linux/kernel
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
..
irq IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
power IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
time [PATCH] kernel/time/ntp.c: possible cleanups 2006-10-01 00:39:27 -07:00
.gitignore
Kconfig.hz
Kconfig.preempt
Makefile [PATCH] srcu-3: RCU variant permitting read-side blocking 2006-10-04 07:55:30 -07:00
acct.c [PATCH] csa: convert CONFIG tag for extended accounting routines 2006-10-01 00:39:29 -07:00
audit.c [PATCH] selinux: rename selinux_ctxid_to_string 2006-09-26 08:48:52 -07:00
audit.h [PATCH] audit: AUDIT_PERM support 2006-09-11 13:32:30 -04:00
auditfilter.c [PATCH] arch filter lists with < or > should not be accepted 2006-10-04 08:31:16 -04:00
auditsc.c [PATCH] name_count array overrun 2006-10-04 08:31:21 -04:00
capability.c [PATCH] pidspace: is_init() 2006-09-29 09:18:12 -07:00
compat.c [PATCH] BLOCK: Revert patch to hack around undeclared sigset_t in linux/compat.h 2006-10-02 08:03:31 -07:00
configs.c
cpu.c [PATCH] Disable CPU hotplug during suspend 2006-09-26 08:48:59 -07:00
cpuset.c [PATCH] r/o bind mount prepwork: inc_nlink() helper 2006-10-01 00:39:30 -07:00
delayacct.c [PATCH] task delay accounting fixes 2006-09-01 11:39:08 -07:00
dma.c [PATCH] kernel-doc for kernel/dma.c 2006-10-03 08:03:41 -07:00
exec_domain.c
exit.c [PATCH] namespaces: exit_task_namespaces() invalidates nsproxy 2006-10-02 07:57:21 -07:00
extable.c
fork.c [PATCH] IPC namespace - utils 2006-10-02 07:57:22 -07:00
futex.c [PATCH] file: modify struct fown_struct to use a struct pid 2006-10-02 07:57:14 -07:00
futex_compat.c [PATCH] futex: Apply recent futex fixes to futex_compat 2006-08-06 08:57:49 -07:00
hrtimer.c [PATCH] posix-timers: Fix clock_nanosleep() doesn't return the remaining time in compatibility mode 2006-09-29 09:18:15 -07:00
itimer.c
kallsyms.c [PATCH] Create kallsyms_lookup_size_offset() 2006-10-03 08:03:41 -07:00
kexec.c [PATCH] kexec warning fix 2006-09-29 09:18:15 -07:00
kfifo.c [PATCH] memory ordering in __kfifo primitives 2006-09-29 09:18:13 -07:00
kmod.c [PATCH] introduce kernel_execve 2006-10-02 07:57:23 -07:00
kprobes.c [PATCH] kretprobe spinlock deadlock patch 2006-10-02 07:57:16 -07:00
ksysfs.c
kthread.c [PATCH] remove kernel/kthread.c:kthread_stop_sem() 2006-07-14 21:53:52 -07:00
latency.c [PATCH] maximum latency tracking infrastructure 2006-10-01 00:39:19 -07:00
lockdep.c [PATCH] namespaces: utsname: use init_utsname when appropriate 2006-10-02 07:57:21 -07:00
lockdep_internals.h [PATCH] lockdep: double the number of stack-trace entries 2006-09-13 07:32:14 -07:00
lockdep_proc.c [PATCH] lockdep: procfs 2006-07-03 15:27:04 -07:00
module.c [PATCH] Create kallsyms_lookup_size_offset() 2006-10-03 08:03:41 -07:00
mutex-debug.c [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
mutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
mutex.c [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
mutex.h [PATCH] lockdep: prove mutex locking correctness 2006-07-03 15:27:04 -07:00
nsproxy.c [PATCH] nsproxy cloning error path fix 2006-10-02 07:57:22 -07:00
