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, 16 insertions, 17 deletions

diff --git a/drivers/net/tokenring/3c359.c b/drivers/net/tokenring/3c359.c
index 412390b..7580bde 100644
--- a/drivers/net/tokenring/3c359.c
+++ b/drivers/net/tokenring/3c359.c
@@ -130,7 +130,7 @@ static int xl_xmit(struct sk_buff *skb, struct net_device *dev);
 static void xl_dn_comp(struct net_device *dev); 
 static int xl_close(struct net_device *dev);
 static void xl_set_rx_mode(struct net_device *dev);
-static irqreturn_t xl_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t xl_interrupt(int irq, void *dev_id);
 static struct net_device_stats * xl_get_stats(struct net_device *dev);
 static int xl_set_mac_address(struct net_device *dev, void *addr) ; 
 static void xl_arb_cmd(struct net_device *dev);
@@ -1042,7 +1042,7 @@ static void xl_freemem(struct net_device *dev)
 	return  ; 
 }
 
-static irqreturn_t xl_interrupt(int irq, void *dev_id, struct pt_regs *regs) 
+static irqreturn_t xl_interrupt(int irq, void *dev_id) 
 {
 	struct net_device *dev = (struct net_device *)dev_id;
  	struct xl_private *xl_priv =(struct xl_private *)dev->priv;
diff --git a/drivers/net/tokenring/ibmtr.c b/drivers/net/tokenring/ibmtr.c
index 4470025..bfe5986 100644
--- a/drivers/net/tokenring/ibmtr.c
+++ b/drivers/net/tokenring/ibmtr.c
@@ -197,7 +197,7 @@ static void 	open_sap(unsigned char type, struct net_device *dev);
 static void 	tok_set_multicast_list(struct net_device *dev);
 static int 	tok_send_packet(struct sk_buff *skb, struct net_device *dev);
 static int 	tok_close(struct net_device *dev);
-static irqreturn_t tok_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t tok_interrupt(int irq, void *dev_id);
 static void 	initial_tok_int(struct net_device *dev);
 static void 	tr_tx(struct net_device *dev);
 static void 	tr_rx(struct net_device *dev);
@@ -1166,7 +1166,7 @@ static void dir_open_adapter (struct net_device *dev)
 
 /******************************************************************************/
 
-static irqreturn_t tok_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t tok_interrupt(int irq, void *dev_id)
 {
 	unsigned char status;
 	/*  unsigned char status_even ; */
@@ -1178,7 +1178,7 @@ static irqreturn_t tok_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 
 	dev = dev_id;
 #if TR_VERBOSE
-	DPRINTK("Int from tok_driver, dev : %p irq%d regs=%p\n", dev,irq,regs);
+	DPRINTK("Int from tok_driver, dev : %p irq%d\n", dev,irq);
 #endif
 	ti = (struct tok_info *) dev->priv;
 	if (ti->sram_phys & 1)
diff --git a/drivers/net/tokenring/lanstreamer.c b/drivers/net/tokenring/lanstreamer.c
index bfc8c3e..e999feb 100644
--- a/drivers/net/tokenring/lanstreamer.c
+++ b/drivers/net/tokenring/lanstreamer.c
@@ -206,8 +206,7 @@ static int streamer_open(struct net_device *dev);
 static int streamer_xmit(struct sk_buff *skb, struct net_device *dev);
 static int streamer_close(struct net_device *dev);
 static void streamer_set_rx_mode(struct net_device *dev);
-static irqreturn_t streamer_interrupt(int irq, void *dev_id,
-			       struct pt_regs *regs);
+static irqreturn_t streamer_interrupt(int irq, void *dev_id);
 static struct net_device_stats *streamer_get_stats(struct net_device *dev);
 static int streamer_set_mac_address(struct net_device *dev, void *addr);
 static void streamer_arb_cmd(struct net_device *dev);
@@ -1028,7 +1027,7 @@ static void streamer_rx(struct net_device *dev)
 	}			/* end for all completed rx descriptors */
 }
 
-static irqreturn_t streamer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t streamer_interrupt(int irq, void *dev_id)
 {
 	struct net_device *dev = (struct net_device *) dev_id;
 	struct streamer_private *streamer_priv =
diff --git a/drivers/net/tokenring/madgemc.c b/drivers/net/tokenring/madgemc.c
index 666bbaa..ed274d6 100644
--- a/drivers/net/tokenring/madgemc.c
+++ b/drivers/net/tokenring/madgemc.c
@@ -70,7 +70,7 @@ static void madgemc_setregpage(struct net_device *dev, int page);
 static void madgemc_setsifsel(struct net_device *dev, int val);
 static void madgemc_setint(struct net_device *dev, int val);
 
-static irqreturn_t madgemc_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t madgemc_interrupt(int irq, void *dev_id);
 
