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)

11 files changed, 14 insertions, 18 deletions

diff --git a/drivers/atm/ambassador.c b/drivers/atm/ambassador.c
index da599e6e9d34..8ff5c4e50823 100644
--- a/drivers/atm/ambassador.c
+++ b/drivers/atm/ambassador.c
@@ -861,10 +861,8 @@ static inline void interrupts_off (amb_dev * dev) {
 
 /********** interrupt handling **********/
 
-static irqreturn_t interrupt_handler(int irq, void *dev_id,
-					struct pt_regs *pt_regs) {
+static irqreturn_t interrupt_handler(int irq, void *dev_id) {
   amb_dev * dev = (amb_dev *) dev_id;
-  (void) pt_regs;
   
   PRINTD (DBG_IRQ|DBG_FLOW, "interrupt_handler: %p", dev_id);
   
diff --git a/drivers/atm/eni.c b/drivers/atm/eni.c
index df359a6c14f6..bc1b13c8f5d7 100644
--- a/drivers/atm/eni.c
+++ b/drivers/atm/eni.c
@@ -1488,7 +1488,7 @@ static void bug_int(struct atm_dev *dev,unsigned long reason)
 }
 
 
-static irqreturn_t eni_int(int irq,void *dev_id,struct pt_regs *regs)
+static irqreturn_t eni_int(int irq,void *dev_id)
 {
 	struct atm_dev *dev;
 	struct eni_dev *eni_dev;
diff --git a/drivers/atm/firestream.c b/drivers/atm/firestream.c
index 5f25e5efefcd..40ab9b65fae9 100644
--- a/drivers/atm/firestream.c
+++ b/drivers/atm/firestream.c
@@ -1546,7 +1546,7 @@ static void __devexit free_freepool (struct fs_dev *dev, struct freepool *fp)
 
 
 
-static irqreturn_t fs_irq (int irq, void *dev_id,  struct pt_regs * pt_regs) 
+static irqreturn_t fs_irq (int irq, void *dev_id) 
 {
 	int i;
 	u32 status;
diff --git a/drivers/atm/fore200e.c b/drivers/atm/fore200e.c
index 98622130de5b..3a7b21ff30a5 100644
--- a/drivers/atm/fore200e.c
+++ b/drivers/atm/fore200e.c
@@ -1328,7 +1328,7 @@ fore200e_irq(struct fore200e* fore200e)
 
 
 static irqreturn_t
-fore200e_interrupt(int irq, void* dev, struct pt_regs* regs)
+fore200e_interrupt(int irq, void* dev)
 {
     struct fore200e* fore200e = FORE200E_DEV((struct atm_dev*)dev);
 
diff --git a/drivers/atm/he.c b/drivers/atm/he.c
index b22a9142b240..c7314a79da0f 100644
--- a/drivers/atm/he.c
+++ b/drivers/atm/he.c
@@ -109,7 +109,7 @@ static int he_open(struct atm_vcc *vcc);
 static void he_close(struct atm_vcc *vcc);
 static int he_send(struct atm_vcc *vcc, struct sk_buff *skb);
 static int he_ioctl(struct atm_dev *dev, unsigned int cmd, void __user *arg);
-static irqreturn_t he_irq_handler(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t he_irq_handler(int irq, void *dev_id);
 static void he_tasklet(unsigned long data);
 static int he_proc_read(struct atm_dev *dev,loff_t *pos,char *page);
 static int he_start(struct atm_dev *dev);
@@ -2216,7 +2216,7 @@ he_tasklet(unsigned long data)
 }
 
 static irqreturn_t
-he_irq_handler(int irq, void *dev_id, struct pt_regs *regs)
+he_irq_handler(int irq, void *dev_id)
 {
 	unsigned long flags;
 	struct he_dev *he_dev = (struct he_dev * )dev_id;
diff --git a/drivers/atm/horizon.c b/drivers/atm/horizon.c
index 209dba1c70da..33e9ee47392b 100644
--- a/drivers/atm/horizon.c
+++ b/drivers/atm/horizon.c
@@ -1382,12 +1382,10 @@ static inline void rx_data_av_handler (hrz_dev * dev) {
 
