From: Thomas Gleixner <tglx(a)linutronix.de>
[ Upstream commit 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 ]
2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15(a)huawei.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Liu Tie <liutie4(a)huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
include/linux/cpuhotplug.h | 1 +
include/linux/hrtimer.h | 4 ++--
kernel/cpu.c | 8 +++++++-
kernel/time/hrtimer.c | 33 ++++++++++++---------------------
4 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 71a0a5ffdbb1a..dd9f035be63f7 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -139,6 +139,7 @@ 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,
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 542b4fa2cda9b..3bdaa92a2cab3 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -508,9 +508,9 @@ 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
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c9ca190ec0347..34c09c3d37bc6 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1418,7 +1418,7 @@ 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",
@@ -1485,6 +1485,12 @@ 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] = {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 8512f06f0ebef..bf74f43e42af0 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1922,29 +1922,22 @@ 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],
@@ -1955,15 +1948,13 @@ 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;
}
--
2.42.0
From: Thomas Gleixner <tglx(a)linutronix.de>
[ Upstream commit 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 ]
2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15(a)huawei.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Liu Tie <liutie4(a)huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
include/linux/cpuhotplug.h | 1 +
include/linux/hrtimer.h | 4 ++--
kernel/cpu.c | 8 +++++++-
kernel/time/hrtimer.c | 33 ++++++++++++---------------------
4 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 8134cc3b99cdc..206d7ac411b88 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -141,6 +141,7 @@ 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,
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 48be92aded5ee..16c68a7287bc4 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -526,9 +526,9 @@ 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
diff --git a/kernel/cpu.c b/kernel/cpu.c
index c08456af0c7fe..ba579bb6b8978 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1473,7 +1473,7 @@ 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",
@@ -1540,6 +1540,12 @@ 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] = {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 8e3c9228aec97..e2a055e462551 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2105,29 +2105,22 @@ 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],
@@ -2138,15 +2131,13 @@ 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;
}
--
2.42.0
From: Thomas Gleixner <tglx(a)linutronix.de>
[ Upstream commit 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 ]
2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15(a)huawei.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Liu Tie <liutie4(a)huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
include/linux/cpuhotplug.h | 1 +
include/linux/hrtimer.h | 4 ++--
kernel/cpu.c | 8 +++++++-
kernel/time/hrtimer.c | 33 ++++++++++++---------------------
4 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 7cc2889608e0f..f5a5df3a8cfd1 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -149,6 +149,7 @@ 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,
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 7f1b8549ebcee..a88be8bd4e1d1 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -526,9 +526,9 @@ 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
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 008b50da22246..abf717c4f57c2 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1595,7 +1595,7 @@ 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",
@@ -1662,6 +1662,12 @@ 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] = {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 70deb2f01e97a..ede09dda36e90 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2114,29 +2114,22 @@ 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],
@@ -2147,15 +2140,13 @@ 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;
}
--
2.42.0
From: Thomas Gleixner <tglx(a)linutronix.de>
[ Upstream commit 5c0930ccaad5a74d74e8b18b648c5eb21ed2fe94 ]
2b8272ff4a70 ("cpu/hotplug: Prevent self deadlock on CPU hot-unplug")
solved the straight forward CPU hotplug deadlock vs. the scheduler
bandwidth timer. Yu discovered a more involved variant where a task which
has a bandwidth timer started on the outgoing CPU holds a lock and then
gets throttled. If the lock required by one of the CPU hotplug callbacks
the hotplug operation deadlocks because the unthrottling timer event is not
handled on the dying CPU and can only be recovered once the control CPU
reaches the hotplug state which pulls the pending hrtimers from the dead
CPU.
Solve this by pushing the hrtimers away from the dying CPU in the dying
callbacks. Nothing can queue a hrtimer on the dying CPU at that point because
all other CPUs spin in stop_machine() with interrupts disabled and once the
operation is finished the CPU is marked offline.
Reported-by: Yu Liao <liaoyu15(a)huawei.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Liu Tie <liutie4(a)huawei.com>
Link: https://lore.kernel.org/r/87a5rphara.ffs@tglx
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
include/linux/cpuhotplug.h | 1 +
include/linux/hrtimer.h | 4 ++--
kernel/cpu.c | 8 +++++++-
kernel/time/hrtimer.c | 33 ++++++++++++---------------------
4 files changed, 22 insertions(+), 24 deletions(-)
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index c7156bb56e831..c1ecc843b97d2 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -193,6 +193,7 @@ 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,
diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 0ee140176f102..f2044d5a652b5 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -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
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 393114c10c285..0e786de993e01 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1697,7 +1697,7 @@ 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",
@@ -1764,6 +1764,12 @@ 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] = {
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 97409581e9dac..eebd0f31daa8b 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -2216,29 +2216,22 @@ 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],
@@ -2249,15 +2242,13 @@ 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;
}
--
2.42.0
From: Zhang Rui <rui.zhang(a)intel.com>
[ Upstream commit ec9aedb2aa1ab7ac420c00b31f5edc5be15ec167 ]
Currently, the kernel enumerates the possible CPUs by parsing both ACPI
MADT Local APIC entries and x2APIC entries. So CPUs with "valid" APIC IDs,
even if they have duplicated APIC IDs in Local APIC and x2APIC, are always
enumerated.
