7d12e780e0
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)
87 lines
2.2 KiB
C
87 lines
2.2 KiB
C
/* defines for inline arch setup functions */
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#include <asm/apic.h>
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#include <asm/i8259.h>
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/**
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* do_timer_interrupt_hook - hook into timer tick
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* @regs: standard registers from interrupt
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*
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* Description:
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* This hook is called immediately after the timer interrupt is ack'd.
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* It's primary purpose is to allow architectures that don't possess
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* individual per CPU clocks (like the CPU APICs supply) to broadcast the
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* timer interrupt as a means of triggering reschedules etc.
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**/
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static inline void do_timer_interrupt_hook(void)
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{
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do_timer(1);
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#ifndef CONFIG_SMP
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update_process_times(user_mode_vm(get_irq_regs()));
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#endif
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/*
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* In the SMP case we use the local APIC timer interrupt to do the
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* profiling, except when we simulate SMP mode on a uniprocessor
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* system, in that case we have to call the local interrupt handler.
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*/
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#ifndef CONFIG_X86_LOCAL_APIC
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profile_tick(CPU_PROFILING);
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#else
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if (!using_apic_timer)
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smp_local_timer_interrupt();
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#endif
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}
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/* you can safely undefine this if you don't have the Neptune chipset */
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#define BUGGY_NEPTUN_TIMER
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/**
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* do_timer_overflow - process a detected timer overflow condition
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* @count: hardware timer interrupt count on overflow
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*
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* Description:
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* This call is invoked when the jiffies count has not incremented but
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* the hardware timer interrupt has. It means that a timer tick interrupt
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* came along while the previous one was pending, thus a tick was missed
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**/
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static inline int do_timer_overflow(int count)
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{
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int i;
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spin_lock(&i8259A_lock);
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/*
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* This is tricky when I/O APICs are used;
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* see do_timer_interrupt().
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*/
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i = inb(0x20);
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spin_unlock(&i8259A_lock);
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/* assumption about timer being IRQ0 */
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if (i & 0x01) {
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/*
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* We cannot detect lost timer interrupts ...
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* well, that's why we call them lost, don't we? :)
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* [hmm, on the Pentium and Alpha we can ... sort of]
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*/
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count -= LATCH;
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} else {
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#ifdef BUGGY_NEPTUN_TIMER
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/*
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* for the Neptun bug we know that the 'latch'
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* command doesn't latch the high and low value
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* of the counter atomically. Thus we have to
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* substract 256 from the counter
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* ... funny, isnt it? :)
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*/
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count -= 256;
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#else
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printk("do_slow_gettimeoffset(): hardware timer problem?\n");
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#endif
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}
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return count;
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}
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