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, 22 insertions, 21 deletions

diff --git a/include/asm-i386/apic.h b/include/asm-i386/apic.h
index 3a42b7d..b952957 100644
--- a/include/asm-i386/apic.h
+++ b/include/asm-i386/apic.h
@@ -98,7 +98,7 @@ extern void sync_Arb_IDs (void);
 extern void init_bsp_APIC (void);
 extern void setup_local_APIC (void);
 extern void init_apic_mappings (void);
-extern void smp_local_timer_interrupt (struct pt_regs * regs);
+extern void smp_local_timer_interrupt (void);
 extern void setup_boot_APIC_clock (void);
 extern void setup_secondary_APIC_clock (void);
 extern int APIC_init_uniprocessor (void);
@@ -107,7 +107,7 @@ extern void enable_APIC_timer(void);
 
 extern void enable_NMI_through_LVT0 (void * dummy);
 
-void smp_send_timer_broadcast_ipi(struct pt_regs *regs);
+void smp_send_timer_broadcast_ipi(void);
 void switch_APIC_timer_to_ipi(void *cpumask);
 void switch_ipi_to_APIC_timer(void *cpumask);
 #define ARCH_APICTIMER_STOPS_ON_C3	1
diff --git a/include/asm-i386/arch_hooks.h b/include/asm-i386/arch_hooks.h
index 238cf42..a8c1fca 100644
--- a/include/asm-i386/arch_hooks.h
+++ b/include/asm-i386/arch_hooks.h
@@ -14,7 +14,7 @@
 extern void init_ISA_irqs(void);
 extern void apic_intr_init(void);
 extern void smp_intr_init(void);
-extern irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+extern irqreturn_t timer_interrupt(int irq, void *dev_id);
 
 /* these are the defined hooks */
 extern void intr_init_hook(void);
diff --git a/include/asm-i386/floppy.h b/include/asm-i386/floppy.h
index 359ead6..44ef2f5 100644
--- a/include/asm-i386/floppy.h
+++ b/include/asm-i386/floppy.h
@@ -51,7 +51,7 @@ static char *virtual_dma_addr;
 static int virtual_dma_mode;
 static int doing_pdma;
 
-static irqreturn_t floppy_hardint(int irq, void *dev_id, struct pt_regs * regs)
+static irqreturn_t floppy_hardint(int irq, void *dev_id)
 {
 	register unsigned char st;
 
@@ -63,7 +63,7 @@ static irqreturn_t floppy_hardint(int irq, void *dev_id, struct pt_regs * regs)
 	static int dma_wait=0;
 #endif
 	if (!doing_pdma)
-		return floppy_interrupt(irq, dev_id, regs);
+		return floppy_interrupt(irq, dev_id);
 
 #ifdef TRACE_FLPY_INT
 	if(!calls)
@@ -106,7 +106,7 @@ static irqreturn_t floppy_hardint(int irq, void *dev_id, struct pt_regs * regs)
 		dma_wait=0;
 #endif
 		doing_pdma = 0;
-		floppy_interrupt(irq, dev_id, regs);
+		floppy_interrupt(irq, dev_id);
 		return IRQ_HANDLED;
 	}
 #ifdef TRACE_FLPY_INT
diff --git a/include/asm-i386/hpet.h b/include/asm-i386/hpet.h
index af5d435..e47be9a 100644
--- a/include/asm-i386/hpet.h
+++ b/include/asm-i386/hpet.h
@@ -108,7 +108,7 @@ extern int hpet_set_alarm_time(unsigned char hrs, unsigned char min, unsigned ch
 extern int hpet_set_periodic_freq(unsigned long freq);
 extern int hpet_rtc_dropped_irq(void);
 extern int hpet_rtc_timer_init(void);
-extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id, struct pt_regs *regs);
+extern irqreturn_t hpet_rtc_interrupt(int irq, void *dev_id);
 #endif /* CONFIG_HPET_EMULATE_RTC */
 #endif /* CONFIG_HPET_TIMER */
 #endif /* _I386_HPET_H */
diff --git a/include/asm-i386/hw_irq.h b/include/asm-i386/hw_irq.h
index 88f02a0..8806c7e 100644
--- a/include/asm-i386/hw_irq.h
+++ b/include/asm-i386/hw_irq.h
@@ -41,7 +41,7 @@ fastcall void call_function_interrupt(void);
 fastcall void apic_timer_interrupt(void);
 fastcall void error_interrupt(void);
 fastcall void spurious_interrupt(void);
-fastcall void thermal_interrupt(struct pt_regs *);
+fastcall void thermal_interrupt(void);
 #define platform_legacy_irq(irq)	((irq) < 16)
 #endif
 
diff --git a/include/asm-i386/irq_regs.h b/include/asm-i386/irq_regs.h
new file mode 100644
index 0000000..3dd9c0b
--- /dev/null
+++ b/include/asm-i386/irq_regs.h
@@ -0,0 +1 @@
+#include <asm-generic/irq_regs.h>
diff --git a/include/asm-i386/mach-default/do_timer.h b/include/asm-i386/mach-default/do_timer.h
index 4182c34..7d606e3 100644
--- a/include/asm-i386/mach-default/do_timer.h
+++ b/include/asm-i386/mach-default/do_timer.h
@@ -14,11 +14,11 @@
  *	timer interrupt as a means of triggering reschedules etc.
  **/
 
