[mirror_ubuntu-jammy-kernel.git] / arch / x86 / kernel / irq_32.c

/*
 *	Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
 *
 * This file contains the lowest level x86-specific interrupt
 * entry, irq-stacks and irq statistics code. All the remaining
 * irq logic is done by the generic kernel/irq/ code and
 * by the x86-specific irq controller code. (e.g. i8259.c and
 * io_apic.c.)
 */

#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/delay.h>

#include <asm/apic.h>
#include <asm/uaccess.h>

DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
EXPORT_PER_CPU_SYMBOL(irq_stat);

DEFINE_PER_CPU(struct pt_regs *, irq_regs);
EXPORT_PER_CPU_SYMBOL(irq_regs);

/*
 * 'what should we do if we get a hw irq event on an illegal vector'.
 * each architecture has to answer this themselves.
 */
void ack_bad_irq(unsigned int irq)
{
	printk(KERN_ERR "unexpected IRQ trap at vector %02x\n", irq);

#ifdef CONFIG_X86_LOCAL_APIC
	/*
	 * Currently unexpected vectors happen only on SMP and APIC.
	 * We _must_ ack these because every local APIC has only N
	 * irq slots per priority level, and a 'hanging, unacked' IRQ
	 * holds up an irq slot - in excessive cases (when multiple
	 * unexpected vectors occur) that might lock up the APIC
	 * completely.
	 * But only ack when the APIC is enabled -AK
	 */
	if (cpu_has_apic)
		ack_APIC_irq();
#endif
}

#ifdef CONFIG_4KSTACKS
/*
 * per-CPU IRQ handling contexts (thread information and stack)
 */
union irq_ctx {
	struct thread_info      tinfo;
	u32                     stack[THREAD_SIZE/sizeof(u32)];
};

static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
#endif

/*
 * do_IRQ handles all normal device IRQ's (the special
 * SMP cross-CPU interrupts have their own specific
 * handlers).
 */
fastcall unsigned int do_IRQ(struct pt_regs *regs)
{	
	struct pt_regs *old_regs;
	/* high bit used in ret_from_ code */
	int irq = ~regs->orig_eax;
	struct irq_desc *desc = irq_desc + irq;
#ifdef CONFIG_4KSTACKS
	union irq_ctx *curctx, *irqctx;
	u32 *isp;
#endif

	if (unlikely((unsigned)irq >= NR_IRQS)) {
		printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
					__FUNCTION__, irq);
		BUG();
	}

	old_regs = set_irq_regs(regs);
	irq_enter();
#ifdef CONFIG_DEBUG_STACKOVERFLOW
	/* Debugging check for stack overflow: is there less than 1KB free? */
	{
		long esp;

		__asm__ __volatile__("andl %%esp,%0" :
					"=r" (esp) : "0" (THREAD_SIZE - 1));
		if (unlikely(esp < (sizeof(struct thread_info) + STACK_WARN))) {
			printk("do_IRQ: stack overflow: %ld\n",
				esp - sizeof(struct thread_info));
			dump_stack();
		}
	}
#endif

#ifdef CONFIG_4KSTACKS

	curctx = (union irq_ctx *) current_thread_info();
	irqctx = hardirq_ctx[smp_processor_id()];

	/*
	 * this is where we switch to the IRQ stack. However, if we are
	 * already using the IRQ stack (because we interrupted a hardirq
	 * handler) we can't do that and just have to keep using the
	 * current stack (which is the irq stack already after all)
	 */
	if (curctx != irqctx) {
		int arg1, arg2, ebx;

		/* build the stack frame on the IRQ stack */
		isp = (u32*) ((char*)irqctx + sizeof(*irqctx));
		irqctx->tinfo.task = curctx->tinfo.task;
		irqctx->tinfo.previous_esp = current_stack_pointer;

