Commit 12e9b566 authored by Yu Liao's avatar Yu Liao
Browse files

Revert "hrtimers: Push pending hrtimers away from outgoing CPU earlier" 

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8OSNK


CVE: NA

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

Commit 4cf0b18c("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
introduce the following issue:
- CPU1 goes offline and all hrtimers are migrated to other CPUs
- CPU1 continues the offline process and migrates all tasks. In some
 case, hrtimer_start will be called to restart cfs_period_timer
- CPU1 shuts down and does not handle timers, task throttled by CFS
  bandwidth never get scheduled.

So revert it before we provide a better solution.

This reverts commit 4cf0b18c.

Signed-off-by: default avatarYu Liao <liaoyu15@huawei.com>
parent 93510cd4

include/linux/cpuhotplug.h

+0 −1
Original line number Diff line number Diff line
@@ -137,7 +137,6 @@ enum cpuhp_state { 
	CPUHP_AP_ARM_CORESIGHT_STARTING,

	CPUHP_AP_ARM64_ISNDEP_STARTING,

	CPUHP_AP_SMPCFD_DYING,

	CPUHP_AP_HRTIMERS_DYING,

	CPUHP_AP_X86_TBOOT_DYING,

	CPUHP_AP_ARM_CACHE_B15_RAC_DYING,

	CPUHP_AP_ONLINE,

include/linux/hrtimer.h

+2 −2
Original line number Diff line number Diff line
@@ -508,9 +508,9 @@ extern void sysrq_timer_list_show(void); 


int hrtimers_prepare_cpu(unsigned int cpu);

#ifdef CONFIG_HOTPLUG_CPU

int hrtimers_cpu_dying(unsigned int cpu);

int hrtimers_dead_cpu(unsigned int cpu);

#else

#define hrtimers_cpu_dying	NULL

#define hrtimers_dead_cpu	NULL

#endif



#endif

kernel/cpu.c

+1 −7
Original line number Diff line number Diff line
@@ -1390,7 +1390,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { 
	[CPUHP_HRTIMERS_PREPARE] = {

		.name			= "hrtimers:prepare",

		.startup.single		= hrtimers_prepare_cpu,

		.teardown.single	= NULL,

		.teardown.single	= hrtimers_dead_cpu,

	},

	[CPUHP_SMPCFD_PREPARE] = {

		.name			= "smpcfd:prepare",
@@ -1457,12 +1457,6 @@ static struct cpuhp_step cpuhp_hp_states[] = { 
		.startup.single		= NULL,

		.teardown.single	= smpcfd_dying_cpu,

	},

	[CPUHP_AP_HRTIMERS_DYING] = {

		.name			= "hrtimers:dying",

		.startup.single		= NULL,

		.teardown.single	= hrtimers_cpu_dying,

	},



	/* Entry state on starting. Interrupts enabled from here on. Transient

	 * state for synchronsization */

	[CPUHP_AP_ONLINE] = {

kernel/time/hrtimer.c

+21 −12
Original line number Diff line number Diff line
@@ -1922,22 +1922,29 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base, 
	}

}



int hrtimers_cpu_dying(unsigned int dying_cpu)

int hrtimers_dead_cpu(unsigned int scpu)

{

	struct hrtimer_cpu_base *old_base, *new_base;

	int i, ncpu = cpumask_first(cpu_active_mask);



	tick_cancel_sched_timer(dying_cpu);

	int i;



	old_base = this_cpu_ptr(&hrtimer_bases);

	new_base = &per_cpu(hrtimer_bases, ncpu);

	BUG_ON(cpu_online(scpu));

	tick_cancel_sched_timer(scpu);



	/*

	 * this BH disable ensures that raise_softirq_irqoff() does

	 * not wakeup ksoftirqd (and acquire the pi-lock) while

	 * holding the cpu_base lock

	 */

	local_bh_disable();

	local_irq_disable();

	old_base = &per_cpu(hrtimer_bases, scpu);

	new_base = this_cpu_ptr(&hrtimer_bases);

	/*

	 * The caller is globally serialized and nobody else

	 * takes two locks at once, deadlock is not possible.

	 */

	raw_spin_lock(&old_base->lock);

	raw_spin_lock_nested(&new_base->lock, SINGLE_DEPTH_NESTING);

	raw_spin_lock(&new_base->lock);

	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);



	for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {

		migrate_hrtimer_list(&old_base->clock_base[i],
@@ -1948,13 +1955,15 @@ int hrtimers_cpu_dying(unsigned int dying_cpu) 
	 * The migration might have changed the first expiring softirq

	 * timer on this CPU. Update it.

	 */

	__hrtimer_get_next_event(new_base, HRTIMER_ACTIVE_SOFT);

	/* Tell the other CPU to retrigger the next event */

	smp_call_function_single(ncpu, retrigger_next_event, NULL, 0);

	hrtimer_update_softirq_timer(new_base, false);



	raw_spin_unlock(&new_base->lock);

	raw_spin_unlock(&old_base->lock);

	raw_spin_unlock(&new_base->lock);



	/* Check, if we got expired work to do */

	__hrtimer_peek_ahead_timers();

	local_irq_enable();

	local_bh_enable();

	return 0;

}