smp.c

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/*
** SMP Support
**
** Copyright (C) 1999 Walt Drummond <[e-mail]>
** Copyright (C) 1999 David Mosberger-Tang <[e-mail]>
** Copyright (C) 2001,2004 Grant Grundler <[e-mail]>
** 
** Lots of stuff stolen from arch/alpha/kernel/smp.c
** ...and then parisc stole from arch/ia64/kernel/smp.c. Thanks David! :^)
**
** Thanks to John Curry and Ullas Ponnadi. I learned alot from their work.
** -grant (1/12/2001)
**
**	This program is free software; you can redistribute it and/or modify
**	it under the terms of the GNU General Public License as published by
**      the Free Software Foundation; either version 2 of the License, or
**      (at your option) any later version.
*/
#undef ENTRY_SYS_CPUS	/* syscall support for iCOD-like functionality */

#include <linux/autoconf.h>

#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/slab.h>

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/bitops.h>

#include <asm/system.h>
#include <asm/atomic.h>
#include <asm/current.h>
#include <asm/delay.h>
#include <asm/pgalloc.h>	/* for flush_tlb_all() proto/macro */

#include <asm/io.h>
#include <asm/irq.h>		/* for CPU_IRQ_REGION and friends */
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>

#define kDEBUG 0

DEFINE_SPINLOCK(smp_lock);

volatile struct task_struct *smp_init_current_idle_task;

static volatile int cpu_now_booting = 0;	/* track which CPU is booting */

static int parisc_max_cpus = 1;

/* online cpus are ones that we've managed to bring up completely
 * possible cpus are all valid cpu 
 * present cpus are all detected cpu
 *
 * On startup we bring up the "possible" cpus. Since we discover
 * CPUs later, we add them as hotplug, so the possible cpu mask is
 * empty in the beginning.
 */

cpumask_t cpu_online_map = CPU_MASK_NONE;	/* Bitmap of online CPUs */
cpumask_t cpu_possible_map = CPU_MASK_ALL;	/* Bitmap of Present CPUs */

EXPORT_SYMBOL(cpu_online_map);
EXPORT_SYMBOL(cpu_possible_map);


struct smp_call_struct {
	void (*func) (void *info);
	void *info;
	long wait;
	atomic_t unstarted_count;
	atomic_t unfinished_count;
};
static volatile struct smp_call_struct *smp_call_function_data;

enum ipi_message_type {
	IPI_NOP=0,
	IPI_RESCHEDULE=1,
	IPI_CALL_FUNC,
	IPI_CPU_START,
	IPI_CPU_STOP,
	IPI_CPU_TEST
};


/********** SMP inter processor interrupt and communication routines */

#undef PER_CPU_IRQ_REGION
#ifdef PER_CPU_IRQ_REGION
/* XXX REVISIT Ignore for now.
**    *May* need this "hook" to register IPI handler
**    once we have perCPU ExtIntr switch tables.
*/
static void
ipi_init(int cpuid)
{

	/* If CPU is present ... */
#ifdef ENTRY_SYS_CPUS
	/* *and* running (not stopped) ... */
#error iCOD support wants state checked here.
#endif

#error verify IRQ_OFFSET(IPI_IRQ) is ipi_interrupt() in new IRQ region

	if(cpu_online(cpuid) )
	{
		switch_to_idle_task(current);
	}

	return;
}
#endif


/*
** Yoink this CPU from the runnable list... 
**
*/
static void
halt_processor(void) 
{
#ifdef ENTRY_SYS_CPUS
#error halt_processor() needs rework
/*
** o migrate I/O interrupts off this CPU.
** o leave IPI enabled - __cli() will disable IPI.
** o leave CPU in online map - just change the state
*/
	cpu_data[this_cpu].state = STATE_STOPPED;
	mark_bh(IPI_BH);
#else
	/* REVISIT : redirect I/O Interrupts to another CPU? */
	/* REVISIT : does PM *know* this CPU isn't available? */
	cpu_clear(smp_processor_id(), cpu_online_map);
	local_irq_disable();
	for (;;)
		;
#endif
}


irqreturn_t
ipi_interrupt(int irq, void *dev_id, struct pt_regs *regs) 
{
	int this_cpu = smp_processor_id();
	struct cpuinfo_parisc *p = &cpu_data[this_cpu];
	unsigned long ops;
	unsigned long flags;

