[PATCH] Fix the unnecessary entropy call in the irq handler

Currently add_interrupt_randomness() is called at each interrupt when one
of the handlers has SA_SAMPLE_RANDOM flag, regardless whether the interrupt
is processed by that handler or not.  This results in the higher latency
and perfomance loss.

The patch fixes this behavior to avoid the unnecessary call by checking the
return value from each handler.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/alpha/kernel/irq.c

@@ -83,6 +83,7 @@ handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
 		 struct irqaction *action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
+	int ret;
 
 	do {
 		if (!(action->flags & SA_INTERRUPT))
@@ -90,8 +91,9 @@ handle_IRQ_event(unsigned int irq, struct pt_regs *regs,
 		else
 			local_irq_disable();
 
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/arm/kernel/irq.c

@@ -261,7 +261,7 @@ static int
 __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 {
 	unsigned int status;
-	int retval = 0;
+	int ret, retval = 0;
 
 	spin_unlock(&irq_controller_lock);
 
@@ -270,8 +270,10 @@ __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 
 	status = 0;
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 

arch/arm26/kernel/irq.c

@@ -187,6 +187,7 @@ static void
 __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 {
 	unsigned int status;
+	int ret;
 
 	spin_unlock(&irq_controller_lock);
 	if (!(action->flags & SA_INTERRUPT))
@@ -194,8 +195,9 @@ __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 
 	status = 0;
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 

arch/cris/kernel/irq.c

@@ -125,7 +125,7 @@ asmlinkage void do_IRQ(int irq, struct pt_regs * regs)
 {
 	struct irqaction *action;
 	int do_random, cpu;
-        int retval = 0;
+        int ret, retval = 0;
 
         cpu = smp_processor_id();
         irq_enter();
@@ -137,8 +137,10 @@ asmlinkage void do_IRQ(int irq, struct pt_regs * regs)
                         local_irq_enable();
                 do_random = 0;
                 do {
+			ret = action->handler(irq, action->dev_id, regs);
+			if (ret == IRQ_HANDLED)
 				do_random |= action->flags;
-                        retval |= action->handler(irq, action->dev_id, regs);
+                        retval |= ret;
                         action = action->next;
                 } while (action);
 

arch/i386/kernel/irq.c

@@ -220,14 +220,16 @@ asmlinkage int handle_IRQ_event(unsigned int irq,
 		struct pt_regs *regs, struct irqaction *action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
-	int retval = 0;
+	int ret, retval = 0;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/ia64/kernel/irq.c

@@ -255,14 +255,16 @@ int handle_IRQ_event(unsigned int irq,
 		struct pt_regs *regs, struct irqaction *action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
-	int retval = 0;
+	int ret, retval = 0;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/mips/baget/irq.c

@@ -180,7 +180,7 @@ int get_irq_list(char *buf)
 static void do_IRQ(int irq, struct pt_regs * regs)
 {
 	struct irqaction *action;
-	int do_random, cpu;
+	int ret, do_random, cpu;
 
 	cpu = smp_processor_id();
 	irq_enter();
@@ -194,8 +194,9 @@ static void do_IRQ(int irq, struct pt_regs * regs)
 		action = *(irq + irq_action);
 		do_random = 0;
         	do {
+			ret = action->handler(irq, action->dev_id, regs);
+			if (ret == IRQ_HANDLED)
 				do_random |= action->flags;
-			action->handler(irq, action->dev_id, regs);
 			action = action->next;
         	} while (action);
 		if (do_random & SA_SAMPLE_RANDOM)

arch/mips/kernel/irq.c

@@ -144,14 +144,16 @@ inline void synchronize_irq(unsigned int irq)
 int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
-	int retval = 0;
+	int ret, retval = 0;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/ppc/kernel/irq.c

@@ -414,13 +414,15 @@ static inline void
 handle_irq_event(int irq, struct pt_regs *regs, struct irqaction *action)
 {
 	int status = 0;
+	int ret;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/ppc64/kernel/irq.c

@@ -363,14 +363,16 @@ int show_interrupts(struct seq_file *p, void *v)
 int handle_irq_event(int irq, struct pt_regs *regs, struct irqaction *action)
 {
 	int status = 0;
-	int retval = 0;
+	int ret, retval = 0;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/sh/kernel/irq.c

@@ -137,14 +137,16 @@ int show_interrupts(struct seq_file *p, void *v)
 int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
-	int retval = 0;
+	int ret, retval = 0;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		retval |= action->handler(irq, action->dev_id, regs);
+		retval |= ret;
 		action = action->next;
 	} while (action);
 

arch/sh64/kernel/irq.c

@@ -148,6 +148,7 @@ asmlinkage void do_NMI(unsigned long vector_num, struct pt_regs * regs)
 int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
 {
 	int status;
+	int ret;
 
 	status = 1;	/* Force the "do bottom halves" bit */
 
@@ -155,8 +156,9 @@ int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction *
                 local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/um/kernel/irq.c

@@ -147,13 +147,15 @@ int handle_IRQ_event(unsigned int irq, struct pt_regs * regs,
 		     struct irqaction * action)
 {
 	int status = 1;	/* Force the "do bottom halves" bit */
+	int ret;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/v850/kernel/irq.c

@@ -141,13 +141,15 @@ int show_interrupts(struct seq_file *p, void *v)
 int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
 {
 	int status = 1; /* Force the "do bottom halves" bit */
+	int ret;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)

arch/x86_64/kernel/irq.c

@@ -213,13 +213,15 @@ inline void synchronize_irq(unsigned int irq)
 int handle_IRQ_event(unsigned int irq, struct pt_regs * regs, struct irqaction * action)
 {
 	int status = 1; /* Force the "do bottom halves" bit */
+	int ret;
 
 	if (!(action->flags & SA_INTERRUPT))
 		local_irq_enable();
 
 	do {
+		ret = action->handler(irq, action->dev_id, regs);
+		if (ret == IRQ_HANDLED)
 			status |= action->flags;
-		action->handler(irq, action->dev_id, regs);
 		action = action->next;
 	} while (action);
 	if (status & SA_SAMPLE_RANDOM)