IRQ: Maintain regs pointer globally rather than passing to IRQ handlers

Maintain a per-CPU global "struct pt_regs *" variable which can be used instead
of passing regs around manually through all ~1800 interrupt handlers in the
Linux kernel.

The regs pointer is used in few places, but it potentially costs both stack
space and code to pass it around.  On the FRV arch, removing the regs parameter
from all the genirq function results in a 20% speed up of the IRQ exit path
(ie: from leaving timer_interrupt() to leaving do_IRQ()).

Where appropriate, an arch may override the generic storage facility and do
something different with the variable.  On FRV, for instance, the address is
maintained in GR28 at all times inside the kernel as part of general exception
handling.

Having looked over the code, it appears that the parameter may be handed down
through up to twenty or so layers of functions.  Consider a USB character
device attached to a USB hub, attached to a USB controller that posts its
interrupts through a cascaded auxiliary interrupt controller.  A character
device driver may want to pass regs to the sysrq handler through the input
layer which adds another few layers of parameter passing.

I've build this code with allyesconfig for x86_64 and i386.  I've runtested the
main part of the code on FRV and i386, though I can't test most of the drivers.
I've also done partial conversion for powerpc and MIPS - these at least compile
with minimal configurations.

This will affect all archs.  Mostly the changes should be relatively easy.
Take do_IRQ(), store the regs pointer at the beginning, saving the old one:

	struct pt_regs *old_regs = set_irq_regs(regs);

And put the old one back at the end:

	set_irq_regs(old_regs);

Don't pass regs through to generic_handle_irq() or __do_IRQ().

In timer_interrupt(), this sort of change will be necessary:

	-	update_process_times(user_mode(regs));
	-	profile_tick(CPU_PROFILING, regs);
	+	update_process_times(user_mode(get_irq_regs()));
	+	profile_tick(CPU_PROFILING);

I'd like to move update_process_times()'s use of get_irq_regs() into itself,
except that i386, alone of the archs, uses something other than user_mode().

Some notes on the interrupt handling in the drivers:

 (*) input_dev() is now gone entirely.  The regs pointer is no longer stored in
     the input_dev struct.

 (*) finish_unlinks() in drivers/usb/host/ohci-q.c needs checking.  It does
     something different depending on whether it's been supplied with a regs
     pointer or not.

 (*) Various IRQ handler function pointers have been moved to type
     irq_handler_t.

Signed-Off-By: David Howells <dhowells@redhat.com>
(cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit)

9 files changed, 27 insertions, 35 deletions

diff --git a/arch/powerpc/platforms/cell/interrupt.c b/arch/powerpc/platforms/cell/interrupt.c
index 8533f13a5ed1..434fb934dd20 100644
--- a/arch/powerpc/platforms/cell/interrupt.c
+++ b/arch/powerpc/platforms/cell/interrupt.c
@@ -190,11 +190,11 @@ struct irq_host *iic_get_irq_host(int node)
 EXPORT_SYMBOL_GPL(iic_get_irq_host);
 
 
-static irqreturn_t iic_ipi_action(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t iic_ipi_action(int irq, void *dev_id)
 {
 	int ipi = (int)(long)dev_id;
 
-	smp_message_recv(ipi, regs);
+	smp_message_recv(ipi);
 
 	return IRQ_HANDLED;
 }
diff --git a/arch/powerpc/platforms/cell/spider-pic.c b/arch/powerpc/platforms/cell/spider-pic.c
index b0e95d594c51..21a9ebd4978e 100644
--- a/arch/powerpc/platforms/cell/spider-pic.c
+++ b/arch/powerpc/platforms/cell/spider-pic.c
@@ -213,8 +213,7 @@ static struct irq_host_ops spider_host_ops = {
 	.xlate = spider_host_xlate,
 };
 
-static void spider_irq_cascade(unsigned int irq, struct irq_desc *desc,
-			       struct pt_regs *regs)
+static void spider_irq_cascade(unsigned int irq, struct irq_desc *desc)
 {
 	struct spider_pic *pic = desc->handler_data;
 	unsigned int cs, virq;
@@ -225,7 +224,7 @@ static void spider_irq_cascade(unsigned int irq, struct irq_desc *desc,
 	else
 		virq = irq_linear_revmap(pic->host, cs);
 	if (virq != NO_IRQ)
-		generic_handle_irq(virq, regs);
+		generic_handle_irq(virq);
 	desc->chip->eoi(irq);
 }
 
diff --git a/arch/powerpc/platforms/powermac/low_i2c.c b/arch/powerpc/platforms/powermac/low_i2c.c
index c2c7cf75dd5f..bfc4829162f1 100644
--- a/arch/powerpc/platforms/powermac/low_i2c.c
+++ b/arch/powerpc/platforms/powermac/low_i2c.c
@@ -342,7 +342,7 @@ static void kw_i2c_handle_interrupt(struct pmac_i2c_host_kw *host, u8 isr)
 }
 