	/* Count this now; we may make a call that never returns. */
	p->ipi_count++;

	mb();	/* Order interrupt and bit testing. */

	for (;;) {
		spin_lock_irqsave(&(p->lock),flags);
		ops = p->pending_ipi;
		p->pending_ipi = 0;
		spin_unlock_irqrestore(&(p->lock),flags);

		mb(); /* Order bit clearing and data access. */

		if (!ops)
		    break;

		while (ops) {
			unsigned long which = ffz(~ops);

			switch (which) {
			case IPI_RESCHEDULE:
#if (kDEBUG>=100)
				printk(KERN_DEBUG "CPU%d IPI_RESCHEDULE\n",this_cpu);
#endif /* kDEBUG */
				ops &= ~(1 << IPI_RESCHEDULE);
				/*
				 * Reschedule callback.  Everything to be
				 * done is done by the interrupt return path.
				 */
				break;

			case IPI_CALL_FUNC:
#if (kDEBUG>=100)
				printk(KERN_DEBUG "CPU%d IPI_CALL_FUNC\n",this_cpu);
#endif /* kDEBUG */
				ops &= ~(1 << IPI_CALL_FUNC);
				{
					volatile struct smp_call_struct *data;
					void (*func)(void *info);
					void *info;
					int wait;

					data = smp_call_function_data;
					func = data->func;
					info = data->info;
					wait = data->wait;

					mb();
					atomic_dec ((atomic_t *)&data->unstarted_count);

					/* At this point, *data can't
					 * be relied upon.
					 */

					(*func)(info);

					/* Notify the sending CPU that the
					 * task is done.
					 */
					mb();
					if (wait)
						atomic_dec ((atomic_t *)&data->unfinished_count);
				}
				break;

			case IPI_CPU_START:
#if (kDEBUG>=100)
				printk(KERN_DEBUG "CPU%d IPI_CPU_START\n",this_cpu);
#endif /* kDEBUG */
				ops &= ~(1 << IPI_CPU_START);
#ifdef ENTRY_SYS_CPUS
				p->state = STATE_RUNNING;
#endif
				break;

			case IPI_CPU_STOP:
#if (kDEBUG>=100)
				printk(KERN_DEBUG "CPU%d IPI_CPU_STOP\n",this_cpu);
#endif /* kDEBUG */
				ops &= ~(1 << IPI_CPU_STOP);
#ifdef ENTRY_SYS_CPUS
#else
				halt_processor();
#endif
				break;

			case IPI_CPU_TEST:
#if (kDEBUG>=100)
				printk(KERN_DEBUG "CPU%d is alive!\n",this_cpu);
#endif /* kDEBUG */
				ops &= ~(1 << IPI_CPU_TEST);
				break;

			default:
				printk(KERN_CRIT "Unknown IPI num on CPU%d: %lu\n",
					this_cpu, which);
				ops &= ~(1 << which);
				return IRQ_NONE;
			} /* Switch */
		} /* while (ops) */
	}
	return IRQ_HANDLED;
}


static inline void
ipi_send(int cpu, enum ipi_message_type op)
{
	struct cpuinfo_parisc *p = &cpu_data[cpu];
	unsigned long flags;

	spin_lock_irqsave(&(p->lock),flags);
	p->pending_ipi |= 1 << op;
	gsc_writel(IPI_IRQ - CPU_IRQ_BASE, cpu_data[cpu].hpa);
	spin_unlock_irqrestore(&(p->lock),flags);
}


static inline void
send_IPI_single(int dest_cpu, enum ipi_message_type op)
{
	if (dest_cpu == NO_PROC_ID) {
		BUG();
		return;
	}

	ipi_send(dest_cpu, op);
}

static inline void
send_IPI_allbutself(enum ipi_message_type op)
{
	int i;
	
	for (i = 0; i < NR_CPUS; i++) {
		if (cpu_online(i) && i != smp_processor_id())
			send_IPI_single(i, op);
	}
}


inline void 
smp_send_stop(void)	{ send_IPI_allbutself(IPI_CPU_STOP); }

static inline void
smp_send_start(void)	{ send_IPI_allbutself(IPI_CPU_START); }

void 
smp_send_reschedule(int cpu) { send_IPI_single(cpu, IPI_RESCHEDULE); }


/**
 * Run a function on all other CPUs.
 *  <func>	The function to run. This must be fast and non-blocking.
 *  <info>	An arbitrary pointer to pass to the function.
 *  <retry>	If true, keep retrying until ready.
 *  <wait>	If true, wait until function has completed on other CPUs.
 *  [RETURNS]   0 on success, else a negative status code.
 *
 * Does not return until remote CPUs are nearly ready to execute <func>
 * or have executed.
 */

int
smp_call_function (void (*func) (void *info), void *info, int retry, int wait)
{
	struct smp_call_struct data;
	unsigned long timeout;
	static DEFINE_SPINLOCK(lock);
	int retries = 0;

	if (num_online_cpus() < 2)
		return 0;

	/* Can deadlock when called with interrupts disabled */
	WARN_ON(irqs_disabled());
	
	data.func = func;
	data.info = info;
	data.wait = wait;
	atomic_set(&data.unstarted_count, num_online_cpus() - 1);
	atomic_set(&data.unfinished_count, num_online_cpus() - 1);

	if (retry) {
		spin_lock (&lock);
		while (smp_call_function_data != 0)
			barrier();
	}
	else {
		spin_lock (&lock);
		if (smp_call_function_data) {
			spin_unlock (&lock);
			return -EBUSY;
		}
	}

	smp_call_function_data = &data;
	spin_unlock (&lock);