		/*
		 * Copy the softirq bits in preempt_count so that the
		 * softirq checks work in the hardirq context.
		 */
		irqctx->tinfo.preempt_count =
			(irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) |
			(curctx->tinfo.preempt_count & SOFTIRQ_MASK);

		asm volatile(
			"       xchgl  %%ebx,%%esp      \n"
			"       call   *%%edi           \n"
			"       movl   %%ebx,%%esp      \n"
			: "=a" (arg1), "=d" (arg2), "=b" (ebx)
			:  "0" (irq),   "1" (desc),  "2" (isp),
			   "D" (desc->handle_irq)
			: "memory", "cc"
		);
	} else
#endif
		desc->handle_irq(irq, desc);

	irq_exit();
	set_irq_regs(old_regs);
	return 1;
}

#ifdef CONFIG_4KSTACKS

static char softirq_stack[NR_CPUS * THREAD_SIZE]
		__attribute__((__section__(".bss.page_aligned")));

static char hardirq_stack[NR_CPUS * THREAD_SIZE]
		__attribute__((__section__(".bss.page_aligned")));

/*
 * allocate per-cpu stacks for hardirq and for softirq processing
 */
void irq_ctx_init(int cpu)
{
	union irq_ctx *irqctx;

	if (hardirq_ctx[cpu])
		return;

	irqctx = (union irq_ctx*) &hardirq_stack[cpu*THREAD_SIZE];
	irqctx->tinfo.task              = NULL;
	irqctx->tinfo.exec_domain       = NULL;
	irqctx->tinfo.cpu               = cpu;
	irqctx->tinfo.preempt_count     = HARDIRQ_OFFSET;
	irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);

	hardirq_ctx[cpu] = irqctx;

	irqctx = (union irq_ctx*) &softirq_stack[cpu*THREAD_SIZE];
	irqctx->tinfo.task              = NULL;
	irqctx->tinfo.exec_domain       = NULL;
	irqctx->tinfo.cpu               = cpu;
	irqctx->tinfo.preempt_count     = 0;
	irqctx->tinfo.addr_limit        = MAKE_MM_SEG(0);

	softirq_ctx[cpu] = irqctx;

	printk("CPU %u irqstacks, hard=%p soft=%p\n",
		cpu,hardirq_ctx[cpu],softirq_ctx[cpu]);
}

void irq_ctx_exit(int cpu)
{
	hardirq_ctx[cpu] = NULL;
}

extern asmlinkage void __do_softirq(void);

asmlinkage void do_softirq(void)
{
	unsigned long flags;
	struct thread_info *curctx;
	union irq_ctx *irqctx;
	u32 *isp;

	if (in_interrupt())
		return;

	local_irq_save(flags);

	if (local_softirq_pending()) {
		curctx = current_thread_info();
		irqctx = softirq_ctx[smp_processor_id()];
		irqctx->tinfo.task = curctx->task;
		irqctx->tinfo.previous_esp = current_stack_pointer;

		/* build the stack frame on the softirq stack */
		isp = (u32*) ((char*)irqctx + sizeof(*irqctx));

		asm volatile(
			"       xchgl   %%ebx,%%esp     \n"
			"       call    __do_softirq    \n"
			"       movl    %%ebx,%%esp     \n"
			: "=b"(isp)
			: "0"(isp)
			: "memory", "cc", "edx", "ecx", "eax"
		);
		/*
		 * Shouldnt happen, we returned above if in_interrupt():
	 	 */
		WARN_ON_ONCE(softirq_count());
	}

	local_irq_restore(flags);
}
#endif

/*
 * Interrupt statistics:
 */

atomic_t irq_err_count;

/*
 * /proc/interrupts printing:
 */

int show_interrupts(struct seq_file *p, void *v)
{
	int i = *(loff_t *) v, j;
	struct irqaction * action;
	unsigned long flags;

	if (i == 0) {
		seq_printf(p, "           ");
		for_each_online_cpu(j)
			seq_printf(p, "CPU%-8d",j);
		seq_putc(p, '\n');
	}

	if (i < NR_IRQS) {
		spin_lock_irqsave(&irq_desc[i].lock, flags);
		action = irq_desc[i].action;
		if (!action)
			goto skip;
		seq_printf(p, "%3d: ",i);
#ifndef CONFIG_SMP
		seq_printf(p, "%10u ", kstat_irqs(i));
#else
		for_each_online_cpu(j)
			seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
#endif
		seq_printf(p, " %8s", irq_desc[i].chip->name);
		seq_printf(p, "-%-8s", irq_desc[i].name);
		seq_printf(p, "  %s", action->name);

