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)

12 files changed, 15 insertions, 16 deletions

diff --git a/drivers/video/amifb.c b/drivers/video/amifb.c
index f1ba54f4fc39..a4e3fca05891 100644
--- a/drivers/video/amifb.c
+++ b/drivers/video/amifb.c
@@ -1144,7 +1144,7 @@ static void amifb_deinit(void);
          */
 
 static int flash_cursor(void);
-static irqreturn_t amifb_interrupt(int irq, void *dev_id, struct pt_regs *fp);
+static irqreturn_t amifb_interrupt(int irq, void *dev_id);
 static u_long chipalloc(u_long size);
 static void chipfree(void);
 
@@ -2492,7 +2492,7 @@ static int flash_cursor(void)
          * VBlank Display Interrupt
          */
 
-static irqreturn_t amifb_interrupt(int irq, void *dev_id, struct pt_regs *fp)
+static irqreturn_t amifb_interrupt(int irq, void *dev_id)
 {
         if (do_vmode_pan || do_vmode_full)
                 ami_update_display();
diff --git a/drivers/video/arcfb.c b/drivers/video/arcfb.c
index 70dd8115a4d8..ab34b96acc31 100644
--- a/drivers/video/arcfb.c
+++ b/drivers/video/arcfb.c
@@ -218,8 +218,7 @@ static int arcfb_pan_display(struct fb_var_screeninfo *var,
         return -EINVAL;
 }
 
-static irqreturn_t arcfb_interrupt(int vec, void *dev_instance,
-                struct pt_regs *regs)
+static irqreturn_t arcfb_interrupt(int vec, void *dev_instance)
 {
         struct fb_info *info = dev_instance;
         unsigned char ctl2status;
diff --git a/drivers/video/atafb.c b/drivers/video/atafb.c
index 5831893bf7a0..02c41a626fa2 100644
--- a/drivers/video/atafb.c
+++ b/drivers/video/atafb.c
@@ -1521,7 +1521,7 @@ static void falcon_set_par( struct atafb_par *par )
 }
 
 
-static irqreturn_t falcon_vbl_switcher( int irq, void *dummy, struct pt_regs *fp )
+static irqreturn_t falcon_vbl_switcher( int irq, void *dummy )
 {
         struct falcon_hw *hw = &f_new_mode;
 
diff --git a/drivers/video/aty/atyfb_base.c b/drivers/video/aty/atyfb_base.c
index b45c9fd1b330..b77b30923928 100644
--- a/drivers/video/aty/atyfb_base.c
+++ b/drivers/video/aty/atyfb_base.c
@@ -1532,7 +1532,7 @@ static int atyfb_open(struct fb_info *info, int user)
         return (0);
 }
 
-static irqreturn_t aty_irq(int irq, void *dev_id, struct pt_regs *fp)
+static irqreturn_t aty_irq(int irq, void *dev_id)
 {
         struct atyfb_par *par = dev_id;
         int handled = 0;
diff --git a/drivers/video/au1200fb.c b/drivers/video/au1200fb.c
index c6a5f0ccc107..dbf4ec3f6d57 100644
--- a/drivers/video/au1200fb.c
+++ b/drivers/video/au1200fb.c
@@ -1545,7 +1545,7 @@ static struct fb_ops au1200fb_fb_ops = {
 
 /*-------------------------------------------------------------------------*/
 
-static irqreturn_t au1200fb_handle_irq(int irq, void* dev_id, struct pt_regs *regs)
+static irqreturn_t au1200fb_handle_irq(int irq, void* dev_id)
 {
         /* Nothing to do for now, just clear any pending interrupt */
         lcd->intstatus = lcd->intstatus;
diff --git a/drivers/video/console/fbcon.c b/drivers/video/console/fbcon.c
index 8c041daa3a15..302174b8e477 100644
--- a/drivers/video/console/fbcon.c
+++ b/drivers/video/console/fbcon.c
@@ -204,7 +204,7 @@ static struct class_device *fbcon_class_device;
  */
 static int vbl_detected;
 
-static irqreturn_t fb_vbl_detect(int irq, void *dummy, struct pt_regs *fp)
+static irqreturn_t fb_vbl_detect(int irq, void *dummy)
 {
         vbl_detected++;
         return IRQ_HANDLED;
@@ -414,7 +414,7 @@ static void fb_flashcursor(void *private)
 
