linux/drivers/pci/hotplug
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 Still more typo fixes 2006-10-03 22:36:44 +02:00
Makefile ACPIPHP: use ACPI dock driver 2006-06-28 03:08:06 -04:00
acpi_pcihp.c [PATCH] acpi_pcihp: Add support for _HPX 2006-06-19 14:13:22 -07:00
acpiphp.h acpiphp: add support for ioapic hot-remove 2006-09-26 17:43:54 -07:00
acpiphp_core.c PCI Hotplug: add acpiphp to MAINTAINERS 2006-08-03 13:20:06 -07:00
acpiphp_glue.c acpiphp: add support for ioapic hot-remove 2006-09-26 17:43:54 -07:00
acpiphp_ibm.c sysfs_remove_bin_file: no return value, dump_stack on error 2006-09-25 21:08:39 -07:00
cpci_hotplug.h [PATCH] PCI Hotplug: CPCI update 2005-05-17 14:31:11 -07:00
cpci_hotplug_core.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
cpci_hotplug_pci.c [PATCH] CPCI hotplug: fix resource assignment 2006-08-26 13:05:52 -07:00
cpcihp_generic.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
cpcihp_zt5550.c [PATCH] irq-flags: pci: Use the new IRQF_ constants 2006-07-02 13:58:52 -07:00
cpcihp_zt5550.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cpqphp.h IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
cpqphp_core.c [PATCH] irq-flags: pci: Use the new IRQF_ constants 2006-07-02 13:58:52 -07:00
cpqphp_ctrl.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
cpqphp_nvram.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
cpqphp_nvram.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cpqphp_pci.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
cpqphp_sysfs.c [PATCH] inode_diet: Replace inode.u.generic_ip with inode.i_private 2006-09-27 08:26:17 -07:00
fakephp.c PCI: fix __must_check warnings 2006-09-26 17:43:53 -07:00
ibmphp.h [PATCH] ibmphp: remove TRUE and FALSE 2006-03-23 14:35:17 -08:00
ibmphp_core.c [PATCH] PCI Hotplug: fake NULL pointer dereferences in IBM Hot Plug Controller Driver 2006-06-19 14:13:24 -07:00
ibmphp_ebda.c [PATCH] ibmphp: remove TRUE and FALSE 2006-03-23 14:35:17 -08:00
ibmphp_hpc.c [PATCH] ibmphp: remove TRUE and FALSE 2006-03-23 14:35:17 -08:00
ibmphp_pci.c [PATCH] ibmphp: remove TRUE and FALSE 2006-03-23 14:35:17 -08:00
ibmphp_res.c [PATCH] ibmphp: remove TRUE and FALSE 2006-03-23 14:35:17 -08:00
pci_hotplug.h PCI Hotplug: fix __must_check warnings 2006-09-26 17:43:53 -07:00
pci_hotplug_core.c PCI Hotplug: fix __must_check warnings 2006-09-26 17:43:53 -07:00
pciehp.h pciehp: make pciehp build for powerpc 2006-08-11 14:06:05 -07:00
pciehp_core.c [PATCH] pciehp: Implement get_address callback 2006-06-19 14:13:23 -07:00
pciehp_ctrl.c pciehp - fix wrong return value 2006-09-26 17:43:54 -07:00
pciehp_hpc.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
pciehp_pci.c [PATCH] pciehp: Add missing pci_dev_put 2006-06-19 14:13:23 -07:00
pcihp_skeleton.c PCI Hotplug: cleanup pcihp skeleton code. 2006-09-26 17:43:53 -07:00
rpadlpar.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rpadlpar_core.c [PATCH] sem2mutex: misc static one-file mutexes 2006-03-26 08:56:55 -08:00
rpadlpar_sysfs.c [PATCH] PCI Hotplug: Fix buffer overrun in rpadlpar_sysfs.c 2005-09-22 07:58:25 -07:00
rpaphp.h [PATCH] powerpc/PCI hotplug: cleanup: add prefix 2006-01-31 18:00:13 -08:00
rpaphp_core.c [POWERPC] pseries: Constify & voidify get_property() 2006-07-31 15:55:04 +10:00
rpaphp_pci.c [PATCH] powerpc/PCI hotplug: cleanup: add prefix 2006-01-31 18:00:13 -08:00
rpaphp_slot.c [PATCH] PCI: kzalloc() conversion in drivers/pci 2006-03-23 14:35:17 -08:00
sgi_hotplug.c [PATCH] SGI Hotplug: Incorrect power status 2006-06-19 14:13:23 -07:00
shpchp.h SHPCHP: fix __must_check warnings 2006-09-26 17:43:53 -07:00
shpchp_core.c SHPCHP: fix __must_check warnings 2006-09-26 17:43:53 -07:00
shpchp_ctrl.c [PATCH] shpchp: Cleanup improper info messages 2006-06-19 14:13:24 -07:00
shpchp_hpc.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
shpchp_pci.c [PATCH] acpi_pcihp: Add support for _HPX 2006-06-19 14:13:22 -07:00
shpchp_sysfs.c SHPCHP: fix __must_check warnings 2006-09-26 17:43:53 -07:00