irq.c

讲述linux的初始化过程

		if (!--count) {
			show("wait_on_bh");
			count = ~0;
		}
		/* nothing .. wait for the other bh's to go away */
	} while (atomic_read(&global_bh_count) != 0);
}


static inline void wait_on_irq(int cpu)
{
	int count = MAXCOUNT;

	for (;;) {

		/*
		 * Wait until all interrupts are gone. Wait
		 * for bottom half handlers unless we're
		 * already executing in one..
		 */
		if (!atomic_read(&global_irq_count)) {
			if (local_bh_count(cpu)
			    || !atomic_read(&global_bh_count))
				break;
		}

		/* Duh, we have to loop. Release the lock to avoid deadlocks */
		clear_bit(0,&global_irq_lock);

		for (;;) {
			if (!--count) {
				show("wait_on_irq");
				count = ~0;
			}
			__sti();
			/* don't worry about the lock race Linus found
			 * on intel here. -- Cort
			 */
			__cli();
			if (atomic_read(&global_irq_count))
				continue;
			if (global_irq_lock)
				continue;
			if (!local_bh_count(cpu)
			    && atomic_read(&global_bh_count))
				continue;
			if (!test_and_set_bit(0,&global_irq_lock))
				break;
		}
	}
}

/*
 * This is called when we want to synchronize with
 * bottom half handlers. We need to wait until
 * no other CPU is executing any bottom half handler.
 *
 * Don't wait if we're already running in an interrupt
 * context or are inside a bh handler.
 */
void synchronize_bh(void)
{
	if (atomic_read(&global_bh_count) && !in_interrupt())
		wait_on_bh();
}

/*
 * This is called when we want to synchronize with
 * interrupts. We may for example tell a device to
 * stop sending interrupts: but to make sure there
 * are no interrupts that are executing on another
 * CPU we need to call this function.
 */
void synchronize_irq(void)
{
	if (atomic_read(&global_irq_count)) {
		/* Stupid approach */
		cli();
		sti();
	}
}

static inline void get_irqlock(int cpu)
{
	unsigned int loops = MAXCOUNT;

	if (test_and_set_bit(0,&global_irq_lock)) {
		/* do we already hold the lock? */
		if ((unsigned char) cpu == global_irq_holder)
			return;
		/* Uhhuh.. Somebody else got it. Wait.. */
		do {
			do {
				if (loops-- == 0) {
					printk("get_irqlock(%d) waiting, global_irq_holder=%d\n", cpu, global_irq_holder);
#ifdef CONFIG_XMON
					xmon(0);
#endif
				}
			} while (test_bit(0,&global_irq_lock));
		} while (test_and_set_bit(0,&global_irq_lock));		
	}
	/* 
	 * We also need to make sure that nobody else is running
	 * in an interrupt context. 
	 */
	wait_on_irq(cpu);

	/*
	 * Ok, finally..
	 */
	global_irq_holder = cpu;
}

/*
 * A global "cli()" while in an interrupt context
 * turns into just a local cli(). Interrupts
 * should use spinlocks for the (very unlikely)
 * case that they ever want to protect against
 * each other.
 *
 * If we already have local interrupts disabled,
 * this will not turn a local disable into a
 * global one (problems with spinlocks: this makes
 * save_flags+cli+sti usable inside a spinlock).
 */
void __global_cli(void)
{
	unsigned long flags;
	
	__save_flags(flags);
	if (flags & (1 << 15)) {
		int cpu = smp_processor_id();
		__cli();
		if (!local_irq_count(cpu))
			get_irqlock(cpu);
	}
}

void __global_sti(void)
{
	int cpu = smp_processor_id();

	if (!local_irq_count(cpu))
		release_irqlock(cpu);
	__sti();
}

/*
 * SMP flags value to restore to:
 * 0 - global cli
 * 1 - global sti
 * 2 - local cli
 * 3 - local sti
 */
unsigned long __global_save_flags(void)
{
	int retval;
	int local_enabled;
	unsigned long flags;