 /* Interrupt handler */
-static irqreturn_t kw_i2c_irq(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t kw_i2c_irq(int irq, void *dev_id)
 {
 	struct pmac_i2c_host_kw *host = dev_id;
 	unsigned long flags;
diff --git a/arch/powerpc/platforms/powermac/pfunc_base.c b/arch/powerpc/platforms/powermac/pfunc_base.c
index ee3b223ab17a..5c6c15c5f9a3 100644
--- a/arch/powerpc/platforms/powermac/pfunc_base.c
+++ b/arch/powerpc/platforms/powermac/pfunc_base.c
@@ -15,7 +15,7 @@
 #define DBG(fmt...)
 #endif
 
-static irqreturn_t macio_gpio_irq(int irq, void *data, struct pt_regs *regs)
+static irqreturn_t macio_gpio_irq(int irq, void *data)
 {
 	pmf_do_irq(data);
 
diff --git a/arch/powerpc/platforms/powermac/pic.c b/arch/powerpc/platforms/powermac/pic.c
index 39f7ddb554ea..e93a115961aa 100644
--- a/arch/powerpc/platforms/powermac/pic.c
+++ b/arch/powerpc/platforms/powermac/pic.c
@@ -440,14 +440,13 @@ static void __init pmac_pic_probe_oldstyle(void)
 }
 #endif /* CONFIG_PPC32 */
 
-static void pmac_u3_cascade(unsigned int irq, struct irq_desc *desc,
-			    struct pt_regs *regs)
+static void pmac_u3_cascade(unsigned int irq, struct irq_desc *desc)
 {
 	struct mpic *mpic = desc->handler_data;
 
-	unsigned int cascade_irq = mpic_get_one_irq(mpic, regs);
+	unsigned int cascade_irq = mpic_get_one_irq(mpic, get_irq_regs());
 	if (cascade_irq != NO_IRQ)
-		generic_handle_irq(cascade_irq, regs);
+		generic_handle_irq(cascade_irq);
 	desc->chip->eoi(irq);
 }
 
diff --git a/arch/powerpc/platforms/pseries/ras.c b/arch/powerpc/platforms/pseries/ras.c
index 311ed1993fc0..b1d3d161249e 100644
--- a/arch/powerpc/platforms/pseries/ras.c
+++ b/arch/powerpc/platforms/pseries/ras.c
@@ -65,16 +65,14 @@ static int ras_check_exception_token;
 #define EPOW_SENSOR_INDEX	0
 #define RAS_VECTOR_OFFSET	0x500
 
-static irqreturn_t ras_epow_interrupt(int irq, void *dev_id,
-					struct pt_regs * regs);
-static irqreturn_t ras_error_interrupt(int irq, void *dev_id,
-					struct pt_regs * regs);
+static irqreturn_t ras_epow_interrupt(int irq, void *dev_id);
+static irqreturn_t ras_error_interrupt(int irq, void *dev_id);
 
 /* #define DEBUG */
 
 
 static void request_ras_irqs(struct device_node *np,
-			irqreturn_t (*handler)(int, void *, struct pt_regs *),
+			irq_handler_t handler,
 			const char *name)
 {
 	int i, index, count = 0;
@@ -166,8 +164,7 @@ __initcall(init_ras_IRQ);
  * to examine the type of power failure and take appropriate action where
  * the time horizon permits something useful to be done.
  */
-static irqreturn_t
-ras_epow_interrupt(int irq, void *dev_id, struct pt_regs * regs)
+static irqreturn_t ras_epow_interrupt(int irq, void *dev_id)
 {
 	int status = 0xdeadbeef;
 	int state = 0;
@@ -210,8 +207,7 @@ ras_epow_interrupt(int irq, void *dev_id, struct pt_regs * regs)
  * For nonrecoverable errors, an error is logged and we stop all processing
  * as quickly as possible in order to prevent propagation of the failure.
  */
-static irqreturn_t
-ras_error_interrupt(int irq, void *dev_id, struct pt_regs * regs)
+static irqreturn_t ras_error_interrupt(int irq, void *dev_id)
 {
 	struct rtas_error_log *rtas_elog;
 	int status = 0xdeadbeef;
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index f82b13e531a3..ad9aec2c6fee 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -121,12 +121,11 @@ static void __init fwnmi_init(void)
 		fwnmi_active = 1;
 }
 
