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)

10 files changed, 18 insertions, 18 deletions

diff --git a/drivers/net/tulip/de2104x.c b/drivers/net/tulip/de2104x.c
index e1b48bd86646..2cfd9634895a 100644
--- a/drivers/net/tulip/de2104x.c
+++ b/drivers/net/tulip/de2104x.c
@@ -484,7 +484,7 @@ rx_next:
 	de->rx_tail = rx_tail;
 }
 
-static irqreturn_t de_interrupt (int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t de_interrupt (int irq, void *dev_instance)
 {
 	struct net_device *dev = dev_instance;
 	struct de_private *de = dev->priv;
diff --git a/drivers/net/tulip/de4x5.c b/drivers/net/tulip/de4x5.c
index fb5fa7d68888..e17f9779ead2 100644
--- a/drivers/net/tulip/de4x5.c
+++ b/drivers/net/tulip/de4x5.c
@@ -896,7 +896,7 @@ static struct {
 */
 static int     de4x5_open(struct net_device *dev);
 static int     de4x5_queue_pkt(struct sk_buff *skb, struct net_device *dev);
-static irqreturn_t de4x5_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t de4x5_interrupt(int irq, void *dev_id);
 static int     de4x5_close(struct net_device *dev);
 static struct  net_device_stats *de4x5_get_stats(struct net_device *dev);
 static void    de4x5_local_stats(struct net_device *dev, char *buf, int pkt_len);
@@ -1538,7 +1538,7 @@ de4x5_queue_pkt(struct sk_buff *skb, struct net_device *dev)
 ** interrupt is asserted and this routine entered.
 */
 static irqreturn_t
-de4x5_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+de4x5_interrupt(int irq, void *dev_id)
 {
     struct net_device *dev = (struct net_device *)dev_id;
     struct de4x5_private *lp;
diff --git a/drivers/net/tulip/dmfe.c b/drivers/net/tulip/dmfe.c
index ccf2c225f084..4dd8a0bae860 100644
--- a/drivers/net/tulip/dmfe.c
+++ b/drivers/net/tulip/dmfe.c
@@ -300,7 +300,7 @@ static struct net_device_stats * dmfe_get_stats(struct DEVICE *);
 static void dmfe_set_filter_mode(struct DEVICE *);
 static const struct ethtool_ops netdev_ethtool_ops;
 static u16 read_srom_word(long ,int);
-static irqreturn_t dmfe_interrupt(int , void *, struct pt_regs *);
+static irqreturn_t dmfe_interrupt(int , void *);
 #ifdef CONFIG_NET_POLL_CONTROLLER
 static void poll_dmfe (struct net_device *dev);
 #endif
@@ -735,7 +735,7 @@ static int dmfe_stop(struct DEVICE *dev)
  *	receive the packet to upper layer, free the transmitted packet
  */
 
-static irqreturn_t dmfe_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t dmfe_interrupt(int irq, void *dev_id)
 {
 	struct DEVICE *dev = dev_id;
 	struct dmfe_board_info *db = netdev_priv(dev);
@@ -806,7 +806,7 @@ static void poll_dmfe (struct net_device *dev)
 	/* disable_irq here is not very nice, but with the lockless
 	   interrupt handler we have no other choice. */
 	disable_irq(dev->irq);
-	dmfe_interrupt (dev->irq, dev, NULL);
+	dmfe_interrupt (dev->irq, dev);
 	enable_irq(dev->irq);
 }
 #endif
diff --git a/drivers/net/tulip/interrupt.c b/drivers/net/tulip/interrupt.c
index 7f8f5d42a761..e3488d7b8ede 100644
--- a/drivers/net/tulip/interrupt.c
+++ b/drivers/net/tulip/interrupt.c
@@ -496,7 +496,7 @@ static inline unsigned int phy_interrupt (struct net_device *dev)
 
 /* The interrupt handler does all of the Rx thread work and cleans up
    after the Tx thread. */
-irqreturn_t tulip_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
+irqreturn_t tulip_interrupt(int irq, void *dev_instance)
 {
 	struct net_device *dev = (struct net_device *)dev_instance;
 	struct tulip_private *tp = netdev_priv(dev);
diff --git a/drivers/net/tulip/tulip.h b/drivers/net/tulip/tulip.h
index 25668ddb1f7e..ad107f45c7b1 100644
--- a/drivers/net/tulip/tulip.h
+++ b/drivers/net/tulip/tulip.h
@@ -424,7 +424,7 @@ int tulip_read_eeprom(struct net_device *dev, int location, int addr_len);
 /* interrupt.c */
 extern unsigned int tulip_max_interrupt_work;
 extern int tulip_rx_copybreak;
-irqreturn_t tulip_interrupt(int irq, void *dev_instance, struct pt_regs *regs);
+irqreturn_t tulip_interrupt(int irq, void *dev_instance);
 int tulip_refill_rx(struct net_device *dev);
 #ifdef CONFIG_TULIP_NAPI
 int tulip_poll(struct net_device *dev, int *budget);
diff --git a/drivers/net/tulip/tulip_core.c b/drivers/net/tulip/tulip_core.c
index 831919a81918..0aee618f883c 100644
--- a/drivers/net/tulip/tulip_core.c
+++ b/drivers/net/tulip/tulip_core.c
@@ -1823,7 +1823,7 @@ static void poll_tulip (struct net_device *dev)
 	/* disable_irq here is not very nice, but with the lockless
 	   interrupt handler we have no other choice. */
 	disable_irq(dev->irq);
-	tulip_interrupt (dev->irq, dev, NULL);
+	tulip_interrupt (dev->irq, dev);
 	enable_irq(dev->irq);
 }
 #endif
diff --git a/drivers/net/tulip/uli526x.c b/drivers/net/tulip/uli526x.c
index 0b176be51eb3..229158e8e4be 100644
--- a/drivers/net/tulip/uli526x.c
+++ b/drivers/net/tulip/uli526x.c
@@ -224,7 +224,7 @@ static struct net_device_stats * uli526x_get_stats(struct net_device *);
 static void uli526x_set_filter_mode(struct net_device *);
 static const struct ethtool_ops netdev_ethtool_ops;
 static u16 read_srom_word(long, int);
-static irqreturn_t uli526x_interrupt(int, void *, struct pt_regs *);
+static irqreturn_t uli526x_interrupt(int, void *);
 static void uli526x_descriptor_init(struct uli526x_board_info *, unsigned long);
 static void allocate_rx_buffer(struct uli526x_board_info *);
 static void update_cr6(u32, unsigned long);
@@ -659,7 +659,7 @@ static int uli526x_stop(struct net_device *dev)
  *	receive the packet to upper layer, free the transmitted packet
  */
 
