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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)
100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/*
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* Copyright (C) 2001, 2002, MontaVista Software Inc.
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* Author: Jun Sun, jsun@mvista.com or jsun@junsun.net
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* Copyright (c) 2003 Maciej W. Rozycki
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*
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* include/asm-mips/time.h
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* header file for the new style time.c file and time services.
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* Please refer to Documentation/mips/time.README.
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*/
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#ifndef _ASM_TIME_H
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#define _ASM_TIME_H
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#include <linux/interrupt.h>
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#include <linux/linkage.h>
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#include <linux/ptrace.h>
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#include <linux/rtc.h>
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#include <linux/spinlock.h>
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extern spinlock_t rtc_lock;
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/*
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* RTC ops. By default, they point to no-RTC functions.
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* rtc_mips_get_time - mktime(year, mon, day, hour, min, sec) in seconds.
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* rtc_mips_set_time - reverse the above translation and set time to RTC.
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* rtc_mips_set_mmss - similar to rtc_set_time, but only min and sec need
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* to be set. Used by RTC sync-up.
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*/
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extern unsigned long (*rtc_mips_get_time)(void);
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extern int (*rtc_mips_set_time)(unsigned long);
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extern int (*rtc_mips_set_mmss)(unsigned long);
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/*
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* Timer interrupt functions.
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* mips_timer_state is needed for high precision timer calibration.
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* mips_timer_ack may be NULL if the interrupt is self-recoverable.
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*/
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extern int (*mips_timer_state)(void);
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extern void (*mips_timer_ack)(void);
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/*
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* High precision timer functions.
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* If mips_hpt_read is NULL, an R4k-compatible timer setup is attempted.
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*/
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extern unsigned int (*mips_hpt_read)(void);
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extern void (*mips_hpt_init)(unsigned int);
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/*
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* to_tm() converts system time back to (year, mon, day, hour, min, sec).
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* It is intended to help implement rtc_set_time() functions.
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* Copied from PPC implementation.
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*/
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extern void to_tm(unsigned long tim, struct rtc_time *tm);
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/*
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* do_gettimeoffset(). By default, this func pointer points to
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* do_null_gettimeoffset(), which leads to the same resolution as HZ.
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* Higher resolution versions are available, which give ~1us resolution.
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*/
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extern unsigned long (*do_gettimeoffset)(void);
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/*
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* high-level timer interrupt routines.
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*/
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extern irqreturn_t timer_interrupt(int irq, void *dev_id);
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/*
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* the corresponding low-level timer interrupt routine.
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*/
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extern asmlinkage void ll_timer_interrupt(int irq, struct pt_regs *regs);
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/*
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* profiling and process accouting is done separately in local_timer_interrupt
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*/
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extern void local_timer_interrupt(int irq, void *dev_id);
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extern asmlinkage void ll_local_timer_interrupt(int irq, struct pt_regs *regs);
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/*
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* board specific routines required by time_init().
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* board_time_init is defaulted to NULL and can remain so.
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* plat_timer_setup must be setup properly in machine setup routine.
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*/
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struct irqaction;
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extern void (*board_time_init)(void);
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extern void plat_timer_setup(struct irqaction *irq);
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/*
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* mips_hpt_frequency - must be set if you intend to use an R4k-compatible
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* counter as a timer interrupt source; otherwise it can be set up
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* automagically with an aid of mips_timer_state.
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*/
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extern unsigned int mips_hpt_frequency;
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#endif /* _ASM_TIME_H */
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