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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
1.6 KiB
C
64 lines
1.6 KiB
C
/* -*- linux-c -*-
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*
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* $Id: sysrq.h,v 1.3 1997/07/17 11:54:33 mj Exp $
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*
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* Linux Magic System Request Key Hacks
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*
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* (c) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
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*
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* (c) 2000 Crutcher Dunnavant <crutcher+kernel@datastacks.com>
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* overhauled to use key registration
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* based upon discusions in irc://irc.openprojects.net/#kernelnewbies
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*/
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#ifndef _LINUX_SYSRQ_H
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#define _LINUX_SYSRQ_H
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struct pt_regs;
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struct tty_struct;
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/* Possible values of bitmask for enabling sysrq functions */
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/* 0x0001 is reserved for enable everything */
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#define SYSRQ_ENABLE_LOG 0x0002
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#define SYSRQ_ENABLE_KEYBOARD 0x0004
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#define SYSRQ_ENABLE_DUMP 0x0008
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#define SYSRQ_ENABLE_SYNC 0x0010
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#define SYSRQ_ENABLE_REMOUNT 0x0020
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#define SYSRQ_ENABLE_SIGNAL 0x0040
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#define SYSRQ_ENABLE_BOOT 0x0080
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#define SYSRQ_ENABLE_RTNICE 0x0100
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struct sysrq_key_op {
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void (*handler)(int, struct tty_struct *);
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char *help_msg;
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char *action_msg;
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int enable_mask;
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};
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#ifdef CONFIG_MAGIC_SYSRQ
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/* Generic SysRq interface -- you may call it from any device driver, supplying
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* ASCII code of the key, pointer to registers and kbd/tty structs (if they
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* are available -- else NULL's).
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*/
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void handle_sysrq(int, struct tty_struct *);
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void __handle_sysrq(int, struct tty_struct *, int check_mask);
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int register_sysrq_key(int, struct sysrq_key_op *);
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int unregister_sysrq_key(int, struct sysrq_key_op *);
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struct sysrq_key_op *__sysrq_get_key_op(int key);
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#else
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static inline int __reterr(void)
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{
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return -EINVAL;
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}
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#define register_sysrq_key(ig,nore) __reterr()
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#define unregister_sysrq_key(ig,nore) __reterr()
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#endif
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#endif /* _LINUX_SYSRQ_H */
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