![David Howells](/assets/img/avatar_default.png)
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)
211 lines
4.8 KiB
C
211 lines
4.8 KiB
C
/*
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* linux/kernel/irq/spurious.c
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*
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* Copyright (C) 1992, 1998-2004 Linus Torvalds, Ingo Molnar
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*
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* This file contains spurious interrupt handling.
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*/
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#include <linux/irq.h>
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#include <linux/module.h>
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#include <linux/kallsyms.h>
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#include <linux/interrupt.h>
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static int irqfixup __read_mostly;
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/*
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* Recovery handler for misrouted interrupts.
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*/
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static int misrouted_irq(int irq)
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{
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int i;
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int ok = 0;
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int work = 0; /* Did we do work for a real IRQ */
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for (i = 1; i < NR_IRQS; i++) {
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struct irq_desc *desc = irq_desc + i;
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struct irqaction *action;
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if (i == irq) /* Already tried */
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continue;
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spin_lock(&desc->lock);
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/* Already running on another processor */
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if (desc->status & IRQ_INPROGRESS) {
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/*
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* Already running: If it is shared get the other
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* CPU to go looking for our mystery interrupt too
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*/
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if (desc->action && (desc->action->flags & IRQF_SHARED))
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desc->status |= IRQ_PENDING;
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spin_unlock(&desc->lock);
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continue;
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}
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/* Honour the normal IRQ locking */
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desc->status |= IRQ_INPROGRESS;
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action = desc->action;
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spin_unlock(&desc->lock);
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while (action) {
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/* Only shared IRQ handlers are safe to call */
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if (action->flags & IRQF_SHARED) {
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if (action->handler(i, action->dev_id) ==
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IRQ_HANDLED)
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ok = 1;
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}
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action = action->next;
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}
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local_irq_disable();
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/* Now clean up the flags */
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spin_lock(&desc->lock);
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action = desc->action;
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/*
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* While we were looking for a fixup someone queued a real
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* IRQ clashing with our walk:
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*/
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while ((desc->status & IRQ_PENDING) && action) {
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/*
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* Perform real IRQ processing for the IRQ we deferred
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*/
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work = 1;
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spin_unlock(&desc->lock);
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handle_IRQ_event(i, action);
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spin_lock(&desc->lock);
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desc->status &= ~IRQ_PENDING;
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}
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desc->status &= ~IRQ_INPROGRESS;
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/*
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* If we did actual work for the real IRQ line we must let the
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* IRQ controller clean up too
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*/
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if (work && desc->chip && desc->chip->end)
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desc->chip->end(i);
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spin_unlock(&desc->lock);
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}
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/* So the caller can adjust the irq error counts */
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return ok;
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}
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/*
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* If 99,900 of the previous 100,000 interrupts have not been handled
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* then assume that the IRQ is stuck in some manner. Drop a diagnostic
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* and try to turn the IRQ off.
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*
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* (The other 100-of-100,000 interrupts may have been a correctly
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* functioning device sharing an IRQ with the failing one)
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*
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* Called under desc->lock
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*/
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static void
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__report_bad_irq(unsigned int irq, struct irq_desc *desc,
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irqreturn_t action_ret)
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{
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struct irqaction *action;
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if (action_ret != IRQ_HANDLED && action_ret != IRQ_NONE) {
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printk(KERN_ERR "irq event %d: bogus return value %x\n",
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irq, action_ret);
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} else {
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printk(KERN_ERR "irq %d: nobody cared (try booting with "
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"the \"irqpoll\" option)\n", irq);
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}
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dump_stack();
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printk(KERN_ERR "handlers:\n");
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action = desc->action;
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while (action) {
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printk(KERN_ERR "[<%p>]", action->handler);
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print_symbol(" (%s)",
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(unsigned long)action->handler);
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printk("\n");
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action = action->next;
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}
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}
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static void
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report_bad_irq(unsigned int irq, struct irq_desc *desc, irqreturn_t action_ret)
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{
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static int count = 100;
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if (count > 0) {
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count--;
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__report_bad_irq(irq, desc, action_ret);
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}
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}
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void note_interrupt(unsigned int irq, struct irq_desc *desc,
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irqreturn_t action_ret)
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{
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if (unlikely(action_ret != IRQ_HANDLED)) {
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desc->irqs_unhandled++;
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if (unlikely(action_ret != IRQ_NONE))
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report_bad_irq(irq, desc, action_ret);
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}
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if (unlikely(irqfixup)) {
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/* Don't punish working computers */
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if ((irqfixup == 2 && irq == 0) || action_ret == IRQ_NONE) {
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int ok = misrouted_irq(irq);
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if (action_ret == IRQ_NONE)
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desc->irqs_unhandled -= ok;
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}
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}
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desc->irq_count++;
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if (likely(desc->irq_count < 100000))
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return;
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desc->irq_count = 0;
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if (unlikely(desc->irqs_unhandled > 99900)) {
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/*
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* The interrupt is stuck
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*/
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__report_bad_irq(irq, desc, action_ret);
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/*
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* Now kill the IRQ
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*/
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printk(KERN_EMERG "Disabling IRQ #%d\n", irq);
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desc->status |= IRQ_DISABLED;
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desc->depth = 1;
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desc->chip->disable(irq);
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}
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desc->irqs_unhandled = 0;
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}
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int noirqdebug __read_mostly;
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int __init noirqdebug_setup(char *str)
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{
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noirqdebug = 1;
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printk(KERN_INFO "IRQ lockup detection disabled\n");
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return 1;
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}
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__setup("noirqdebug", noirqdebug_setup);
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static int __init irqfixup_setup(char *str)
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{
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irqfixup = 1;
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printk(KERN_WARNING "Misrouted IRQ fixup support enabled.\n");
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printk(KERN_WARNING "This may impact system performance.\n");
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return 1;
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}
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__setup("irqfixup", irqfixup_setup);
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static int __init irqpoll_setup(char *str)
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{
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irqfixup = 2;
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printk(KERN_WARNING "Misrouted IRQ fixup and polling support "
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"enabled\n");
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printk(KERN_WARNING "This may significantly impact system "
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"performance\n");
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return 1;
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}
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__setup("irqpoll", irqpoll_setup);
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