From 88b3aac6228baaac6a3bcc0808845083b9d9f08f Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@gmx.de>
Date: Fri, 25 Mar 2022 14:31:08 +0100
Subject: parisc: Implement __cpu_die() and __cpu_disable() for CPU hotplugging
Add relevant code to __cpu_die() and __cpu_disable() to finally enable
the CPU hotplugging features. Reset the irq count values in smp_callin()
to zero before bringing up the CPU.
It seems that the firmware may need up to 8 seconds to fully stop a CPU
in which no other PDC calls are allowed to be made. Use a timeout
__cpu_die() to accommodate for this.
Use "chcpu -d 1" to bring CPU1 down, and "chcpu -e 1" to bring it up.
Signed-off-by: Helge Deller <deller@gmx.de>
---
arch/parisc/kernel/smp.c | 102 ++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 87 insertions(+), 15 deletions(-)
(limited to 'arch/parisc/kernel/smp.c')
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index a32a882a2d58..8c5ea457b6e1 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -30,6 +30,7 @@
#include <linux/ftrace.h>
#include <linux/cpu.h>
#include <linux/kgdb.h>
+#include <linux/sched/hotplug.h>
#include <linux/atomic.h>
#include <asm/current.h>
@@ -60,8 +61,6 @@ volatile struct task_struct *smp_init_current_idle_task;
/* track which CPU is booting */
static volatile int cpu_now_booting;
-static int parisc_max_cpus = 1;
-
static DEFINE_PER_CPU(spinlock_t, ipi_lock);
enum ipi_message_type {
@@ -269,7 +268,7 @@ void arch_send_call_function_single_ipi(int cpu)
/*
* Called by secondaries to update state and initialize CPU registers.
*/
-static void __init
+static void
smp_cpu_init(int cpunum)
{
extern void init_IRQ(void); /* arch/parisc/kernel/irq.c */
@@ -309,7 +308,7 @@ smp_cpu_init(int cpunum)
* Slaves start using C here. Indirectly called from smp_slave_stext.
* Do what start_kernel() and main() do for boot strap processor (aka monarch)
*/
-void __init smp_callin(unsigned long pdce_proc)
+void smp_callin(unsigned long pdce_proc)
{
int slave_id = cpu_now_booting;
@@ -334,11 +333,28 @@ void __init smp_callin(unsigned long pdce_proc)
/*
* Bring one cpu online.
*/
-int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
+static int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
{
const struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpuid);
long timeout;
+#ifdef CONFIG_HOTPLUG_CPU
+ int i;
+
+ /* reset irq statistics for this CPU */
+ memset(&per_cpu(irq_stat, cpuid), 0, sizeof(irq_cpustat_t));
+ for (i = 0; i < NR_IRQS; i++) {
+ struct irq_desc *desc = irq_to_desc(i);
+
+ if (desc && desc->kstat_irqs)
+ *per_cpu_ptr(desc->kstat_irqs, cpuid) = 0;
+ }
+#endif
+
+ /* wait until last booting CPU has started. */
+ while (cpu_now_booting)
+ ;
+
/* Let _start know what logical CPU we're booting
** (offset into init_tasks[],cpu_data[])
*/
@@ -374,7 +390,6 @@ int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
if(cpu_online(cpuid)) {
/* Which implies Slave has started up */
cpu_now_booting = 0;
- smp_init_current_idle_task = NULL;
goto alive ;
}
udelay(100);
@@ -415,25 +430,82 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
spin_lock_init(&per_cpu(ipi_lock, cpu));
init_cpu_present(cpumask_of(0));
-
- parisc_max_cpus = max_cpus;
- if (!max_cpus)
- printk(KERN_INFO "SMP mode deactivated.\n");
}
-void smp_cpus_done(unsigned int cpu_max)
+void __init smp_cpus_done(unsigned int cpu_max)
{
- return;
}
int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
- if (cpu != 0 && cpu < parisc_max_cpus && smp_boot_one_cpu(cpu, tidle))
- return -ENOSYS;
+ if (cpu_online(cpu))
+ return 0;
+
+ if (num_online_cpus() < setup_max_cpus && smp_boot_one_cpu(cpu, tidle))
+ return -EIO;
+
+ return cpu_online(cpu) ? 0 : -EIO;
+}
+
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpu_disable(void)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+ unsigned int cpu = smp_processor_id();
+
+ remove_cpu_topology(cpu);
+
+ /*
+ * Take this CPU offline. Once we clear this, we can't return,
+ * and we must not schedule until we're ready to give up the cpu.
+ */
+ set_cpu_online(cpu, false);
+
+ disable_percpu_irq(IPI_IRQ);
+
+ irq_migrate_all_off_this_cpu();
+
+ flush_cache_all_local();
+ flush_tlb_all_local(NULL);
+
+ /* disable all irqs, including timer irq */
+ local_irq_disable();
+
+ /* wait for next timer irq ... */
+ mdelay(1000/HZ+100);
+
+ /* ... and then clear all pending external irqs */
+ set_eiem(0);
+ mtctl(~0UL, CR_EIRR);
+ mfctl(CR_EIRR);
+ mtctl(0, CR_EIRR);
+#endif
+ return 0;
+}
+
+/*
+ * called on the thread which is asking for a CPU to be shutdown -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpu_die(unsigned int cpu)
+{
+ pdc_cpu_rendezvous_lock();
+
+ if (!cpu_wait_death(cpu, 5)) {
+ pr_crit("CPU%u: cpu didn't die\n", cpu);
+ return;
+ }
+ pr_info("CPU%u: is shutting down\n", cpu);
+
+ /* set task's state to interruptible sleep */
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_timeout((IS_ENABLED(CONFIG_64BIT) ? 8:2) * HZ);
- return cpu_online(cpu) ? 0 : -ENOSYS;
+ pdc_cpu_rendezvous_unlock();
}
#ifdef CONFIG_PROC_FS
--
cgit v1.2.3
From 1afde47d082c92c4fd3d9b322d944f8d87469834 Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@gmx.de>
Date: Sun, 27 Mar 2022 15:03:53 +0200
Subject: parisc: Find a new timesync master if current CPU is removed
When CPU hotplugging is enabled, the user may want to remove the
current CPU which is providing the timer ticks. If this happens
we need to find a new timesync master.
Signed-off-by: Helge Deller <deller@gmx.de>
---
arch/parisc/kernel/smp.c | 6 ++++++
1 file changed, 6 insertions(+)
(limited to 'arch/parisc/kernel/smp.c')
diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index 8c5ea457b6e1..24d0744c3b3a 100644
--- a/arch/parisc/kernel/smp.c
+++ b/arch/parisc/kernel/smp.c
@@ -465,6 +465,12 @@ int __cpu_disable(void)
*/
set_cpu_online(cpu, false);
+ /* Find a new timesync master */
+ if (cpu == time_keeper_id) {
+ time_keeper_id = cpumask_first(cpu_online_mask);
+ pr_info("CPU %d is now promoted to time-keeper master\n", time_keeper_id);
+ }
+
disable_percpu_irq(IPI_IRQ);
irq_migrate_all_off_this_cpu();
--
cgit v1.2.3