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>

diff --git a/arch/parisc/include/asm/processor.h b/arch/parisc/include/asm/processor.h
index 00636421279549b1a2ba3a1896a536b452ba8470..4621ceb51314702a066b241bc6c8a36ec6e5b261 100644 (file)
--- a/arch/parisc/include/asm/processor.h
+++ b/arch/parisc/include/asm/processor.h
@@ -95,6 +95,7 @@ struct cpuinfo_parisc {
 
 extern struct system_cpuinfo_parisc boot_cpu_data;
 DECLARE_PER_CPU(struct cpuinfo_parisc, cpu_data);
+extern int time_keeper_id;             /* CPU used for timekeeping */
 
 #define CPU_HVERSION ((boot_cpu_data.hversion >> 4) & 0x0FFF)
 

diff --git a/arch/parisc/kernel/smp.c b/arch/parisc/kernel/smp.c
index 8c5ea457b6e12195019fb2062a7dec1875b752d5..24d0744c3b3abcaf72b7fdab3defc201c4be1c7e 100644 (file)
--- 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();

diff --git a/arch/parisc/kernel/time.c b/arch/parisc/kernel/time.c
index 874b128c5783b442827c555ab789d86198c4e03c..bb27dfeeddfcc2f776c70ccf0a84df3c8971da09 100644 (file)
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -40,6 +40,8 @@
 
 #include <linux/timex.h>
 
+int time_keeper_id __read_mostly;      /* CPU used for timekeeping. */
+
 static unsigned long clocktick __ro_after_init;        /* timer cycles per tick */
 
 /*
@@ -84,7 +86,7 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
        cpuinfo->it_value = next_tick;
 
        /* Go do system house keeping. */
-       if (cpu != 0)
+       if (IS_ENABLED(CONFIG_SMP) && (cpu != time_keeper_id))
                ticks_elapsed = 0;
        legacy_timer_tick(ticks_elapsed);