		for (action=action->next; action; action = action->next)
			seq_printf(p, ", %s", action->name);

		seq_putc(p, '\n');
skip:
		spin_unlock_irqrestore(&irq_desc[i].lock, flags);
	} else if (i == NR_IRQS) {
		seq_printf(p, "NMI: ");
		for_each_online_cpu(j)
			seq_printf(p, "%10u ", nmi_count(j));
		seq_putc(p, '\n');
#ifdef CONFIG_X86_LOCAL_APIC
		seq_printf(p, "LOC: ");
		for_each_online_cpu(j)
			seq_printf(p, "%10u ",
				per_cpu(irq_stat,j).apic_timer_irqs);
		seq_putc(p, '\n');
#endif
		seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
#if defined(CONFIG_X86_IO_APIC)
		seq_printf(p, "MIS: %10u\n", atomic_read(&irq_mis_count));
#endif
	}
	return 0;
}

#ifdef CONFIG_HOTPLUG_CPU
#include <mach_apic.h>

void fixup_irqs(cpumask_t map)
{
	unsigned int irq;
	static int warned;

	for (irq = 0; irq < NR_IRQS; irq++) {
		cpumask_t mask;
		if (irq == 2)
			continue;

		cpus_and(mask, irq_desc[irq].affinity, map);
		if (any_online_cpu(mask) == NR_CPUS) {
			printk("Breaking affinity for irq %i\n", irq);
			mask = map;
		}
		if (irq_desc[irq].chip->set_affinity)
			irq_desc[irq].chip->set_affinity(irq, mask);
		else if (irq_desc[irq].action && !(warned++))
			printk("Cannot set affinity for irq %i\n", irq);
	}

