
offline tasks and enter a msleep loop before exit to usermode util the
cpu goto idle.

Signed-off-by: default avatarZhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: default avatarWenyu Huang <huangwenyu5@huawei.com>
parent 1fe7493d

include/linux/resume_user_mode.h

+5 −0
Original line number Diff line number Diff line
@@ -59,6 +59,11 @@ static inline void resume_user_mode_work(struct pt_regs *regs) 
	blkcg_maybe_throttle_current();



	rseq_handle_notify_resume(NULL, regs);



#ifdef CONFIG_QOS_SCHED

	sched_qos_offline_wait();

#endif



}



#endif /* LINUX_RESUME_USER_MODE_H */

include/linux/sched.h

+7 −0
Original line number Diff line number Diff line
@@ -2460,6 +2460,13 @@ extern void sched_set_stop_task(int cpu, struct task_struct *stop); 


#ifdef CONFIG_QOS_SCHED

void sched_move_offline_task(struct task_struct *p);

void sched_qos_offline_wait(void);

int sched_qos_cpu_overload(void);

#else

static inline int sched_qos_cpu_overload(void)

{

	return 0;

}

#endif



#endif

kernel/sched/core.c

+3 −0
Original line number Diff line number Diff line
@@ -10018,6 +10018,9 @@ void __init sched_init(void) 
		 * We achieve this by letting root_task_group's tasks sit

		 * directly in rq->cfs (i.e root_task_group->se[] = NULL).

		 */

#ifdef CONFIG_QOS_SCHED

		init_qos_hrtimer(i);

#endif

		init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);

#endif /* CONFIG_FAIR_GROUP_SCHED */

kernel/sched/fair.c

+120 −1
Original line number Diff line number Diff line
@@ -57,6 +57,11 @@ 
#include "stats.h"

#include "autogroup.h"



#ifdef CONFIG_QOS_SCHED

#include <linux/delay.h>

#include <linux/resume_user_mode.h>

#endif



/*

 * The initial- and re-scaling of tunables is configurable

 *
@@ -133,6 +138,12 @@ int __weak arch_asym_cpu_priority(int cpu) 
#define QOS_THROTTLED	2



static DEFINE_PER_CPU_SHARED_ALIGNED(struct list_head, qos_throttled_cfs_rq);

static DEFINE_PER_CPU_SHARED_ALIGNED(struct hrtimer, qos_overload_timer);

static DEFINE_PER_CPU(int, qos_cpu_overload);

unsigned int sysctl_overload_detect_period = 5000;  /* in ms */

unsigned int sysctl_offline_wait_interval = 100;  /* in ms */

static int one_thousand = 1000;

static int hundred_thousand = 100000;

static int unthrottle_qos_cfs_rqs(int cpu);

#endif
@@ -184,6 +195,26 @@ static struct ctl_table sched_fair_sysctls[] = { 
		.extra1		= SYSCTL_ZERO,

	},

#endif /* CONFIG_NUMA_BALANCING */

#ifdef CONFIG_QOS_SCHED

	{

		.procname	= "qos_overload_detect_period_ms",

		.data		= &sysctl_overload_detect_period,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ONE_HUNDRED,

		.extra2		= &hundred_thousand,

	},

	{

		.procname	= "qos_offline_wait_interval_ms",

		.data		= &sysctl_offline_wait_interval,

		.maxlen		= sizeof(unsigned int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= SYSCTL_ONE_HUNDRED,

		.extra2		= &one_thousand,

	},

#endif

	{}

};
@@ -8303,7 +8334,7 @@ static void unthrottle_qos_cfs_rq(struct cfs_rq *cfs_rq) 
		resched_curr(rq);

}



static int unthrottle_qos_cfs_rqs(int cpu)

static int __unthrottle_qos_cfs_rqs(int cpu)

{

	struct cfs_rq *cfs_rq, *tmp_rq;

	int res = 0;
@@ -8319,8 +8350,22 @@ static int unthrottle_qos_cfs_rqs(int cpu) 
	return res;

}



static int unthrottle_qos_cfs_rqs(int cpu)

