x86/irq: Move IS_ERR_OR_NULL() check into common do_IRQ() code

Both the 64bit and the 32bit handle_irq() implementation check the irq
descriptor pointer with IS_ERR_OR_NULL() and return failure. That can be
done simpler in the common do_IRQ() code.

This reduces the 64bit handle_irq() function to a wrapper around
generic_handle_irq_desc(). Invoke it directly from do_IRQ() to spare the
extra function call.

[ tglx: Got rid of the #ifdef and massaged changelog ]
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/2ec758c7-9aaa-73ab-f083-cc44c86aa741@gmail.com

arch/x86/include/asm/irq.h

@@ -34,7 +34,7 @@ extern __visible void smp_kvm_posted_intr_nested_ipi(struct pt_regs *regs);
 extern void (*x86_platform_ipi_callback)(void);
 extern void native_init_IRQ(void);
 
-extern bool handle_irq(struct irq_desc *desc, struct pt_regs *regs);
+extern void handle_irq(struct irq_desc *desc, struct pt_regs *regs);
 
 extern __visible unsigned int do_IRQ(struct pt_regs *regs);
 

arch/x86/kernel/irq.c

@@ -243,8 +243,12 @@ __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
 	RCU_LOCKDEP_WARN(!rcu_is_watching(), "IRQ failed to wake up RCU");
 
 	desc = __this_cpu_read(vector_irq[vector]);
-
-	if (!handle_irq(desc, regs)) {
+	if (likely(!IS_ERR_OR_NULL(desc))) {
+		if (IS_ENABLED(CONFIG_X86_32))
+			handle_irq(desc, regs);
+		else
+			generic_handle_irq_desc(desc);
+	} else {
 		ack_APIC_irq();
 
 		if (desc != VECTOR_RETRIGGERED && desc != VECTOR_SHUTDOWN) {

arch/x86/kernel/irq_32.c

@@ -148,18 +148,13 @@ void do_softirq_own_stack(void)
 	call_on_stack(__do_softirq, isp);
 }
 
-bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
+void handle_irq(struct irq_desc *desc, struct pt_regs *regs)
 {
 	int overflow = check_stack_overflow();
 
-	if (IS_ERR_OR_NULL(desc))
-		return false;
-
 	if (user_mode(regs) || !execute_on_irq_stack(overflow, desc)) {
 		if (unlikely(overflow))
 			print_stack_overflow();
 		generic_handle_irq_desc(desc);
 	}
-
-	return true;
 }

arch/x86/kernel/irq_64.c

@@ -26,15 +26,6 @@
 DEFINE_PER_CPU_PAGE_ALIGNED(struct irq_stack, irq_stack_backing_store) __visible;
 DECLARE_INIT_PER_CPU(irq_stack_backing_store);
 
-bool handle_irq(struct irq_desc *desc, struct pt_regs *regs)
-{
-	if (IS_ERR_OR_NULL(desc))
-		return false;
-
-	generic_handle_irq_desc(desc);
-	return true;
-}
-
 #ifdef CONFIG_VMAP_STACK
 /*
  * VMAP the backing store with guard pages