-static irqreturn_t uli526x_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t uli526x_interrupt(int irq, void *dev_id)
 {
 	struct net_device *dev = dev_id;
 	struct uli526x_board_info *db = netdev_priv(dev);
diff --git a/drivers/net/tulip/winbond-840.c b/drivers/net/tulip/winbond-840.c
index 2fca1ee24f5a..002a05e0722f 100644
--- a/drivers/net/tulip/winbond-840.c
+++ b/drivers/net/tulip/winbond-840.c
@@ -332,7 +332,7 @@ static void tx_timeout(struct net_device *dev);
 static int alloc_ringdesc(struct net_device *dev);
 static void free_ringdesc(struct netdev_private *np);
 static int  start_tx(struct sk_buff *skb, struct net_device *dev);
-static irqreturn_t intr_handler(int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t intr_handler(int irq, void *dev_instance);
 static void netdev_error(struct net_device *dev, int intr_status);
 static int  netdev_rx(struct net_device *dev);
 static u32 __set_rx_mode(struct net_device *dev);
@@ -1110,7 +1110,7 @@ static void netdev_tx_done(struct net_device *dev)
 
 /* The interrupt handler does all of the Rx thread work and cleans up
    after the Tx thread. */
-static irqreturn_t intr_handler(int irq, void *dev_instance, struct pt_regs *rgs)
+static irqreturn_t intr_handler(int irq, void *dev_instance)
 {
 	struct net_device *dev = (struct net_device *)dev_instance;
 	struct netdev_private *np = netdev_priv(dev);
diff --git a/drivers/net/tulip/xircom_cb.c b/drivers/net/tulip/xircom_cb.c
index 629eac645289..61d313049dd0 100644
--- a/drivers/net/tulip/xircom_cb.c
+++ b/drivers/net/tulip/xircom_cb.c
@@ -114,7 +114,7 @@ struct xircom_private {
 /* Function prototypes */
 static int xircom_probe(struct pci_dev *pdev, const struct pci_device_id *id);
 static void xircom_remove(struct pci_dev *pdev);
-static irqreturn_t xircom_interrupt(int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t xircom_interrupt(int irq, void *dev_instance);
 static int xircom_start_xmit(struct sk_buff *skb, struct net_device *dev);
 static int xircom_open(struct net_device *dev);
 static int xircom_close(struct net_device *dev);
@@ -334,7 +334,7 @@ static void __devexit xircom_remove(struct pci_dev *pdev)
 	leave("xircom_remove");
 }
 
-static irqreturn_t xircom_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t xircom_interrupt(int irq, void *dev_instance)
 {
 	struct net_device *dev = (struct net_device *) dev_instance;
 	struct xircom_private *card = netdev_priv(dev);
@@ -513,7 +513,7 @@ static struct net_device_stats *xircom_get_stats(struct net_device *dev)
 static void xircom_poll_controller(struct net_device *dev)
 {
 	disable_irq(dev->irq);
-	xircom_interrupt(dev->irq, dev, NULL);
+	xircom_interrupt(dev->irq, dev);
 	enable_irq(dev->irq);
 }
 #endif
diff --git a/drivers/net/tulip/xircom_tulip_cb.c b/drivers/net/tulip/xircom_tulip_cb.c
index 312788caa4c6..a998c5d0ae9c 100644
--- a/drivers/net/tulip/xircom_tulip_cb.c
+++ b/drivers/net/tulip/xircom_tulip_cb.c
@@ -328,7 +328,7 @@ static void xircom_init_ring(struct net_device *dev);
 static int xircom_start_xmit(struct sk_buff *skb, struct net_device *dev);
 static int xircom_rx(struct net_device *dev);
 static void xircom_media_change(struct net_device *dev);
-static irqreturn_t xircom_interrupt(int irq, void *dev_instance, struct pt_regs *regs);
+static irqreturn_t xircom_interrupt(int irq, void *dev_instance);
 static int xircom_close(struct net_device *dev);
 static struct net_device_stats *xircom_get_stats(struct net_device *dev);
 static int xircom_ioctl(struct net_device *dev, struct ifreq *rq, int cmd);
@@ -1044,7 +1044,7 @@ static void check_duplex(struct net_device *dev)
 
 /* The interrupt handler does all of the Rx thread work and cleans up
    after the Tx thread. */
-static irqreturn_t xircom_interrupt(int irq, void *dev_instance, struct pt_regs *regs)
+static irqreturn_t xircom_interrupt(int irq, void *dev_instance)
 {
 	struct net_device *dev = dev_instance;
 	struct xircom_private *tp = netdev_priv(dev);