{

	int res;



	res = __unthrottle_qos_cfs_rqs(cpu);

	if (res)

		hrtimer_cancel(&(per_cpu(qos_overload_timer, cpu)));



	return res;

}



static bool check_qos_cfs_rq(struct cfs_rq *cfs_rq)

{

	if (unlikely(__this_cpu_read(qos_cpu_overload)))

		return false;



	if (unlikely(cfs_rq && cfs_rq->tg->qos_level < 0 &&

		     !sched_idle_cpu(smp_processor_id()) &&

		     cfs_rq->h_nr_running == cfs_rq->idle_h_nr_running)) {
@@ -8345,6 +8390,74 @@ static inline void unthrottle_qos_sched_group(struct cfs_rq *cfs_rq) 
		unthrottle_qos_cfs_rq(cfs_rq);

	rq_unlock_irqrestore(rq, &rf);

}



void sched_qos_offline_wait(void)

{

	long qos_level;



	while (unlikely(this_cpu_read(qos_cpu_overload))) {

		rcu_read_lock();

		qos_level = task_group(current)->qos_level;

		rcu_read_unlock();

		if (qos_level != -1 || fatal_signal_pending(current))

			break;



		schedule_timeout_killable(msecs_to_jiffies(sysctl_offline_wait_interval));

	}

}



int sched_qos_cpu_overload(void)

{

	return __this_cpu_read(qos_cpu_overload);

}



static enum hrtimer_restart qos_overload_timer_handler(struct hrtimer *timer)

{

	struct rq_flags rf;

	struct rq *rq = this_rq();



	rq_lock_irqsave(rq, &rf);

	if (__unthrottle_qos_cfs_rqs(smp_processor_id()))

		__this_cpu_write(qos_cpu_overload, 1);

	rq_unlock_irqrestore(rq, &rf);



	return HRTIMER_NORESTART;

}



static void start_qos_hrtimer(int cpu)

{

	ktime_t time;

	struct hrtimer *hrtimer = &(per_cpu(qos_overload_timer, cpu));



	time = ktime_add_ms(hrtimer->base->get_time(), (u64)sysctl_overload_detect_period);

	hrtimer_set_expires(hrtimer, time);

	hrtimer_start_expires(hrtimer, HRTIMER_MODE_ABS_PINNED);

}



void init_qos_hrtimer(int cpu)

{

	struct hrtimer *hrtimer = &(per_cpu(qos_overload_timer, cpu));



	hrtimer_init(hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);

	hrtimer->function = qos_overload_timer_handler;

}



/*

 * To avoid Priority inversion issues, when this cpu is qos_cpu_overload,

 * we should schedule offline tasks to run so that they can leave kernel

 * critical sections, and throttle them before returning to user mode.

 */

static void qos_schedule_throttle(struct task_struct *p)

{

	if (unlikely(current->flags & PF_KTHREAD))

		return;



	if (unlikely(this_cpu_read(qos_cpu_overload))) {

		if (is_offline_task(p))

			set_notify_resume(p);

	}

}



#endif



#ifdef CONFIG_SMP
@@ -8507,6 +8620,10 @@ done: __maybe_unused; 
	update_misfit_status(p, rq);

	sched_fair_update_stop_tick(rq, p);



#ifdef CONFIG_QOS_SCHED

	qos_schedule_throttle(p);

#endif



	return p;



idle:
@@ -8531,6 +8648,8 @@ done: __maybe_unused; 
		rq->idle_stamp = 0;

		goto again;

	}



	__this_cpu_write(qos_cpu_overload, 0);

#endif

	/*

	 * rq is about to be idle, check if we need to update the

kernel/sched/sched.h

+4 −0
Original line number Diff line number Diff line
@@ -1411,6 +1411,10 @@ do { \ 
	flags = _raw_spin_rq_lock_irqsave(rq);	\

} while (0)



#ifdef CONFIG_QOS_SCHED

void init_qos_hrtimer(int cpu);

#endif



#ifdef CONFIG_SCHED_SMT

extern void __update_idle_core(struct rq *rq);