Below is what ACPI MADT Local APIC and x2APIC describes on an
Ivebridge-EP system,
[02Ch 0044 1] Subtable Type : 00 [Processor Local APIC]
[02Fh 0047 1] Local Apic ID : 00
...
[164h 0356 1] Subtable Type : 00 [Processor Local APIC]
[167h 0359 1] Local Apic ID : 39
[16Ch 0364 1] Subtable Type : 00 [Processor Local APIC]
[16Fh 0367 1] Local Apic ID : FF
...
[3ECh 1004 1] Subtable Type : 09 [Processor Local x2APIC]
[3F0h 1008 4] Processor x2Apic ID : 00000000
...
[B5Ch 2908 1] Subtable Type : 09 [Processor Local x2APIC]
[B60h 2912 4] Processor x2Apic ID : 00000077
As a result, kernel shows "smpboot: Allowing 168 CPUs, 120 hotplug CPUs".
And this wastes significant amount of memory for the per-cpu data.
Plus this also breaks https://lore.kernel.org/all/87edm36qqb.ffs@tglx/,
because __max_logical_packages is over-estimated by the APIC IDs in
the x2APIC entries.
According to https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#pro…:
"[Compatibility note] On some legacy OSes, Logical processors with APIC
ID values less than 255 (whether in XAPIC or X2APIC mode) must use the
Processor Local APIC structure to convey their APIC information to OSPM,
and those processors must be declared in the DSDT using the Processor()
keyword. Logical processors with APIC ID values 255 and greater must use
the Processor Local x2APIC structure and be declared using the Device()
keyword."
Therefore prevent the registration of x2APIC entries with an APIC ID less
than 255 if the local APIC table enumerates valid APIC IDs.
[ tglx: Simplify the logic ]
Signed-off-by: Zhang Rui <rui.zhang(a)intel.com>
Signed-off-by: Thomas Gleixner <tglx(a)linutronix.de>
Tested-by: Peter Zijlstra <peterz(a)infradead.org>
Link: https://lore.kernel.org/r/20230702162802.344176-1-rui.zhang@intel.com
Signed-off-by: Sasha Levin <sashal(a)kernel.org>
---
arch/x86/kernel/acpi/boot.c | 34 +++++++++++++++-------------------
1 file changed, 15 insertions(+), 19 deletions(-)
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 2252340b2133e..14af7fbdc6b5e 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -62,6 +62,7 @@ int acpi_fix_pin2_polarity __initdata;
#ifdef CONFIG_X86_LOCAL_APIC
static u64 acpi_lapic_addr __initdata = APIC_DEFAULT_PHYS_BASE;
+static bool has_lapic_cpus __initdata;
static bool acpi_support_online_capable;
#endif
@@ -235,6 +236,14 @@ acpi_parse_x2apic(union acpi_subtable_headers *header, const unsigned long end)
if (!acpi_is_processor_usable(processor->lapic_flags))
return 0;
+ /*
+ * According to https://uefi.org/specs/ACPI/6.5/05_ACPI_Software_Programming_Model.html#pro…
+ * when MADT provides both valid LAPIC and x2APIC entries, the APIC ID
+ * in x2APIC must be equal or greater than 0xff.
+ */
+ if (has_lapic_cpus && apic_id < 0xff)
+ return 0;
+
/*
* We need to register disabled CPU as well to permit
* counting disabled CPUs. This allows us to size
@@ -1114,10 +1123,7 @@ static int __init early_acpi_parse_madt_lapic_addr_ovr(void)
static int __init acpi_parse_madt_lapic_entries(void)
{
- int count;
- int x2count = 0;
- int ret;
- struct acpi_subtable_proc madt_proc[2];
+ int count, x2count = 0;
if (!boot_cpu_has(X86_FEATURE_APIC))
return -ENODEV;
@@ -1126,21 +1132,11 @@ static int __init acpi_parse_madt_lapic_entries(void)
acpi_parse_sapic, MAX_LOCAL_APIC);
if (!count) {
- memset(madt_proc, 0, sizeof(madt_proc));
- madt_proc[0].id = ACPI_MADT_TYPE_LOCAL_APIC;
- madt_proc[0].handler = acpi_parse_lapic;
- madt_proc[1].id = ACPI_MADT_TYPE_LOCAL_X2APIC;
- madt_proc[1].handler = acpi_parse_x2apic;
- ret = acpi_table_parse_entries_array(ACPI_SIG_MADT,
- sizeof(struct acpi_table_madt),
- madt_proc, ARRAY_SIZE(madt_proc), MAX_LOCAL_APIC);
- if (ret < 0) {
- pr_err("Error parsing LAPIC/X2APIC entries\n");
- return ret;
- }
-
- count = madt_proc[0].count;
- x2count = madt_proc[1].count;
+ count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
+ acpi_parse_lapic, MAX_LOCAL_APIC);
+ has_lapic_cpus = count > 0;
+ x2count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_X2APIC,
+ acpi_parse_x2apic, MAX_LOCAL_APIC);
}
if (!count && !x2count) {
pr_err("No LAPIC entries present\n");
--
2.42.0