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Subject[patch V2 59/67] smp: Convert core to hotplug state machine
From: Richard Weinberger <richard@nod.at>

Install the callbacks via the state machine. They are installed at runtime so
smpcfd_prepare_cpu() needs to be invoked by the boot-CPU.

Signed-off-by: Richard Weinberger <richard@nod.at>
[ Added the dropped CPU dying case back in. ]
Signed-off-by: Richard Cochran <rcochran@linutronix.de>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Davidlohr Bueso <dave@stgolabs>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
---
include/linux/cpuhotplug.h | 2 +
include/linux/smp.h | 5 ++
kernel/cpu.c | 9 +++++
kernel/smp.c | 79 ++++++++++++++++++---------------------------
4 files changed, 48 insertions(+), 47 deletions(-)

--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -19,6 +19,7 @@ enum cpuhp_state {
CPUHP_HRTIMERS_PREPARE,
CPUHP_PROFILE_PREPARE,
CPUHP_X2APIC_PREPARE,
+ CPUHP_SMPCFD_PREPARE,
CPUHP_TIMERS_DEAD,
CPUHP_NOTIFY_PREPARE,
CPUHP_BRINGUP_CPU,
@@ -58,6 +59,7 @@ enum cpuhp_state {
CPUHP_AP_ARM_CORESIGHT4_STARTING,
CPUHP_AP_ARM64_ISNDEP_STARTING,
CPUHP_AP_LEDTRIG_STARTING,
+ CPUHP_AP_SMPCFD_DYING,
CPUHP_AP_X86_TBOOT_DYING,
CPUHP_AP_NOTIFY_STARTING,
CPUHP_AP_ONLINE,
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -196,4 +196,9 @@ extern void arch_enable_nonboot_cpus_end

void smp_setup_processor_id(void);

+/* SMP core functions */
+int smpcfd_prepare_cpu(unsigned int cpu);
+int smpcfd_dead_cpu(unsigned int cpu);
+int smpcfd_dying_cpu(unsigned int cpu);
+
#endif /* __LINUX_SMP_H */
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1195,6 +1195,11 @@ static struct cpuhp_step cpuhp_bp_states
.startup = hrtimers_prepare_cpu,
.teardown = hrtimers_dead_cpu,
},
+ [CPUHP_SMPCFD_PREPARE] = {
+ .name = "SMPCFD prepare",
+ .startup = smpcfd_prepare_cpu,
+ .teardown = smpcfd_dead_cpu,
+ },
[CPUHP_TIMERS_DEAD] = {
.name = "timers dead",
.startup = NULL,
@@ -1218,6 +1223,10 @@ static struct cpuhp_step cpuhp_bp_states
.teardown = NULL,
.cant_stop = true,
},
+ [CPUHP_AP_SMPCFD_DYING] = {
+ .startup = NULL,
+ .teardown = smpcfd_dying_cpu,
+ },
/*
* Handled on controll processor until the plugged processor manages
* this itself.
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -33,69 +33,54 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(str

static void flush_smp_call_function_queue(bool warn_cpu_offline);

-static int
-hotplug_cfd(struct notifier_block *nfb, unsigned long action, void *hcpu)
+int smpcfd_prepare_cpu(unsigned int cpu)
{
- long cpu = (long)hcpu;
struct call_function_data *cfd = &per_cpu(cfd_data, cpu);

- switch (action) {
- case CPU_UP_PREPARE:
- case CPU_UP_PREPARE_FROZEN:
- if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
- cpu_to_node(cpu)))
- return notifier_from_errno(-ENOMEM);
- cfd->csd = alloc_percpu(struct call_single_data);
- if (!cfd->csd) {
- free_cpumask_var(cfd->cpumask);
- return notifier_from_errno(-ENOMEM);
- }
- break;
-
-#ifdef CONFIG_HOTPLUG_CPU
- case CPU_UP_CANCELED:
- case CPU_UP_CANCELED_FROZEN:
- /* Fall-through to the CPU_DEAD[_FROZEN] case. */
-
- case CPU_DEAD:
- case CPU_DEAD_FROZEN:
+ if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL,
+ cpu_to_node(cpu)))
+ return -ENOMEM;
+ cfd->csd = alloc_percpu(struct call_single_data);
+ if (!cfd->csd) {
free_cpumask_var(cfd->cpumask);
- free_percpu(cfd->csd);
- break;
+ return -ENOMEM;
+ }

- case CPU_DYING:
- case CPU_DYING_FROZEN:
- /*
- * The IPIs for the smp-call-function callbacks queued by other
- * CPUs might arrive late, either due to hardware latencies or
- * because this CPU disabled interrupts (inside stop-machine)
- * before the IPIs were sent. So flush out any pending callbacks
- * explicitly (without waiting for the IPIs to arrive), to
- * ensure that the outgoing CPU doesn't go offline with work
- * still pending.
- */
- flush_smp_call_function_queue(false);
- break;
-#endif
- };
+ return 0;
+}

- return NOTIFY_OK;
+int smpcfd_dead_cpu(unsigned int cpu)
+{
+ struct call_function_data *cfd = &per_cpu(cfd_data, cpu);
+
+ free_cpumask_var(cfd->cpumask);
+ free_percpu(cfd->csd);
+ return 0;
}

-static struct notifier_block hotplug_cfd_notifier = {
- .notifier_call = hotplug_cfd,
-};
+int smpcfd_dying_cpu(unsigned int cpu)
+{
+ /*
+ * The IPIs for the smp-call-function callbacks queued by other
+ * CPUs might arrive late, either due to hardware latencies or
+ * because this CPU disabled interrupts (inside stop-machine)
+ * before the IPIs were sent. So flush out any pending callbacks
+ * explicitly (without waiting for the IPIs to arrive), to
+ * ensure that the outgoing CPU doesn't go offline with work
+ * still pending.
+ */
+ flush_smp_call_function_queue(false);
+ return 0;
+}

void __init call_function_init(void)
{
- void *cpu = (void *)(long)smp_processor_id();
int i;

for_each_possible_cpu(i)
init_llist_head(&per_cpu(call_single_queue, i));

- hotplug_cfd(&hotplug_cfd_notifier, CPU_UP_PREPARE, cpu);
- register_cpu_notifier(&hotplug_cfd_notifier);
+ smpcfd_prepare_cpu(smp_processor_id());
}

/*

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