#if 0
	barrier();
	/* Ingo Molnar says: "after the IO-APIC masks have been redirected
	   [note the nop - the interrupt-enable boundary on x86 is two
	   instructions from sti] - to flush out pending hardirqs and
	   IPIs. After this point nothing is supposed to reach this CPU." */
	__asm__ __volatile__("sti; nop; cli");
	barrier();
#else
	/* That doesn't seem sufficient.  Give it 1ms. */
	local_irq_enable();
	mdelay(1);
	local_irq_disable();
#endif
}
#endif
Commit	Line	Data
1da177e4	1	/*
1da177e4 LT	2	* Copyright (C) 1992, 1998 Linus Torvalds, Ingo Molnar
	3	*
	4	* This file contains the lowest level x86-specific interrupt
	5	* entry, irq-stacks and irq statistics code. All the remaining
	6	* irq logic is done by the generic kernel/irq/ code and
	7	* by the x86-specific irq controller code. (e.g. i8259.c and
	8	* io_apic.c.)
	9	*/
	10
1da177e4 LT	11	#include <linux/module.h>
	12	#include <linux/seq_file.h>
	13	#include <linux/interrupt.h>
	14	#include <linux/kernel_stat.h>
f3705136 ZM	15	#include <linux/notifier.h>
	16	#include <linux/cpu.h>
	17	#include <linux/delay.h>
1da177e4	18
e05d723f TG	19	#include <asm/apic.h>
	20	#include <asm/uaccess.h>
	21
f34e3b61	22	DEFINE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
1da177e4 LT	23	EXPORT_PER_CPU_SYMBOL(irq_stat);
1da177e4 LT	24
7c3576d2 JF	25	DEFINE_PER_CPU(struct pt_regs *, irq_regs);
	26	EXPORT_PER_CPU_SYMBOL(irq_regs);
	27
1da177e4 LT	28	/*
	29	* 'what should we do if we get a hw irq event on an illegal vector'.
	30	* each architecture has to answer this themselves.
	31	*/
	32	void ack_bad_irq(unsigned int irq)
	33	{
e05d723f TG	34	printk(KERN_ERR "unexpected IRQ trap at vector %02x\n", irq);
	35
	36	#ifdef CONFIG_X86_LOCAL_APIC
	37	/*
	38	* Currently unexpected vectors happen only on SMP and APIC.
	39	* We _must_ ack these because every local APIC has only N
	40	* irq slots per priority level, and a 'hanging, unacked' IRQ
	41	* holds up an irq slot - in excessive cases (when multiple
	42	* unexpected vectors occur) that might lock up the APIC
	43	* completely.
	44	* But only ack when the APIC is enabled -AK
	45	*/
	46	if (cpu_has_apic)
	47	ack_APIC_irq();
1da177e4	48	#endif
e05d723f	49	}
1da177e4 LT	50
	51	#ifdef CONFIG_4KSTACKS
	52	/*
	53	* per-CPU IRQ handling contexts (thread information and stack)
	54	*/
	55	union irq_ctx {
	56	struct thread_info tinfo;
	57	u32 stack[THREAD_SIZE/sizeof(u32)];
	58	};
	59
22722051 AM	60	static union irq_ctx *hardirq_ctx[NR_CPUS] __read_mostly;
22722051 AM	61	static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
1da177e4 LT	62	#endif
	63
	64	/*
	65	* do_IRQ handles all normal device IRQ's (the special
	66	* SMP cross-CPU interrupts have their own specific
	67	* handlers).
	68	*/
	69	fastcall unsigned int do_IRQ(struct pt_regs *regs)
	70	{
7d12e780	71	struct pt_regs *old_regs;
19eadf98 RR	72	/* high bit used in ret_from_ code */
19eadf98 RR	73	int irq = ~regs->orig_eax;
f5b9ed7a	74	struct irq_desc *desc = irq_desc + irq;
1da177e4 LT	75	#ifdef CONFIG_4KSTACKS
	76	union irq_ctx curctx, irqctx;
	77	u32 *isp;
	78	#endif
	79
a052b68b AM	80	if (unlikely((unsigned)irq >= NR_IRQS)) {
	81	printk(KERN_EMERG "%s: cannot handle IRQ %d\n",
	82	__FUNCTION__, irq);
	83	BUG();
	84	}
	85
7d12e780	86	old_regs = set_irq_regs(regs);
1da177e4 LT	87	irq_enter();
	88	#ifdef CONFIG_DEBUG_STACKOVERFLOW
	89	/* Debugging check for stack overflow: is there less than 1KB free? */
	90	{
	91	long esp;
	92
	93	__asm__ __volatile__("andl %%esp,%0" :
	94	"=r" (esp) : "0" (THREAD_SIZE - 1));
	95	if (unlikely(esp < (sizeof(struct thread_info) + STACK_WARN))) {
