OpenCloudOS-Kernel/drivers/message/i2o
David Howells 7d12e780e0 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)
2006-10-05 15:10:12 +01:00
..
Kconfig [PATCH] BLOCK: Make it possible to disable the block layer [try #6] 2006-09-30 20:52:31 +02:00
Makefile [PATCH] I2O: new sysfs attributes and Adaptec specific block device access and 64-bit DMA support 2005-06-24 00:05:28 -07:00
README Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
README.ioctl spelling: s/retreive/retrieve/ 2006-01-10 00:10:13 +01:00
bus-osm.c [PATCH] I2O: Beautifying 2006-01-06 08:33:54 -08:00
config-osm.c [PATCH] I2O: Optimizing 2006-01-06 08:33:54 -08:00
core.h [PATCH] proper prototype for drivers/message/i2o/device.c:i2o_parm_issue() 2006-07-10 13:24:26 -07:00
debug.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
device.c [PATCH] I2O: Lindent run 2006-01-06 08:33:54 -08:00
driver.c [PATCH] I2O: Optimizing 2006-01-06 08:33:54 -08:00
exec-osm.c [PATCH] I2O: Bugfixes to get I2O working again 2006-06-10 11:02:05 -07:00
i2o_block.c [PATCH] Split struct request ->flags into two parts 2006-09-30 20:23:37 +02:00
i2o_block.h [PATCH] I2O: Lindent run and replacement of printk through osm printing functions 2005-06-24 00:05:29 -07:00
i2o_config.c [PATCH] proper prototype for drivers/message/i2o/device.c:i2o_parm_issue() 2006-07-10 13:24:26 -07:00
i2o_lan.h [PATCH] I2O: Lindent run 2006-01-06 08:33:54 -08:00
i2o_proc.c [PATCH] mark f_ops const in the inode 2006-03-28 09:16:05 -08:00
i2o_scsi.c [SCSI] remove scsi_request infrastructure 2006-06-10 16:24:40 -05:00
iop.c Merge master.kernel.org:/pub/scm/linux/kernel/git/gregkh/pci-2.6 2006-06-29 10:49:17 -07:00
pci.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00

README

	Linux I2O Support	(c) Copyright 1999 Red Hat Software
					and others.

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version
	2 of the License, or (at your option) any later version.

AUTHORS (so far)

Alan Cox, Building Number Three Ltd.
	Core code, SCSI and Block OSMs

Steve Ralston, LSI Logic Corp.
	Debugging SCSI and Block OSM

Deepak Saxena, Intel Corp.
	Various core/block extensions
	/proc interface, bug fixes
	Ioctl interfaces for control
	Debugging LAN OSM

Philip Rumpf
	Fixed assorted dumb SMP locking bugs

Juha Sievanen, University of Helsinki Finland
	LAN OSM code
	/proc interface to LAN class
	Bug fixes
	Core code extensions

Auvo Häkkinen, University of Helsinki Finland
	LAN OSM code
	/Proc interface to LAN class
	Bug fixes
	Core code extensions

Taneli Vähäkangas, University of Helsinki Finland
	Fixes to i2o_config

CREDITS

	This work was made possible by 

Red Hat Software
	Funding for the Building #3 part of the project

Symbios Logic (Now LSI)
	Host adapters, hints, known to work platforms when I hit
	compatibility problems

BoxHill Corporation
	Loan of initial FibreChannel disk array used for development work.

European Comission
	Funding the work done by the University of Helsinki

SysKonnect
        Loan of FDDI and Gigabit Ethernet cards

ASUSTeK
        Loan of I2O motherboard 

STATUS:

o	The core setup works within limits.
o	The scsi layer seems to almost work. 
           I'm still chasing down the hang bug.
o	The block OSM is mostly functional
o	LAN OSM works with FDDI and Ethernet cards.

TO DO:

General:
o	Provide hidden address space if asked
o	Long term message flow control
o	PCI IOP's without interrupts are not supported yet
o	Push FAIL handling into the core
o	DDM control interfaces for module load etc
o       Add I2O 2.0 support (Deffered to 2.5 kernel)

Block:
o	Multiple major numbers
o	Read ahead and cache handling stuff. Talk to Ingo and people
o	Power management
o	Finish Media changers

SCSI:
o	Find the right way to associate drives/luns/busses

Lan:	
o	Performance tuning
o	Test Fibre Channel code

Tape:
o	Anyone seen anything implementing this ?
           (D.S: Will attempt to do so if spare cycles permit)