powerpc/smp: Remove migrate_irq() custom implementation

Some powerpc platforms use this to move IRQs away from a CPU being
unplugged. This function has several bugs such as not taking the right
locks or failing to NULL check pointers.

There's a new generic function doing exactly the same thing without all
the bugs, so let's use it instead.

mpe: The obvious place for the select of GENERIC_IRQ_MIGRATION is on
HOTPLUG_CPU, but that doesn't work. On some configs PM_SLEEP_SMP will
select HOTPLUG_CPU even though its dependencies are not met, which means
the select of GENERIC_IRQ_MIGRATION doesn't happen. That leads to the
build breaking. Fix it by moving the select of GENERIC_IRQ_MIGRATION to
SMP.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/smp.h

@@ -62,7 +62,6 @@ extern void smp_generic_take_timebase(void);
 DECLARE_PER_CPU(unsigned int, cpu_pvr);
 
 #ifdef CONFIG_HOTPLUG_CPU
-extern void migrate_irqs(void);
 int generic_cpu_disable(void);
 void generic_cpu_die(unsigned int cpu);
 void generic_set_cpu_dead(unsigned int cpu);

arch/powerpc/kernel/irq.c

@@ -442,46 +442,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
 	return sum;
 }
 
-#ifdef CONFIG_HOTPLUG_CPU
-void migrate_irqs(void)
-{
-	struct irq_desc *desc;
-	unsigned int irq;
-	static int warned;
-	cpumask_var_t mask;
-	const struct cpumask *map = cpu_online_mask;
-
-	alloc_cpumask_var(&mask, GFP_KERNEL);
-
-	for_each_irq_desc(irq, desc) {
-		struct irq_data *data;
-		struct irq_chip *chip;
-
-		data = irq_desc_get_irq_data(desc);
-		if (irqd_is_per_cpu(data))
-			continue;
-
-		chip = irq_data_get_irq_chip(data);
-
-		cpumask_and(mask, irq_data_get_affinity_mask(data), map);
-		if (cpumask_any(mask) >= nr_cpu_ids) {
-			pr_warn("Breaking affinity for irq %i\n", irq);
-			cpumask_copy(mask, map);
-		}
-		if (chip->irq_set_affinity)
-			chip->irq_set_affinity(data, mask, true);
-		else if (desc->action && !(warned++))
-			pr_err("Cannot set affinity for irq %i\n", irq);
-	}
-
-	free_cpumask_var(mask);
-
-	local_irq_enable();
-	mdelay(1);
-	local_irq_disable();
-}
-#endif
-
 static inline void check_stack_overflow(void)
 {
 #ifdef CONFIG_DEBUG_STACKOVERFLOW

arch/powerpc/kernel/smp.c

@@ -439,7 +439,14 @@ int generic_cpu_disable(void)
 #ifdef CONFIG_PPC64
 	vdso_data->processorCount--;
 #endif
-	migrate_irqs();
+	/* Update affinity of all IRQs previously aimed at this CPU */
+	irq_migrate_all_off_this_cpu();
+
+	/* Give the CPU time to drain in-flight ones */
+	local_irq_enable();
+	mdelay(1);
+	local_irq_disable();
+
 	return 0;
 }
 

arch/powerpc/platforms/Kconfig.cputype

@@ -373,6 +373,7 @@ config PPC_PERF_CTRS
 
 config SMP
 	depends on PPC_BOOK3S || PPC_BOOK3E || FSL_BOOKE || PPC_47x
+	select GENERIC_IRQ_MIGRATION
 	bool "Symmetric multi-processing support"
 	---help---
 	  This enables support for systems with more than one CPU. If you have