	96	printk("do_IRQ: stack overflow: %ld\n",
	97	esp - sizeof(struct thread_info));
	98	dump_stack();
	99	}
	100	}
	101	#endif
	102
	103	#ifdef CONFIG_4KSTACKS
	104
	105	curctx = (union irq_ctx *) current_thread_info();
	106	irqctx = hardirq_ctx[smp_processor_id()];
	107
	108	/*
	109	* this is where we switch to the IRQ stack. However, if we are
	110	* already using the IRQ stack (because we interrupted a hardirq
	111	* handler) we can't do that and just have to keep using the
	112	* current stack (which is the irq stack already after all)
	113	*/
	114	if (curctx != irqctx) {
7d12e780	115	int arg1, arg2, ebx;
1da177e4 LT	116
	117	/* build the stack frame on the IRQ stack */
	118	isp = (u32) ((char)irqctx + sizeof(*irqctx));
	119	irqctx->tinfo.task = curctx->tinfo.task;
	120	irqctx->tinfo.previous_esp = current_stack_pointer;
	121
a5d157e0 BS	122	/*
	123	* Copy the softirq bits in preempt_count so that the
	124	* softirq checks work in the hardirq context.
	125	*/
	126	irqctx->tinfo.preempt_count =
91bf4602 AM	127	(irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) \|
91bf4602 AM	128	(curctx->tinfo.preempt_count & SOFTIRQ_MASK);
a5d157e0	129
1da177e4	130	asm volatile(
f5b9ed7a IM	131	" xchgl %%ebx,%%esp \n"
f5b9ed7a IM	132	" call *%%edi \n"
1da177e4	133	" movl %%ebx,%%esp \n"
7d12e780 DH	134	: "=a" (arg1), "=d" (arg2), "=b" (ebx)
7d12e780 DH	135	: "0" (irq), "1" (desc), "2" (isp),
f5b9ed7a IM	136	"D" (desc->handle_irq)
f5b9ed7a IM	137	: "memory", "cc"
1da177e4 LT	138	);
	139	} else
	140	#endif
7d12e780	141	desc->handle_irq(irq, desc);
1da177e4 LT	142
1da177e4 LT	143	irq_exit();
7d12e780	144	set_irq_regs(old_regs);
1da177e4 LT	145	return 1;
	146	}
	147
	148	#ifdef CONFIG_4KSTACKS
	149
1da177e4	150	static char softirq_stack[NR_CPUS * THREAD_SIZE]
09fce8a1	151	__attribute__((__section__(".bss.page_aligned")));
1da177e4 LT	152
1da177e4 LT	153	static char hardirq_stack[NR_CPUS * THREAD_SIZE]
09fce8a1	154	__attribute__((__section__(".bss.page_aligned")));
1da177e4 LT	155
	156	/*
	157	* allocate per-cpu stacks for hardirq and for softirq processing
	158	*/
	159	void irq_ctx_init(int cpu)
	160	{
	161	union irq_ctx *irqctx;
	162
	163	if (hardirq_ctx[cpu])
	164	return;
	165
	166	irqctx = (union irq_ctx) &hardirq_stack[cpuTHREAD_SIZE];
	167	irqctx->tinfo.task = NULL;
	168	irqctx->tinfo.exec_domain = NULL;
	169	irqctx->tinfo.cpu = cpu;
	170	irqctx->tinfo.preempt_count = HARDIRQ_OFFSET;
	171	irqctx->tinfo.addr_limit = MAKE_MM_SEG(0);
	172
	173	hardirq_ctx[cpu] = irqctx;
	174
	175	irqctx = (union irq_ctx) &softirq_stack[cpuTHREAD_SIZE];
	176	irqctx->tinfo.task = NULL;
	177	irqctx->tinfo.exec_domain = NULL;
	178	irqctx->tinfo.cpu = cpu;
55f327fa	179	irqctx->tinfo.preempt_count = 0;
1da177e4 LT	180	irqctx->tinfo.addr_limit = MAKE_MM_SEG(0);
	181
	182	softirq_ctx[cpu] = irqctx;
	183
	184	printk("CPU %u irqstacks, hard=%p soft=%p\n",
	185	cpu,hardirq_ctx[cpu],softirq_ctx[cpu]);
	186	}
	187
e1367daf LS	188	void irq_ctx_exit(int cpu)
	189	{
	190	hardirq_ctx[cpu] = NULL;
	191	}
	192
1da177e4 LT	193	extern asmlinkage void __do_softirq(void);
	194
	195	asmlinkage void do_softirq(void)
	196	{
	197	unsigned long flags;
	198	struct thread_info *curctx;
	199	union irq_ctx *irqctx;
	200	u32 *isp;
	201
	202	if (in_interrupt())
	203	return;
	204
	205	local_irq_save(flags);
	206
	207	if (local_softirq_pending()) {
	208	curctx = current_thread_info();
	209	irqctx = softirq_ctx[smp_processor_id()];
	210	irqctx->tinfo.task = curctx->task;
	211	irqctx->tinfo.previous_esp = current_stack_pointer;
	212
