Commit 2701a7bb authored by Zhang Qiao's avatar Zhang Qiao Committed by Yongqiang Liu
Browse files

sched: Throttle offline task at tracehook_notify_resume() 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4VZJT


CVE: NA

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

Before, when detect the cpu is overloaded, we throttle offline
tasks at exit_to_user_mode_loop() before returning to user mode.
Some architects(e.g.,arm64) do not support QOS scheduler because
a task do not via exit_to_user_mode_loop() return to userspace at
these platforms.
In order to slove this problem and support qos scheduler on all
architectures, if we require throttling offline tasks, we set flag
TIF_NOTIFY_RESUME to an offline task when it is picked and throttle
it at tracehook_notify_resume().

Signed-off-by: default avatarZhang Qiao <zhangqiao22@huawei.com>
Reviewed-by: default avatarChen Hui <judy.chenhui@huawei.com>
Signed-off-by: default avatarYongqiang Liu <liuyongqiang13@huawei.com>
parent 70d21cfa

arch/x86/entry/common.c

+1 −6
Original line number Diff line number Diff line
@@ -162,10 +162,6 @@ static void exit_to_usermode_loop(struct pt_regs *regs, u32 cached_flags) 
		if (cached_flags & _TIF_SIGPENDING)

			do_signal(regs);



#ifdef CONFIG_QOS_SCHED

		sched_qos_offline_wait();

#endif



		if (cached_flags & _TIF_NOTIFY_RESUME) {

			clear_thread_flag(TIF_NOTIFY_RESUME);

			tracehook_notify_resume(regs);
@@ -198,8 +194,7 @@ __visible inline void prepare_exit_to_usermode(struct pt_regs *regs) 


	cached_flags = READ_ONCE(ti->flags);



	if (unlikely((cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS) ||

		     sched_qos_cpu_overload()))

	if (unlikely(cached_flags & EXIT_TO_USERMODE_LOOP_FLAGS))

		exit_to_usermode_loop(regs, cached_flags);



#ifdef CONFIG_COMPAT

include/linux/tracehook.h

+4 −0
Original line number Diff line number Diff line
@@ -194,6 +194,10 @@ static inline void tracehook_notify_resume(struct pt_regs *regs) 


	mem_cgroup_handle_over_high();

	blkcg_maybe_throttle_current();

#ifdef CONFIG_QOS_SCHED

	sched_qos_offline_wait();

#endif



}



#endif	/* <linux/tracehook.h> */

kernel/sched/fair.c

+27 −7
Original line number Diff line number Diff line
@@ -26,6 +26,7 @@ 
#endif

#ifdef CONFIG_QOS_SCHED

#include <linux/delay.h>

#include <linux/tracehook.h>

#endif

#include <trace/events/sched.h>
@@ -7029,20 +7030,18 @@ static bool check_qos_cfs_rq(struct cfs_rq *cfs_rq) 
void sched_qos_offline_wait(void)

{

	long qos_level;

	unsigned long wait_interval;



	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 || signal_pending(current))

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

			break;

		msleep_interruptible(sysctl_offline_wait_interval);

	}

}



int sched_qos_cpu_overload(void)

{

	return __this_cpu_read(qos_cpu_overload);

		wait_interval = msecs_to_jiffies(sysctl_offline_wait_interval);

		schedule_timeout_killable(wait_interval);

	}

}



static enum hrtimer_restart qos_overload_timer_handler(struct hrtimer *timer)
@@ -7075,6 +7074,23 @@ void init_qos_hrtimer(int 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 (task_group(p)->qos_level < 0)

			set_notify_resume(p);

	}

}



#endif



static struct task_struct *
@@ -7202,6 +7218,10 @@ done: __maybe_unused; 
	if (hrtick_enabled(rq))

		hrtick_start_fair(rq, p);



#ifdef CONFIG_QOS_SCHED

	qos_schedule_throttle(p);

#endif



	return p;



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