From: Ye Bin <yebin10@xxxxxxxxxx>
Introduce '__num_dying_cpus' variable to cache the number of dying CPUs
in the core and just return the cached variable.
Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
---
include/linux/cpumask.h | 20 ++++++++++++++++----
kernel/cpu.c | 2 ++
2 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h
index 2a61ddcf8321..8127fd598f51 100644
--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -135,6 +135,8 @@ extern struct cpumask __cpu_dying_mask;
extern atomic_t __num_online_cpus;
+extern atomic_t __num_dying_cpus;
+
extern cpumask_t cpus_booted_once_mask;
static __always_inline void cpu_max_bits_warn(unsigned int cpu, unsigned int bits)
@@ -1018,10 +1020,14 @@ set_cpu_active(unsigned int cpu, bool active)
static __always_inline void
set_cpu_dying(unsigned int cpu, bool dying)
{
- if (dying)
- cpumask_set_cpu(cpu, &__cpu_dying_mask);
- else
- cpumask_clear_cpu(cpu, &__cpu_dying_mask);
+ if (dying) {
+ if (!cpumask_test_and_set_cpu(cpu, &__cpu_dying_mask))
+ atomic_inc(&__num_dying_cpus);
+ }
+ else {
+ if (cpumask_test_and_clear_cpu(cpu, &__cpu_dying_mask))
+ atomic_dec(&__num_dying_cpus);
+ }
}
/**
@@ -1073,6 +1079,11 @@ static __always_inline unsigned int num_online_cpus(void)
{
return arch_atomic_read(&__num_online_cpus);
}
+
+static __always_inline unsigned int num_dying_cpus(void)
+{
+ return arch_atomic_read(&__num_dying_cpus);
+}
#define num_possible_cpus() cpumask_weight(cpu_possible_mask)
#define num_present_cpus() cpumask_weight(cpu_present_mask)
#define num_active_cpus() cpumask_weight(cpu_active_mask)
@@ -1108,6 +1119,7 @@ static __always_inline bool cpu_dying(unsigned int cpu)
#define num_possible_cpus() 1U
#define num_present_cpus() 1U
#define num_active_cpus() 1U
+#define num_dying_cpus() 0U
static __always_inline bool cpu_online(unsigned int cpu)
{
diff --git a/kernel/cpu.c b/kernel/cpu.c
index f4a2c5845bcb..1c96c04cb259 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2662,6 +2662,8 @@ EXPORT_SYMBOL(__cpu_dying_mask);
atomic_t __num_online_cpus __read_mostly;
EXPORT_SYMBOL(__num_online_cpus);
+atomic_t __num_dying_cpus __read_mostly;
+
void init_cpu_present(const struct cpumask *src)
{
cpumask_copy(&__cpu_present_mask, src);
--
2.31.1
