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- Do the push of pending hrtimers away from a CPU which is being

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offlined earlier in the offlining process in order to prevent
   a deadlock
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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
This commit is contained in:
Linus Torvalds 2023-11-19 13:35:07 -08:00
commit b0014556a2
4 changed files with 22 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/cpuhotplug.h
View File

@ -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,

4
include/linux/hrtimer.h
View File

@ -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

8
kernel/cpu.c
View File

@ -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] = {

33
kernel/time/hrtimer.c
View File

@ -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;
}