x86/irq: Store irq descriptor in vector array

We can spare the irq_desc lookup in the interrupt entry code if we
store the descriptor pointer in the vector array instead the interrupt
number.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/20150802203609.717724106@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 16 insertions, 21 deletions

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 140950fb9902..e010847583d7 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -211,22 +211,21 @@ u64 arch_irq_stat(void)
 __visible unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
 {
 	struct pt_regs *old_regs = set_irq_regs(regs);
-
+	struct irq_desc * desc;
 	/* high bit used in ret_from_ code  */
 	unsigned vector = ~regs->orig_ax;
-	unsigned irq;
 
 	entering_irq();
 
-	irq = __this_cpu_read(vector_irq[vector]);
+	desc = __this_cpu_read(vector_irq[vector]);
 
-	if (!handle_irq(irq, regs)) {
+	if (!handle_irq(desc, regs)) {
 		ack_APIC_irq();
 
-		if (irq != VECTOR_RETRIGGERED) {
-			pr_emerg_ratelimited("%s: %d.%d No irq handler for vector (irq %d)\n",
+		if (desc != VECTOR_RETRIGGERED) {
+			pr_emerg_ratelimited("%s: %d.%d No irq handler for vector\n",
 					     __func__, smp_processor_id(),
-					     vector, irq);
+					     vector);
 		} else {
 			__this_cpu_write(vector_irq[vector], VECTOR_UNUSED);
 		}
@@ -330,10 +329,10 @@ static struct cpumask affinity_new, online_new;
  */
 int check_irq_vectors_for_cpu_disable(void)
 {
-	int irq, cpu;
 	unsigned int this_cpu, vector, this_count, count;
 	struct irq_desc *desc;
 	struct irq_data *data;
+	int cpu;
 
 	this_cpu = smp_processor_id();
 	cpumask_copy(&online_new, cpu_online_mask);
@@ -341,24 +340,21 @@ int check_irq_vectors_for_cpu_disable(void)
 
 	this_count = 0;
 	for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
-		irq = __this_cpu_read(vector_irq[vector]);
-		if (irq < 0)
-			continue;
-		desc = irq_to_desc(irq);
-		if (!desc)
+		desc = __this_cpu_read(vector_irq[vector]);
+		if (IS_ERR_OR_NULL(desc))
 			continue;
-
 		/*
 		 * Protect against concurrent action removal, affinity
 		 * changes etc.
 		 */
 		raw_spin_lock(&desc->lock);
 		data = irq_desc_get_irq_data(desc);
-		cpumask_copy(&affinity_new, irq_data_get_affinity_mask(data));
+		cpumask_copy(&affinity_new,
+			     irq_data_get_affinity_mask(data));
 		cpumask_clear_cpu(this_cpu, &affinity_new);
 
 		/* Do not count inactive or per-cpu irqs. */
-		if (!irq_has_action(irq) || irqd_is_per_cpu(data)) {
+		if (!irq_desc_has_action(desc) || irqd_is_per_cpu(data)) {
 			raw_spin_unlock(&desc->lock);
 			continue;
 		}
@@ -399,8 +395,8 @@ int check_irq_vectors_for_cpu_disable(void)
 		for (vector = FIRST_EXTERNAL_VECTOR;
 		     vector < first_system_vector; vector++) {
 			if (!test_bit(vector, used_vectors) &&
-			    per_cpu(vector_irq, cpu)[vector] <= VECTOR_UNUSED)
-				count++;
+			    IS_ERR_OR_NULL(per_cpu(vector_irq, cpu)[vector]))
+			    count++;
 		}
 	}
 
@@ -504,14 +500,13 @@ void fixup_irqs(void)
 	for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; vector++) {
 		unsigned int irr;
 
-		if (__this_cpu_read(vector_irq[vector]) <= VECTOR_UNUSED)
+		if (IS_ERR_OR_NULL(__this_cpu_read(vector_irq[vector])))
 			continue;
 
 		irr = apic_read(APIC_IRR + (vector / 32 * 0x10));
 		if (irr  & (1 << (vector % 32))) {
-			irq = __this_cpu_read(vector_irq[vector]);
+			desc = __this_cpu_read(vector_irq[vector]);
 
-			desc = irq_to_desc(irq);
 			raw_spin_lock(&desc->lock);
 			data = irq_desc_get_irq_data(desc);
 			chip = irq_data_get_irq_chip(data);