Commit b0014556 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull timer fix from Borislav Petkov:

 - Do the push of pending hrtimers away from a CPU which is being
   offlined earlier in the offlining process in order to prevent a
   deadlock

* tag 'timers_urgent_for_v6.7_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  hrtimers: Push pending hrtimers away from outgoing CPU earlier
parents 2a0adc49 5c0930cc

include/linux/cpuhotplug.h

+1 −0
Original line number Diff line number Diff line
@@ -195,6 +195,7 @@ enum cpuhp_state { 
	CPUHP_AP_ARM_CORESIGHT_CTI_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
@@ -531,9 +531,9 @@ extern void sysrq_timer_list_show(void); 


int hrtimers_prepare_cpu(unsigned int cpu);

#ifdef CONFIG_HOTPLUG_CPU

int hrtimers_dead_cpu(unsigned int cpu);

int hrtimers_cpu_dying(unsigned int cpu);

#else

#define hrtimers_dead_cpu	NULL

#define hrtimers_cpu_dying	NULL

#endif



#endif

kernel/cpu.c

+7 −1
Original line number Diff line number Diff line
@@ -2113,7 +2113,7 @@ static struct cpuhp_step cpuhp_hp_states[] = { 
	[CPUHP_HRTIMERS_PREPARE] = {

		.name			= "hrtimers:prepare",

		.startup.single		= hrtimers_prepare_cpu,

		.teardown.single	= hrtimers_dead_cpu,

		.teardown.single	= NULL,

	},

	[CPUHP_SMPCFD_PREPARE] = {

		.name			= "smpcfd:prepare",
@@ -2205,6 +2205,12 @@ 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

+12 −21
Original line number Diff line number Diff line
@@ -2219,29 +2219,22 @@ static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base, 
	}

}



int hrtimers_dead_cpu(unsigned int scpu)

int hrtimers_cpu_dying(unsigned int dying_cpu)

{

	struct hrtimer_cpu_base *old_base, *new_base;

	int i;

	int i, ncpu = cpumask_first(cpu_active_mask);



	BUG_ON(cpu_online(scpu));

	tick_cancel_sched_timer(scpu);

	tick_cancel_sched_timer(dying_cpu);



	old_base = this_cpu_ptr(&hrtimer_bases);

	new_base = &per_cpu(hrtimer_bases, ncpu);



	/*

	 * 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(&new_base->lock);

	raw_spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);

	raw_spin_lock(&old_base->lock);

	raw_spin_lock_nested(&new_base->lock, SINGLE_DEPTH_NESTING);



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

		migrate_hrtimer_list(&old_base->clock_base[i],
@@ -2252,15 +2245,13 @@ int hrtimers_dead_cpu(unsigned int scpu) 
	 * The migration might have changed the first expiring softirq

	 * timer on this CPU. Update it.

	 */

	hrtimer_update_softirq_timer(new_base, false);

	__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);



	raw_spin_unlock(&old_base->lock);

	raw_spin_unlock(&new_base->lock);

	raw_spin_unlock(&old_base->lock);



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

	__hrtimer_peek_ahead_timers();

	local_irq_enable();

	local_bh_enable();

	return 0;

}