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)

4 files changed, 15 insertions, 15 deletions

diff --git a/sound/oss/dmasound/dmasound_atari.c b/sound/oss/dmasound/dmasound_atari.c
index dc31373069a..285239d64b8 100644
--- a/sound/oss/dmasound/dmasound_atari.c
+++ b/sound/oss/dmasound/dmasound_atari.c
@@ -133,7 +133,7 @@ static int FalconSetFormat(int format);
 static int FalconSetVolume(int volume);
 static void AtaPlayNextFrame(int index);
 static void AtaPlay(void);
-static irqreturn_t AtaInterrupt(int irq, void *dummy, struct pt_regs *fp);
+static irqreturn_t AtaInterrupt(int irq, void *dummy);
 
 /*** Mid level stuff *********************************************************/
 
@@ -1257,7 +1257,7 @@ static void AtaPlay(void)
 }
 
 
-static irqreturn_t AtaInterrupt(int irq, void *dummy, struct pt_regs *fp)
+static irqreturn_t AtaInterrupt(int irq, void *dummy)
 {
 #if 0
 	/* ++TeSche: if you should want to test this... */
diff --git a/sound/oss/dmasound/dmasound_awacs.c b/sound/oss/dmasound/dmasound_awacs.c
index 9ae659f8243..3bd19c36fcd 100644
--- a/sound/oss/dmasound/dmasound_awacs.c
+++ b/sound/oss/dmasound/dmasound_awacs.c
@@ -281,9 +281,9 @@ static int PMacSetFormat(int format);
 static int PMacSetVolume(int volume);
 static void PMacPlay(void);
 static void PMacRecord(void);
-static irqreturn_t pmac_awacs_tx_intr(int irq, void *devid, struct pt_regs *regs);
-static irqreturn_t pmac_awacs_rx_intr(int irq, void *devid, struct pt_regs *regs);
-static irqreturn_t pmac_awacs_intr(int irq, void *devid, struct pt_regs *regs);
+static irqreturn_t pmac_awacs_tx_intr(int irq, void *devid);
+static irqreturn_t pmac_awacs_rx_intr(int irq, void *devid);
+static irqreturn_t pmac_awacs_intr(int irq, void *devid);
 static void awacs_write(int val);
 static int awacs_get_volume(int reg, int lshift);
 static int awacs_volume_setter(int volume, int n, int mute, int lshift);
@@ -398,7 +398,7 @@ read_audio_gpio(int gpio_addr)
  * Headphone interrupt via GPIO (Tumbler, Snapper, DACA)
  */
 static irqreturn_t
-headphone_intr(int irq, void *devid, struct pt_regs *regs)
+headphone_intr(int irq, void *devid)
 {
 	unsigned long flags;
 
@@ -1037,7 +1037,7 @@ static void PMacRecord(void)
 */
 
 static irqreturn_t
-pmac_awacs_tx_intr(int irq, void *devid, struct pt_regs *regs)
+pmac_awacs_tx_intr(int irq, void *devid)
 {
 	int i = write_sq.front;
 	int stat;
@@ -1129,7 +1129,7 @@ printk("dmasound_pmac: tx-irq: xfer died - patching it up...\n") ;
 
 
 static irqreturn_t
-pmac_awacs_rx_intr(int irq, void *devid, struct pt_regs *regs)
+pmac_awacs_rx_intr(int irq, void *devid)
 {
 	int stat ;
 	/* For some reason on my PowerBook G3, I get one interrupt
@@ -1212,7 +1212,7 @@ printk("dmasound_pmac: rx-irq: DIED - attempting resurection\n");
 
 
 static irqreturn_t
-pmac_awacs_intr(int irq, void *devid, struct pt_regs *regs)
+pmac_awacs_intr(int irq, void *devid)
 {
 	int ctrl;
 	int status;
diff --git a/sound/oss/dmasound/dmasound_paula.c b/sound/oss/dmasound/dmasound_paula.c
index 68e1d8f6c35..90fc058e115 100644
--- a/sound/oss/dmasound/dmasound_paula.c
+++ b/sound/oss/dmasound/dmasound_paula.c
@@ -82,7 +82,7 @@ static int AmiSetVolume(int volume);
 static int AmiSetTreble(int treble);
 static void AmiPlayNextFrame(int index);
 static void AmiPlay(void);
-static irqreturn_t AmiInterrupt(int irq, void *dummy, struct pt_regs *fp);
+static irqreturn_t AmiInterrupt(int irq, void *dummy);
 
 #ifdef CONFIG_HEARTBEAT
 
@@ -556,7 +556,7 @@ static void AmiPlay(void)
 }
 
 
-static irqreturn_t AmiInterrupt(int irq, void *dummy, struct pt_regs *fp)
+static irqreturn_t AmiInterrupt(int irq, void *dummy)
 {
 	int minframes = 1;
 
diff --git a/sound/oss/dmasound/dmasound_q40.c b/sound/oss/dmasound/dmasound_q40.c
index e2081f32b0c..b3379dd7ca5 100644
--- a/sound/oss/dmasound/dmasound_q40.c
+++ b/sound/oss/dmasound/dmasound_q40.c
@@ -48,8 +48,8 @@ static int Q40SetFormat(int format);
 static int Q40SetVolume(int volume);
 static void Q40PlayNextFrame(int index);
 static void Q40Play(void);
-static irqreturn_t Q40StereoInterrupt(int irq, void *dummy, struct pt_regs *fp);
-static irqreturn_t Q40MonoInterrupt(int irq, void *dummy, struct pt_regs *fp);
+static irqreturn_t Q40StereoInterrupt(int irq, void *dummy);
+static irqreturn_t Q40MonoInterrupt(int irq, void *dummy);
 static void Q40Interrupt(void);
 
 
@@ -451,7 +451,7 @@ static void Q40Play(void)
 	spin_unlock_irqrestore(&dmasound.lock, flags);
 }
 
-static irqreturn_t Q40StereoInterrupt(int irq, void *dummy, struct pt_regs *fp)
+static irqreturn_t Q40StereoInterrupt(int irq, void *dummy)
 {
 	spin_lock(&dmasound.lock);
         if (q40_sc>1){
@@ -463,7 +463,7 @@ static irqreturn_t Q40StereoInterrupt(int irq, void *dummy, struct pt_regs *fp)
 	spin_unlock(&dmasound.lock);
 	return IRQ_HANDLED;
 }
-static irqreturn_t Q40MonoInterrupt(int irq, void *dummy, struct pt_regs *fp)
+static irqreturn_t Q40MonoInterrupt(int irq, void *dummy)
 {
 	spin_lock(&dmasound.lock);
         if (q40_sc>0){