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Subject[PATCH 2/3] cpumask: Introduce DYING mask
Introduce a cpumask that indicates (for each CPU) what direction the
CPU hotplug is currently going. Notably, it tracks rollbacks. Eg. when
an up fails and we do a roll-back down, it will accurately reflect the
direction.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
include/linux/cpumask.h | 20 ++++++++++++++++++++
kernel/cpu.c | 6 ++++++
2 files changed, 26 insertions(+)

--- a/include/linux/cpumask.h
+++ b/include/linux/cpumask.h
@@ -91,10 +91,12 @@ extern struct cpumask __cpu_possible_mas
extern struct cpumask __cpu_online_mask;
extern struct cpumask __cpu_present_mask;
extern struct cpumask __cpu_active_mask;
+extern struct cpumask __cpu_dying_mask;
#define cpu_possible_mask ((const struct cpumask *)&__cpu_possible_mask)
#define cpu_online_mask ((const struct cpumask *)&__cpu_online_mask)
#define cpu_present_mask ((const struct cpumask *)&__cpu_present_mask)
#define cpu_active_mask ((const struct cpumask *)&__cpu_active_mask)
+#define cpu_dying_mask ((const struct cpumask *)&__cpu_dying_mask)

extern atomic_t __num_online_cpus;

@@ -826,6 +828,14 @@ set_cpu_active(unsigned int cpu, bool ac
cpumask_clear_cpu(cpu, &__cpu_active_mask);
}

+static 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);
+}

/**
* to_cpumask - convert an NR_CPUS bitmap to a struct cpumask *
@@ -900,6 +910,11 @@ static inline bool cpu_active(unsigned i
return cpumask_test_cpu(cpu, cpu_active_mask);
}

+static inline bool cpu_dying(unsigned int cpu)
+{
+ return cpumask_test_cpu(cpu, cpu_dying_mask);
+}
+
#else

#define num_online_cpus() 1U
@@ -927,6 +942,11 @@ static inline bool cpu_active(unsigned i
return cpu == 0;
}

+static inline bool cpu_dying(unsigned int cpu)
+{
+ return false;
+}
+
#endif /* NR_CPUS > 1 */

#define cpu_is_offline(cpu) unlikely(!cpu_online(cpu))
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -160,6 +160,9 @@ static int cpuhp_invoke_callback(unsigne
int (*cb)(unsigned int cpu);
int ret, cnt;

+ if (bringup != !cpu_dying(cpu))
+ set_cpu_dying(cpu, !bringup);
+
if (st->fail == state) {
st->fail = CPUHP_INVALID;
return -EAGAIN;
@@ -2512,6 +2515,9 @@ EXPORT_SYMBOL(__cpu_present_mask);
struct cpumask __cpu_active_mask __read_mostly;
EXPORT_SYMBOL(__cpu_active_mask);

+struct cpumask __cpu_dying_mask __read_mostly;
+EXPORT_SYMBOL(__cpu_dying_mask);
+
atomic_t __num_online_cpus __read_mostly;
EXPORT_SYMBOL(__num_online_cpus);


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