 /********** interrupt handler **********/
 
-static irqreturn_t interrupt_handler(int irq, void *dev_id,
-					struct pt_regs *pt_regs) {
+static irqreturn_t interrupt_handler(int irq, void *dev_id) {
   hrz_dev * dev = (hrz_dev *) dev_id;
   u32 int_source;
   unsigned int irq_ok;
-  (void) pt_regs;
   
   PRINTD (DBG_FLOW, "interrupt_handler: %p", dev_id);
   
diff --git a/drivers/atm/idt77252.c b/drivers/atm/idt77252.c
index 7487f0ad68e9..87b17c33b3f9 100644
--- a/drivers/atm/idt77252.c
+++ b/drivers/atm/idt77252.c
@@ -2774,7 +2774,7 @@ idt77252_collect_stat(struct idt77252_dev *card)
 }
 
 static irqreturn_t
-idt77252_interrupt(int irq, void *dev_id, struct pt_regs *ptregs)
+idt77252_interrupt(int irq, void *dev_id)
 {
 	struct idt77252_dev *card = dev_id;
 	u32 stat;
diff --git a/drivers/atm/iphase.c b/drivers/atm/iphase.c
index f20b0b2c06c6..9ed1c60048f0 100644
--- a/drivers/atm/iphase.c
+++ b/drivers/atm/iphase.c
@@ -2195,7 +2195,7 @@ err_out:
 	return -ENOMEM;
 }   
    
-static irqreturn_t ia_int(int irq, void *dev_id, struct pt_regs *regs)  
+static irqreturn_t ia_int(int irq, void *dev_id)  
 {  
    struct atm_dev *dev;  
    IADEV *iadev;  
diff --git a/drivers/atm/lanai.c b/drivers/atm/lanai.c
index b9568e10965a..8895f026bea7 100644
--- a/drivers/atm/lanai.c
+++ b/drivers/atm/lanai.c
@@ -1890,12 +1890,12 @@ static inline void lanai_int_1(struct lanai_dev *lanai, u32 reason)
 		reg_write(lanai, ack, IntAck_Reg);
 }
 
-static irqreturn_t lanai_int(int irq, void *devid, struct pt_regs *regs)
+static irqreturn_t lanai_int(int irq, void *devid)
 {
 	struct lanai_dev *lanai = (struct lanai_dev *) devid;
 	u32 reason;
 
-	(void) irq; (void) regs;	/* unused variables */
+	(void) irq;	/* unused variables */
 
 #ifdef USE_POWERDOWN
 	/*
diff --git a/drivers/atm/nicstar.c b/drivers/atm/nicstar.c
index b8036899e56f..632ede552761 100644
--- a/drivers/atm/nicstar.c
+++ b/drivers/atm/nicstar.c
@@ -214,7 +214,7 @@ static void __devinit ns_init_card_error(ns_dev *card, int error);
 static scq_info *get_scq(int size, u32 scd);
 static void free_scq(scq_info *scq, struct atm_vcc *vcc);
 static void push_rxbufs(ns_dev *, struct sk_buff *);
-static irqreturn_t ns_irq_handler(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t ns_irq_handler(int irq, void *dev_id);
 static int ns_open(struct atm_vcc *vcc);
 static void ns_close(struct atm_vcc *vcc);
 static void fill_tst(ns_dev *card, int n, vc_map *vc);
@@ -1194,7 +1194,7 @@ static void push_rxbufs(ns_dev *card, struct sk_buff *skb)
 
 
 
-static irqreturn_t ns_irq_handler(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t ns_irq_handler(int irq, void *dev_id)
 {
    u32 stat_r;
    ns_dev *card;
diff --git a/drivers/atm/zatm.c b/drivers/atm/zatm.c
index 083c5d3f2e18..7df0f373188e 100644
--- a/drivers/atm/zatm.c
+++ b/drivers/atm/zatm.c
@@ -1012,7 +1012,7 @@ static int start_tx(struct atm_dev *dev)
 /*------------------------------- interrupts --------------------------------*/
 
 
-static irqreturn_t zatm_int(int irq,void *dev_id,struct pt_regs *regs)
+static irqreturn_t zatm_int(int irq,void *dev_id)
 {
 	struct atm_dev *dev;
 	struct zatm_dev *zatm_dev;