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)

8 files changed, 14 insertions, 14 deletions

diff --git a/drivers/bluetooth/bcm203x.c b/drivers/bluetooth/bcm203x.c
index 13ba729cdd5..67cdda43f22 100644
--- a/drivers/bluetooth/bcm203x.c
+++ b/drivers/bluetooth/bcm203x.c
@@ -82,7 +82,7 @@ struct bcm203x_data {
         unsigned int            fw_sent;
 };
 
-static void bcm203x_complete(struct urb *urb, struct pt_regs *regs)
+static void bcm203x_complete(struct urb *urb)
 {
         struct bcm203x_data *data = urb->context;
         struct usb_device *udev = urb->dev;
diff --git a/drivers/bluetooth/bfusb.c b/drivers/bluetooth/bfusb.c
index efcc28ec9d9..31ade991aa9 100644
--- a/drivers/bluetooth/bfusb.c
+++ b/drivers/bluetooth/bfusb.c
@@ -95,8 +95,8 @@ struct bfusb_data_scb {
         struct urb *urb;
 };
 
-static void bfusb_tx_complete(struct urb *urb, struct pt_regs *regs);
-static void bfusb_rx_complete(struct urb *urb, struct pt_regs *regs);
+static void bfusb_tx_complete(struct urb *urb);
+static void bfusb_rx_complete(struct urb *urb);
 
 static struct urb *bfusb_get_completed(struct bfusb_data *data)
 {
@@ -190,7 +190,7 @@ static void bfusb_tx_wakeup(struct bfusb_data *data)
         clear_bit(BFUSB_TX_PROCESS, &data->state);
 }
 
-static void bfusb_tx_complete(struct urb *urb, struct pt_regs *regs)
+static void bfusb_tx_complete(struct urb *urb)
 {
         struct sk_buff *skb = (struct sk_buff *) urb->context;
         struct bfusb_data *data = (struct bfusb_data *) skb->dev;
@@ -349,7 +349,7 @@ static inline int bfusb_recv_block(struct bfusb_data *data, int hdr, unsigned ch
         return 0;
 }
 
-static void bfusb_rx_complete(struct urb *urb, struct pt_regs *regs)
+static void bfusb_rx_complete(struct urb *urb)
 {
         struct sk_buff *skb = (struct sk_buff *) urb->context;
         struct bfusb_data *data = (struct bfusb_data *) skb->dev;
diff --git a/drivers/bluetooth/bluecard_cs.c b/drivers/bluetooth/bluecard_cs.c
index 8eebf9ca378..845b8680032 100644
--- a/drivers/bluetooth/bluecard_cs.c
+++ b/drivers/bluetooth/bluecard_cs.c
@@ -497,7 +497,7 @@ static void bluecard_receive(bluecard_info_t *info, unsigned int offset)
 }
 
 
-static irqreturn_t bluecard_interrupt(int irq, void *dev_inst, struct pt_regs *regs)
+static irqreturn_t bluecard_interrupt(int irq, void *dev_inst)
 {
         bluecard_info_t *info = dev_inst;
         unsigned int iobase;
diff --git a/drivers/bluetooth/bpa10x.c b/drivers/bluetooth/bpa10x.c
index e0231dc2cb1..9fca6513562 100644
--- a/drivers/bluetooth/bpa10x.c
+++ b/drivers/bluetooth/bpa10x.c
@@ -263,7 +263,7 @@ static void bpa10x_wakeup(struct bpa10x_data *data)
         }
 }
 
-static void bpa10x_complete(struct urb *urb, struct pt_regs *regs)
+static void bpa10x_complete(struct urb *urb)
 {
         struct bpa10x_data *data = urb->context;
         unsigned char *buf = urb->transfer_buffer;
diff --git a/drivers/bluetooth/bt3c_cs.c b/drivers/bluetooth/bt3c_cs.c
index df7bb016df4..3a96a0babc6 100644
--- a/drivers/bluetooth/bt3c_cs.c
+++ b/drivers/bluetooth/bt3c_cs.c
@@ -338,7 +338,7 @@ static void bt3c_receive(bt3c_info_t *info)
 }
 
 
-static irqreturn_t bt3c_interrupt(int irq, void *dev_inst, struct pt_regs *regs)
+static irqreturn_t bt3c_interrupt(int irq, void *dev_inst)
 {
         bt3c_info_t *info = dev_inst;
         unsigned int iobase;
diff --git a/drivers/bluetooth/btuart_cs.c b/drivers/bluetooth/btuart_cs.c
index 746ccca97f6..3b29086b7c3 100644
--- a/drivers/bluetooth/btuart_cs.c
+++ b/drivers/bluetooth/btuart_cs.c
@@ -288,7 +288,7 @@ static void btuart_receive(btuart_info_t *info)
 }
 
 
-static irqreturn_t btuart_interrupt(int irq, void *dev_inst, struct pt_regs *regs)
+static irqreturn_t btuart_interrupt(int irq, void *dev_inst)
 {
         btuart_info_t *info = dev_inst;
         unsigned int iobase;
diff --git a/drivers/bluetooth/dtl1_cs.c b/drivers/bluetooth/dtl1_cs.c
index 0e99def8a1e..e7c800f4c3a 100644
--- a/drivers/bluetooth/dtl1_cs.c
+++ b/drivers/bluetooth/dtl1_cs.c
@@ -291,7 +291,7 @@ static void dtl1_receive(dtl1_info_t *info)
 }
 
 
-static irqreturn_t dtl1_interrupt(int irq, void *dev_inst, struct pt_regs *regs)
+static irqreturn_t dtl1_interrupt(int irq, void *dev_inst)
 {
         dtl1_info_t *info = dev_inst;
         unsigned int iobase;
diff --git a/drivers/bluetooth/hci_usb.c b/drivers/bluetooth/hci_usb.c
index 0801af4ad2b..7565642a007 100644
--- a/drivers/bluetooth/hci_usb.c
+++ b/drivers/bluetooth/hci_usb.c
@@ -176,8 +176,8 @@ static struct _urb *_urb_dequeue(struct _urb_queue *q)
         return _urb;
 }
 
-static void hci_usb_rx_complete(struct urb *urb, struct pt_regs *regs);
-static void hci_usb_tx_complete(struct urb *urb, struct pt_regs *regs);
+static void hci_usb_rx_complete(struct urb *urb);
+static void hci_usb_tx_complete(struct urb *urb);
 
 #define __pending_tx(husb, type)  (&husb->pending_tx[type-1])
 #define __pending_q(husb, type)   (&husb->pending_q[type-1])
@@ -732,7 +732,7 @@ static inline int __recv_frame(struct hci_usb *husb, int type, void *data, int c
         return 0;
 }
 
-static void hci_usb_rx_complete(struct urb *urb, struct pt_regs *regs)
+static void hci_usb_rx_complete(struct urb *urb)
 {
         struct _urb *_urb = container_of(urb, struct _urb, urb);
         struct hci_usb *husb = (void *) urb->context;
@@ -786,7 +786,7 @@ unlock:
         read_unlock(&husb->completion_lock);
 }
 
-static void hci_usb_tx_complete(struct urb *urb, struct pt_regs *regs)
+static void hci_usb_tx_complete(struct urb *urb)
 {
         struct _urb *_urb = container_of(urb, struct _urb, urb);
         struct hci_usb *husb = (void *) urb->context;