 /*
  * These work around paging, however they don't guarentee you're on the
@@ -417,7 +417,7 @@ getout:
  * exhausted all contiguous interrupts.
  *
  */
-static irqreturn_t madgemc_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t madgemc_interrupt(int irq, void *dev_id)
 {
 	int pending,reg1;
 	struct net_device *dev;
@@ -451,7 +451,7 @@ static irqreturn_t madgemc_interrupt(int irq, void *dev_id, struct pt_regs *regs
 			outb(reg1, dev->base_addr + MC_CONTROL_REG1);
 
 			/* Continue handling as normal */
-			tms380tr_interrupt(irq, dev_id, regs);
+			tms380tr_interrupt(irq, dev_id);
 
 			pending = SIFREADW(SIFSTS); /* restart - the SIF way */
 
diff --git a/drivers/net/tokenring/olympic.c b/drivers/net/tokenring/olympic.c
index 8583148..cd142d0 100644
--- a/drivers/net/tokenring/olympic.c
+++ b/drivers/net/tokenring/olympic.c
@@ -185,7 +185,7 @@ static int olympic_xmit(struct sk_buff *skb, struct net_device *dev);
 static int olympic_close(struct net_device *dev);
 static void olympic_set_rx_mode(struct net_device *dev);
 static void olympic_freemem(struct net_device *dev) ;  
-static irqreturn_t olympic_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t olympic_interrupt(int irq, void *dev_id);
 static struct net_device_stats * olympic_get_stats(struct net_device *dev);
 static int olympic_set_mac_address(struct net_device *dev, void *addr) ; 
 static void olympic_arb_cmd(struct net_device *dev);
@@ -925,7 +925,7 @@ static void olympic_freemem(struct net_device *dev)
 	return ; 
 }
  
-static irqreturn_t olympic_interrupt(int irq, void *dev_id, struct pt_regs *regs) 
+static irqreturn_t olympic_interrupt(int irq, void *dev_id) 
 {
 	struct net_device *dev= (struct net_device *)dev_id;
 	struct olympic_private *olympic_priv=(struct olympic_private *)dev->priv;
diff --git a/drivers/net/tokenring/smctr.c b/drivers/net/tokenring/smctr.c
index 85a7f79..9bd4cba 100644
--- a/drivers/net/tokenring/smctr.c
+++ b/drivers/net/tokenring/smctr.c
@@ -141,7 +141,7 @@ static int smctr_init_shared_memory(struct net_device *dev);
 static int smctr_init_tx_bdbs(struct net_device *dev);
 static int smctr_init_tx_fcbs(struct net_device *dev);
 static int smctr_internal_self_test(struct net_device *dev);
-static irqreturn_t smctr_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+static irqreturn_t smctr_interrupt(int irq, void *dev_id);
 static int smctr_issue_enable_int_cmd(struct net_device *dev,
         __u16 interrupt_enable_mask);
 static int smctr_issue_int_ack(struct net_device *dev, __u16 iack_code,
@@ -1980,7 +1980,7 @@ static int smctr_internal_self_test(struct net_device *dev)
 /*
  * The typical workload of the driver: Handle the network interface interrupts.
  */
-static irqreturn_t smctr_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+static irqreturn_t smctr_interrupt(int irq, void *dev_id)
 {
         struct net_device *dev = dev_id;
         struct net_local *tp;
diff --git a/drivers/net/tokenring/tms380tr.c b/drivers/net/tokenring/tms380tr.c
index c192559..c0ab6e4 100644
--- a/drivers/net/tokenring/tms380tr.c
+++ b/drivers/net/tokenring/tms380tr.c
@@ -744,7 +744,7 @@ static void tms380tr_timer_chk(unsigned long data)
 /*
  * The typical workload of the driver: Handle the network interface interrupts.
  */
-irqreturn_t tms380tr_interrupt(int irq, void *dev_id, struct pt_regs *regs)
+irqreturn_t tms380tr_interrupt(int irq, void *dev_id)
 {
 	struct net_device *dev = dev_id;
 	struct net_local *tp;
diff --git a/drivers/net/tokenring/tms380tr.h b/drivers/net/tokenring/tms380tr.h
index 30452c6..2a16078 100644
--- a/drivers/net/tokenring/tms380tr.h
+++ b/drivers/net/tokenring/tms380tr.h
@@ -16,7 +16,7 @@
 /* module prototypes */
 int tms380tr_open(struct net_device *dev);
 int tms380tr_close(struct net_device *dev);
-irqreturn_t tms380tr_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+irqreturn_t tms380tr_interrupt(int irq, void *dev_id);
 int tmsdev_init(struct net_device *dev, struct device *pdev);
 void tmsdev_term(struct net_device *dev);
 void tms380tr_wait(unsigned long time);