panic.c [PATCH] x86: Clean up x86 NMI sysctls 2006-09-30 01:47:55 +02:00
params.c [PATCH] module_subsys: initialize earlier 2006-09-29 09:18:08 -07:00
pid.c [PATCH] introduce get_task_pid() to fix unsafe get_pid() 2006-10-02 07:57:25 -07:00
posix-cpu-timers.c [PATCH] posix-timers: Fix the flags handling in posix_cpu_nsleep() 2006-09-29 09:18:15 -07:00
posix-timers.c fix file specification in comments 2006-10-03 23:01:26 +02:00
printk.c [PATCH] PM: make it possible to disable console suspending 2006-09-26 08:49:03 -07:00
profile.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
ptrace.c [PATCH] pidspace: is_init() 2006-09-29 09:18:12 -07:00
rcupdate.c [PATCH] rcu: simplify/improve batch tuning 2006-10-04 07:55:31 -07:00
rcutorture.c [PATCH] rcu: add sched torture type to rcutorture 2006-10-04 07:55:31 -07:00
relay.c [PATCH] kernel-doc for relay interface 2006-09-29 09:18:06 -07:00
resource.c [PATCH] kernel-doc for kernel/resource.c 2006-10-03 08:03:41 -07:00
rtmutex-debug.c Remove all inclusions of <linux/config.h> 2006-10-04 03:38:54 -04:00
rtmutex-debug.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex-tester.c Remove all inclusions of <linux/config.h> 2006-10-04 03:38:54 -04:00
rtmutex.c [PATCH] clean up and remove some extra spinlocks from rtmutex 2006-09-29 09:18:09 -07:00
rtmutex.h [PATCH] lockdep: better lock debugging 2006-07-03 15:27:01 -07:00
rtmutex_common.h
rwsem.c [PATCH] lockdep: prove rwsem locking correctness 2006-07-03 15:27:04 -07:00
sched.c [PATCH] scheduler: NUMA aware placement of sched_group_allnodes 2006-10-03 08:04:07 -07:00
seccomp.c
signal.c [PATCH] usb: fixup usb so it uses struct pid 2006-10-02 07:57:15 -07:00
softirq.c [PATCH] check return value of cpu_callback 2006-09-29 09:18:14 -07:00
softlockup.c [PATCH] check return value of cpu_callback 2006-09-29 09:18:14 -07:00
spinlock.c [PATCH] Directed yield: cpu_relax variants for spinlocks and rw-locks 2006-10-01 00:39:21 -07:00
srcu.c [PATCH] SRCU: report out-of-memory errors 2006-10-04 07:55:30 -07:00
stacktrace.c [PATCH] lockdep: stacktrace subsystem, core 2006-07-03 15:27:02 -07:00
stop_machine.c [PATCH] stop_machine.c copyright 2006-09-29 09:18:24 -07:00
sys.c [PATCH] SRCU: report out-of-memory errors 2006-10-04 07:55:30 -07:00
sys_ni.c [PATCH] BLOCK: Make it possible to disable the block layer [try #6] 2006-09-30 20:52:31 +02:00
sysctl.c [PATCH] replace cad_pid by a struct pid 2006-10-02 07:57:25 -07:00
taskstats.c [PATCH] csa: Extended system accounting over taskstats 2006-10-01 00:39:29 -07:00
time.c [PATCH] NTP: Move all the NTP related code to ntp.c 2006-10-01 00:39:26 -07:00
timer.c [PATCH] kill wall_jiffies 2006-10-01 00:39:27 -07:00
tsacct.c [PATCH] csa accounting taskstats update 2006-10-01 00:39:29 -07:00
uid16.c
unwind.c [PATCH] unwind: fix unused variable warning when !CONFIG_MODULES 2006-09-29 09:18:11 -07:00
user.c
utsname.c [PATCH] namespaces: utsname: implement CLONE_NEWUTS flag 2006-10-02 07:57:22 -07:00
wait.c [PATCH] uninline init_waitqueue_head() 2006-07-10 13:24:25 -07:00
workqueue.c remove duplicate "until" from kernel/workqueue.c 2006-10-03 23:07:31 +02:00