From 7d12e780e003f93433d49ce78cfedf4b4c52adc5 Mon Sep 17 00:00:00 2001 From: David Howells Date: Thu, 5 Oct 2006 14:55:46 +0100 Subject: 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 (cherry picked from 1b16e7ac850969f38b375e511e3fa2f474a33867 commit) --- include/asm-x86_64/apic.h | 2 +- include/asm-x86_64/floppy.h | 6 +++--- include/asm-x86_64/irq_regs.h | 1 + include/asm-x86_64/proto.h | 4 ++-- 4 files changed, 7 insertions(+), 6 deletions(-) create mode 100644 include/asm-x86_64/irq_regs.h (limited to 'include/asm-x86_64') diff --git a/include/asm-x86_64/apic.h b/include/asm-x86_64/apic.h index 9e66d32330c9..e81d0f289f0b 100644 --- a/include/asm-x86_64/apic.h +++ b/include/asm-x86_64/apic.h @@ -77,7 +77,7 @@ 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); diff --git a/include/asm-x86_64/floppy.h b/include/asm-x86_64/floppy.h index 32ff5d132714..6ea13c3806f3 100644 --- a/include/asm-x86_64/floppy.h +++ b/include/asm-x86_64/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-x86_64/irq_regs.h b/include/asm-x86_64/irq_regs.h new file mode 100644 index 000000000000..3dd9c0b70270 --- /dev/null +++ b/include/asm-x86_64/irq_regs.h @@ -0,0 +1 @@ +#include diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h index c28fc2db2171..c181fef786e4 100644 --- a/include/asm-x86_64/proto.h +++ b/include/asm-x86_64/proto.h @@ -66,7 +66,7 @@ extern void free_bootmem_generic(unsigned long phys, unsigned len); extern void load_gs_index(unsigned gs); extern void stop_timer_interrupt(void); -extern void main_timer_handler(struct pt_regs *regs); +extern void main_timer_handler(void); extern unsigned long end_pfn_map; @@ -124,7 +124,7 @@ extern int notsc_setup(char *); extern int gsi_irq_sharing(int gsi); -extern void smp_local_timer_interrupt(struct pt_regs * regs); +extern void smp_local_timer_interrupt(void); long do_arch_prctl(struct task_struct *task, int code, unsigned long addr); -- cgit v1.2.1