-void pseries_8259_cascade(unsigned int irq, struct irq_desc *desc,
-			  struct pt_regs *regs)
+void pseries_8259_cascade(unsigned int irq, struct irq_desc *desc)
 {
-	unsigned int cascade_irq = i8259_irq(regs);
+	unsigned int cascade_irq = i8259_irq(get_irq_regs());
 	if (cascade_irq != NO_IRQ)
-		generic_handle_irq(cascade_irq, regs);
+		generic_handle_irq(cascade_irq);
 	desc->chip->eoi(irq);
 }
 
diff --git a/arch/powerpc/platforms/pseries/xics.c b/arch/powerpc/platforms/pseries/xics.c
index 253972e5479f..f6bd2f285153 100644
--- a/arch/powerpc/platforms/pseries/xics.c
+++ b/arch/powerpc/platforms/pseries/xics.c
@@ -324,7 +324,7 @@ static unsigned int xics_get_irq_lpar(struct pt_regs *regs)
 
 #ifdef CONFIG_SMP
 
-static irqreturn_t xics_ipi_dispatch(int cpu, struct pt_regs *regs)
+static irqreturn_t xics_ipi_dispatch(int cpu)
 {
 	WARN_ON(cpu_is_offline(cpu));
 
@@ -332,47 +332,47 @@ static irqreturn_t xics_ipi_dispatch(int cpu, struct pt_regs *regs)
 		if (test_and_clear_bit(PPC_MSG_CALL_FUNCTION,
 				       &xics_ipi_message[cpu].value)) {
 			mb();
-			smp_message_recv(PPC_MSG_CALL_FUNCTION, regs);
+			smp_message_recv(PPC_MSG_CALL_FUNCTION);
 		}
 		if (test_and_clear_bit(PPC_MSG_RESCHEDULE,
 				       &xics_ipi_message[cpu].value)) {
 			mb();
-			smp_message_recv(PPC_MSG_RESCHEDULE, regs);
+			smp_message_recv(PPC_MSG_RESCHEDULE);
 		}
 #if 0
 		if (test_and_clear_bit(PPC_MSG_MIGRATE_TASK,
 				       &xics_ipi_message[cpu].value)) {
 			mb();
-			smp_message_recv(PPC_MSG_MIGRATE_TASK, regs);
+			smp_message_recv(PPC_MSG_MIGRATE_TASK);
 		}
 #endif
 #if defined(CONFIG_DEBUGGER) || defined(CONFIG_KEXEC)
 		if (test_and_clear_bit(PPC_MSG_DEBUGGER_BREAK,
 				       &xics_ipi_message[cpu].value)) {
 			mb();
-			smp_message_recv(PPC_MSG_DEBUGGER_BREAK, regs);
+			smp_message_recv(PPC_MSG_DEBUGGER_BREAK);
 		}
 #endif
 	}
 	return IRQ_HANDLED;
 }
 
-static irqreturn_t xics_ipi_action_direct(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t xics_ipi_action_direct(int irq, void *dev_id)
 {
 	int cpu = smp_processor_id();
 
 	direct_qirr_info(cpu, 0xff);
 
-	return xics_ipi_dispatch(cpu, regs);
+	return xics_ipi_dispatch(cpu);
 }
 
-static irqreturn_t xics_ipi_action_lpar(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t xics_ipi_action_lpar(int irq, void *dev_id)
 {
 	int cpu = smp_processor_id();
 
 	lpar_qirr_info(cpu, 0xff);
 
-	return xics_ipi_dispatch(cpu, regs);
+	return xics_ipi_dispatch(cpu);
 }
 
 void xics_cause_IPI(int cpu)
diff --git a/arch/powerpc/platforms/pseries/xics.h b/arch/powerpc/platforms/pseries/xics.h
index 6ee1055b0ffb..db0ec3ba3ae2 100644
--- a/arch/powerpc/platforms/pseries/xics.h
+++ b/arch/powerpc/platforms/pseries/xics.h
@@ -31,7 +31,6 @@ struct xics_ipi_struct {
 extern struct xics_ipi_struct xics_ipi_message[NR_CPUS] __cacheline_aligned;
 
 struct irq_desc;
-extern void pseries_8259_cascade(unsigned int irq, struct irq_desc *desc,
-				 struct pt_regs *regs);
+extern void pseries_8259_cascade(unsigned int irq, struct irq_desc *desc);
 
 #endif /* _POWERPC_KERNEL_XICS_H */