	213	/* build the stack frame on the softirq stack */
	214	isp = (u32) ((char)irqctx + sizeof(*irqctx));
	215
	216	asm volatile(
	217	" xchgl %%ebx,%%esp \n"
	218	" call __do_softirq \n"
	219	" movl %%ebx,%%esp \n"
	220	: "=b"(isp)
	221	: "0"(isp)
	222	: "memory", "cc", "edx", "ecx", "eax"
	223	);
55f327fa IM	224	/*
	225	* Shouldnt happen, we returned above if in_interrupt():
	226	*/
	227	WARN_ON_ONCE(softirq_count());
1da177e4 LT	228	}
	229
	230	local_irq_restore(flags);
	231	}
1da177e4 LT	232	#endif
	233
	234	/*
	235	* Interrupt statistics:
	236	*/
	237
	238	atomic_t irq_err_count;
	239
	240	/*
	241	* /proc/interrupts printing:
	242	*/
	243
	244	int show_interrupts(struct seq_file p, void v)
	245	{
	246	int i = (loff_t ) v, j;
	247	struct irqaction * action;
	248	unsigned long flags;
	249
	250	if (i == 0) {
	251	seq_printf(p, " ");
9f40a72a	252	for_each_online_cpu(j)
bdbdaa79	253	seq_printf(p, "CPU%-8d",j);
1da177e4 LT	254	seq_putc(p, '\n');
	255	}
	256
	257	if (i < NR_IRQS) {
	258	spin_lock_irqsave(&irq_desc[i].lock, flags);
	259	action = irq_desc[i].action;
	260	if (!action)
	261	goto skip;
	262	seq_printf(p, "%3d: ",i);
	263	#ifndef CONFIG_SMP
	264	seq_printf(p, "%10u ", kstat_irqs(i));
	265	#else
9f40a72a	266	for_each_online_cpu(j)
f3705136	267	seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
1da177e4	268	#endif
f5b9ed7a	269	seq_printf(p, " %8s", irq_desc[i].chip->name);
a460e745	270	seq_printf(p, "-%-8s", irq_desc[i].name);
1da177e4 LT	271	seq_printf(p, " %s", action->name);
	272
	273	for (action=action->next; action; action = action->next)
	274	seq_printf(p, ", %s", action->name);
	275
	276	seq_putc(p, '\n');
	277	skip:
	278	spin_unlock_irqrestore(&irq_desc[i].lock, flags);
	279	} else if (i == NR_IRQS) {
	280	seq_printf(p, "NMI: ");
9f40a72a	281	for_each_online_cpu(j)
f3705136	282	seq_printf(p, "%10u ", nmi_count(j));
1da177e4 LT	283	seq_putc(p, '\n');
	284	#ifdef CONFIG_X86_LOCAL_APIC
	285	seq_printf(p, "LOC: ");
9f40a72a	286	for_each_online_cpu(j)
f3705136 ZM	287	seq_printf(p, "%10u ",
f3705136 ZM	288	per_cpu(irq_stat,j).apic_timer_irqs);
1da177e4 LT	289	seq_putc(p, '\n');
	290	#endif
	291	seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
	292	#if defined(CONFIG_X86_IO_APIC)
	293	seq_printf(p, "MIS: %10u\n", atomic_read(&irq_mis_count));
	294	#endif
	295	}
	296	return 0;
	297	}
f3705136 ZM	298
	299	#ifdef CONFIG_HOTPLUG_CPU
	300	#include <mach_apic.h>
	301
	302	void fixup_irqs(cpumask_t map)
	303	{
	304	unsigned int irq;
	305	static int warned;
	306
	307	for (irq = 0; irq < NR_IRQS; irq++) {
	308	cpumask_t mask;
	309	if (irq == 2)
	310	continue;
	311
a53da52f	312	cpus_and(mask, irq_desc[irq].affinity, map);
f3705136 ZM	313	if (any_online_cpu(mask) == NR_CPUS) {
	314	printk("Breaking affinity for irq %i\n", irq);
	315	mask = map;
	316	}
d1bef4ed IM	317	if (irq_desc[irq].chip->set_affinity)
d1bef4ed IM	318	irq_desc[irq].chip->set_affinity(irq, mask);
f3705136 ZM	319	else if (irq_desc[irq].action && !(warned++))
	320	printk("Cannot set affinity for irq %i\n", irq);
	321	}
	322
	323	#if 0
	324	barrier();
	325	/* Ingo Molnar says: "after the IO-APIC masks have been redirected
	326	[note the nop - the interrupt-enable boundary on x86 is two
	327	instructions from sti] - to flush out pending hardirqs and
	328	IPIs. After this point nothing is supposed to reach this CPU." */
	329	__asm__ __volatile__("sti; nop; cli");
	330	barrier();
	331	#else
	332	/* That doesn't seem sufficient. Give it 1ms. */
	333	local_irq_enable();
	334	mdelay(1);
	335	local_irq_disable();
	336	#endif
	337	}
	338	#endif
	339