Kill the busy spinning on the control side and just wait for the hotplugged
cpu to tell that it reached the dead state.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
include/linux/cpu.h | 5 +++--
include/linux/cpuhotplug.h | 1 +
kernel/cpu.c | 16 ++++++++++++----
kernel/sched/idle.c | 5 +----
4 files changed, 17 insertions(+), 10 deletions(-)
Index: b/include/linux/cpu.h
===================================================================
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -276,14 +276,15 @@ void arch_cpu_idle_enter(void);
void arch_cpu_idle_exit(void);
void arch_cpu_idle_dead(void);
-DECLARE_PER_CPU(bool, cpu_dead_idle);
-
int cpu_report_state(int cpu);
int cpu_check_up_prepare(int cpu);
void cpu_set_state_online(int cpu);
#ifdef CONFIG_HOTPLUG_CPU
bool cpu_wait_death(unsigned int cpu, int seconds);
bool cpu_report_death(void);
+void cpuhp_report_idle_dead(void);
+#else
+static inline void cpuhp_report_idle_dead(void) { }
#endif /* #ifdef CONFIG_HOTPLUG_CPU */
#endif /* _LINUX_CPU_H_ */
Index: b/include/linux/cpuhotplug.h
===================================================================
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -6,6 +6,7 @@ enum cpuhp_state {
CPUHP_CREATE_THREADS,
CPUHP_NOTIFY_PREPARE,
CPUHP_BRINGUP_CPU,
+ CPUHP_AP_IDLE_DEAD,
CPUHP_AP_OFFLINE,
CPUHP_AP_NOTIFY_STARTING,
CPUHP_AP_ONLINE,
Index: b/kernel/cpu.c
===================================================================
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -688,6 +688,7 @@ static int take_cpu_down(void *_param)
static int takedown_cpu(unsigned int cpu)
{
+ struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
int err;
/*
@@ -733,10 +734,8 @@ static int takedown_cpu(unsigned int cpu
*
* Wait for the stop thread to go away.
*/
- while (!per_cpu(cpu_dead_idle, cpu))
- cpu_relax();
- smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
- per_cpu(cpu_dead_idle, cpu) = false;
+ wait_for_completion(&st->done);
+ BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
/* Interrupts are moved away from the dying cpu, reenable alloc/free */
irq_unlock_sparse();
@@ -756,6 +755,15 @@ static int notify_dead(unsigned int cpu)
return 0;
}
+void cpuhp_report_idle_dead(void)
+{
+ struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
+
+ BUG_ON(st->state != CPUHP_AP_OFFLINE);
+ st->state = CPUHP_AP_IDLE_DEAD;
+ complete(&st->done);
+}
+
#else
#define notify_down_prepare NULL
#define takedown_cpu NULL
Index: b/kernel/sched/idle.c
===================================================================
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -194,8 +194,6 @@ static void cpuidle_idle_call(void)
rcu_idle_exit();
}
-DEFINE_PER_CPU(bool, cpu_dead_idle);
-
/*
* Generic idle loop implementation
*
@@ -224,8 +222,7 @@ static void cpu_idle_loop(void)
if (cpu_is_offline(smp_processor_id())) {
rcu_cpu_notify(NULL, CPU_DYING_IDLE,
(void *)(long)smp_processor_id());
- smp_mb(); /* all activity before dead. */
- this_cpu_write(cpu_dead_idle, true);
+ cpuhp_report_idle_dead();
arch_cpu_idle_dead();
}
--
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