-static inline void do_timer_interrupt_hook(struct pt_regs *regs)
+static inline void do_timer_interrupt_hook(void)
 {
 	do_timer(1);
 #ifndef CONFIG_SMP
-	update_process_times(user_mode_vm(regs));
+	update_process_times(user_mode_vm(get_irq_regs()));
 #endif
 /*
  * In the SMP case we use the local APIC timer interrupt to do the
@@ -26,10 +26,10 @@ static inline void do_timer_interrupt_hook(struct pt_regs *regs)
  * system, in that case we have to call the local interrupt handler.
  */
 #ifndef CONFIG_X86_LOCAL_APIC
-	profile_tick(CPU_PROFILING, regs);
+	profile_tick(CPU_PROFILING);
 #else
 	if (!using_apic_timer)
-		smp_local_timer_interrupt(regs);
+		smp_local_timer_interrupt();
 #endif
 }
 
diff --git a/include/asm-i386/mach-visws/do_timer.h b/include/asm-i386/mach-visws/do_timer.h
index 8db618c..21cd696 100644
--- a/include/asm-i386/mach-visws/do_timer.h
+++ b/include/asm-i386/mach-visws/do_timer.h
@@ -4,14 +4,14 @@
 #include <asm/i8259.h>
 #include "cobalt.h"
 
-static inline void do_timer_interrupt_hook(struct pt_regs *regs)
+static inline void do_timer_interrupt_hook(void)
 {
 	/* Clear the interrupt */
 	co_cpu_write(CO_CPU_STAT,co_cpu_read(CO_CPU_STAT) & ~CO_STAT_TIMEINTR);
 
 	do_timer(1);
 #ifndef CONFIG_SMP
-	update_process_times(user_mode_vm(regs));
+	update_process_times(user_mode_vm(irq_regs));
 #endif
 /*
  * In the SMP case we use the local APIC timer interrupt to do the
@@ -19,10 +19,10 @@ static inline void do_timer_interrupt_hook(struct pt_regs *regs)
  * system, in that case we have to call the local interrupt handler.
  */
 #ifndef CONFIG_X86_LOCAL_APIC
-	profile_tick(CPU_PROFILING, regs);
+	profile_tick(CPU_PROFILING);
 #else
 	if (!using_apic_timer)
-		smp_local_timer_interrupt(regs);
+		smp_local_timer_interrupt();
 #endif
 }
 
diff --git a/include/asm-i386/mach-voyager/do_timer.h b/include/asm-i386/mach-voyager/do_timer.h
index 099fe9f..04e69c1 100644
--- a/include/asm-i386/mach-voyager/do_timer.h
+++ b/include/asm-i386/mach-voyager/do_timer.h
@@ -1,14 +1,14 @@
 /* defines for inline arch setup functions */
 #include <asm/voyager.h>
 
-static inline void do_timer_interrupt_hook(struct pt_regs *regs)
+static inline void do_timer_interrupt_hook(void)
 {
 	do_timer(1);
 #ifndef CONFIG_SMP
-	update_process_times(user_mode_vm(regs));
+	update_process_times(user_mode_vm(irq_regs));
 #endif
 
-	voyager_timer_interrupt(regs);
+	voyager_timer_interrupt();
 }
 
 static inline int do_timer_overflow(int count)
diff --git a/include/asm-i386/voyager.h b/include/asm-i386/voyager.h
index aaf432d..e74c54aa 100644
--- a/include/asm-i386/voyager.h
+++ b/include/asm-i386/voyager.h
@@ -505,8 +505,8 @@ extern int voyager_memory_detect(int region, __u32 *addr, __u32 *length);
 extern void voyager_smp_intr_init(void);
 extern __u8 voyager_extended_cmos_read(__u16 cmos_address);
 extern void voyager_smp_dump(void);
-extern void voyager_timer_interrupt(struct pt_regs *regs);
-extern void smp_local_timer_interrupt(struct pt_regs * regs);
+extern void voyager_timer_interrupt(void);
+extern void smp_local_timer_interrupt(void);
 extern void voyager_power_off(void);
 extern void smp_voyager_power_off(void *dummy);
 extern void voyager_restart(void);