 #if defined(CONFIG_ATARI) || defined(CONFIG_MAC)
 static int cursor_blink_rate;
-static irqreturn_t fb_vbl_handler(int irq, void *dev_id, struct pt_regs *fp)
+static irqreturn_t fb_vbl_handler(int irq, void *dev_id)
 {
         struct fb_info *info = dev_id;
 
diff --git a/drivers/video/intelfb/intelfbhw.c b/drivers/video/intelfb/intelfbhw.c
index f887f1efd3fe..eeeeff9a09eb 100644
--- a/drivers/video/intelfb/intelfbhw.c
+++ b/drivers/video/intelfb/intelfbhw.c
@@ -1952,7 +1952,7 @@ intelfbhw_cursor_reset(struct intelfb_info *dinfo) {
 }
 
 static irqreturn_t
-intelfbhw_irq(int irq, void *dev_id, struct pt_regs *fp) {
+intelfbhw_irq(int irq, void *dev_id) {
         int handled = 0;
         u16 tmp;
         struct intelfb_info *dinfo = (struct intelfb_info *)dev_id;
diff --git a/drivers/video/matrox/matroxfb_base.c b/drivers/video/matrox/matroxfb_base.c
index 7acf01c181ee..e9b4115fcad0 100644
--- a/drivers/video/matrox/matroxfb_base.c
+++ b/drivers/video/matrox/matroxfb_base.c
@@ -198,7 +198,7 @@ static void matroxfb_crtc1_panpos(WPMINFO2) {
         }
 }
 
-static irqreturn_t matrox_irq(int irq, void *dev_id, struct pt_regs *fp)
+static irqreturn_t matrox_irq(int irq, void *dev_id)
 {
         u_int32_t status;
         int handled = 0;
diff --git a/drivers/video/pvr2fb.c b/drivers/video/pvr2fb.c
index 78dc59a1751b..c7bc80921f16 100644
--- a/drivers/video/pvr2fb.c
+++ b/drivers/video/pvr2fb.c
@@ -209,7 +209,7 @@ static int pvr2fb_set_par(struct fb_info *info);
 static void pvr2_update_display(struct fb_info *info);
 static void pvr2_init_display(struct fb_info *info);
 static void pvr2_do_blank(void);
-static irqreturn_t pvr2fb_interrupt(int irq, void *dev_id, struct pt_regs *fp);
+static irqreturn_t pvr2fb_interrupt(int irq, void *dev_id);
 static int pvr2_init_cable(void);
 static int pvr2_get_param(const struct pvr2_params *p, const char *s,
                             int val, int size);
@@ -626,7 +626,7 @@ static void pvr2_do_blank(void)
         is_blanked = do_blank > 0 ? do_blank : 0;
 }
 
-static irqreturn_t pvr2fb_interrupt(int irq, void *dev_id, struct pt_regs *fp)
+static irqreturn_t pvr2fb_interrupt(int irq, void *dev_id)
 {
         struct fb_info *info = dev_id;
 
diff --git a/drivers/video/pxafb.c b/drivers/video/pxafb.c
index 3bc5da4a57ca..8a8ae55a7403 100644
--- a/drivers/video/pxafb.c
+++ b/drivers/video/pxafb.c
@@ -846,7 +846,7 @@ static void pxafb_disable_controller(struct pxafb_info *fbi)
 /*
  *  pxafb_handle_irq: Handle 'LCD DONE' interrupts.
  */
-static irqreturn_t pxafb_handle_irq(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t pxafb_handle_irq(int irq, void *dev_id)
 {
         struct pxafb_info *fbi = dev_id;
         unsigned int lcsr = LCSR;
diff --git a/drivers/video/s3c2410fb.c b/drivers/video/s3c2410fb.c
index ad3bdd6f1ac1..59407343cc73 100644
--- a/drivers/video/s3c2410fb.c
+++ b/drivers/video/s3c2410fb.c
@@ -614,7 +614,7 @@ static void s3c2410fb_write_palette(struct s3c2410fb_info *fbi)
         }
 }
 
-static irqreturn_t s3c2410fb_irq(int irq, void *dev_id, struct pt_regs *r)
+static irqreturn_t s3c2410fb_irq(int irq, void *dev_id)
 {
         struct s3c2410fb_info *fbi = dev_id;
         unsigned long lcdirq = readl(S3C2410_LCDINTPND);
diff --git a/drivers/video/sa1100fb.c b/drivers/video/sa1100fb.c
index a2e6e7205d7e..cd10b18150b8 100644
--- a/drivers/video/sa1100fb.c
+++ b/drivers/video/sa1100fb.c
@@ -1085,7 +1085,7 @@ static void sa1100fb_disable_controller(struct sa1100fb_info *fbi)
 /*
  *  sa1100fb_handle_irq: Handle 'LCD DONE' interrupts.
  */
-static irqreturn_t sa1100fb_handle_irq(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t sa1100fb_handle_irq(int irq, void *dev_id)
 {
         struct sa1100fb_info *fbi = dev_id;
         unsigned int lcsr = LCSR;