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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)
64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
/*
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* linux/drivers/sound/vidc.h
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*
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* Copyright (C) 1997 Russell King <rmk@arm.linux.org.uk>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* VIDC sound function prototypes
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*/
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/* vidc_fill.S */
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/*
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* Filler routines for different channels and sample sizes
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*/
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extern unsigned long vidc_fill_1x8_u(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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extern unsigned long vidc_fill_2x8_u(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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extern unsigned long vidc_fill_1x8_s(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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extern unsigned long vidc_fill_2x8_s(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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extern unsigned long vidc_fill_1x16_s(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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extern unsigned long vidc_fill_2x16_s(unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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/*
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* DMA Interrupt handler
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*/
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extern irqreturn_t vidc_sound_dma_irq(int irqnr, void *ref);
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/*
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* Filler routine pointer
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*/
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extern unsigned long (*vidc_filler) (unsigned long ibuf, unsigned long iend,
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unsigned long obuf, int mask);
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/*
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* Virtual DMA buffer exhausted
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*/
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extern irqreturn_t (*dma_interrupt) (void);
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/*
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* Virtual DMA buffer addresses
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*/
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extern unsigned long dma_start, dma_count, dma_bufsize;
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extern unsigned long dma_buf[2], dma_pbuf[2];
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/* vidc_synth.c */
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extern void vidc_synth_init(struct address_info *hw_config);
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extern void vidc_synth_exit(struct address_info *hw_config);
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extern int vidc_synth_get_volume(void);
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extern int vidc_synth_set_volume(int vol);
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