	__save_flags(flags);
	local_enabled = (flags >> 15) & 1;
	/* default to local */
	retval = 2 + local_enabled;

	/* check for global flags if we're not in an interrupt */
	if (!local_irq_count(smp_processor_id())) {
		if (local_enabled)
			retval = 1;
		if (global_irq_holder == (unsigned char) smp_processor_id())
			retval = 0;
	}
	return retval;
}

int
tb(long vals[],
   int  max_size)
{
   register unsigned long *orig_sp __asm__ ("r1");
   register unsigned long lr __asm__ ("r3");
   unsigned long *sp;
   int i;

   asm volatile ("mflr 3");
   vals[0] = lr;
   sp = (unsigned long *) *orig_sp;
   sp = (unsigned long *) *sp;
   for (i=1; i<max_size; i++) {
      if (sp == 0) {
         break;
      }

      vals[i] = *(sp+1);
      sp = (unsigned long *) *sp;
   }

   return i;
}

void __global_restore_flags(unsigned long flags)
{
	switch (flags) {
	case 0:
		__global_cli();
		break;
	case 1:
		__global_sti();
		break;
	case 2:
		__cli();
		break;
	case 3:
		__sti();
		break;
	default:
	{
		unsigned long trace[5];
                int           count;
                int           i;

		printk("global_restore_flags: %08lx (%08lx)\n",
			flags, (&flags)[-1]);
                count = tb(trace, 5);
                printk("tb:");
                for(i=0; i<count; i++) {
			printk(" %8.8lx", trace[i]);
		}
		printk("\n");
	}
	}
}
#endif /* CONFIG_SMP */

static struct proc_dir_entry * root_irq_dir;
static struct proc_dir_entry * irq_dir [NR_IRQS];
static struct proc_dir_entry * smp_affinity_entry [NR_IRQS];

unsigned int irq_affinity [NR_IRQS] = { [0 ... NR_IRQS-1] = 0xffffffff};

#define HEX_DIGITS 8

static int irq_affinity_read_proc (char *page, char **start, off_t off,
			int count, int *eof, void *data)
{
	if (count < HEX_DIGITS+1)
		return -EINVAL;
	return sprintf (page, "%08x\n", irq_affinity[(int)data]);
}

static unsigned int parse_hex_value (const char *buffer,
		unsigned long count, unsigned long *ret)
{
	unsigned char hexnum [HEX_DIGITS];
	unsigned long value;
	int i;

	if (!count)
		return -EINVAL;
	if (count > HEX_DIGITS)
		count = HEX_DIGITS;
	if (copy_from_user(hexnum, buffer, count))
		return -EFAULT;

	/*
	 * Parse the first 8 characters as a hex string, any non-hex char
	 * is end-of-string. '00e1', 'e1', '00E1', 'E1' are all the same.
	 */
	value = 0;

	for (i = 0; i < count; i++) {
		unsigned int c = hexnum[i];

		switch (c) {
			case '0' ... '9': c -= '0'; break;
			case 'a' ... 'f': c -= 'a'-10; break;
			case 'A' ... 'F': c -= 'A'-10; break;
		default:
			goto out;
		}
		value = (value << 4) | c;
	}
out:
	*ret = value;
	return 0;
}

static int irq_affinity_write_proc (struct file *file, const char *buffer,
					unsigned long count, void *data)
{
	int irq = (int) data, full_count = count, err;
	unsigned long new_value;

	if (!irq_desc[irq].handler->set_affinity)
		return -EIO;

	err = parse_hex_value(buffer, count, &new_value);

#if 0/*CONFIG_SMP*/
	/*
	 * Do not allow disabling IRQs completely - it's a too easy
	 * way to make the system unusable accidentally :-) At least
	 * one online CPU still has to be targeted.
	 */
	if (!(new_value & cpu_online_map))
		return -EINVAL;
#endif

	irq_affinity[irq] = new_value;
	irq_desc[irq].handler->set_affinity(irq, new_value);

	return full_count;
}

static int prof_cpu_mask_read_proc (char *page, char **start, off_t off,
			int count, int *eof, void *data)
{
	unsigned long *mask = (unsigned long *) data;
	if (count < HEX_DIGITS+1)
		return -EINVAL;
	return sprintf (page, "%08lx\n", *mask);
}

static int prof_cpu_mask_write_proc (struct file *file, const char *buffer,
					unsigned long count, void *data)
{
	unsigned long *mask = (unsigned long *) data, full_count = count, err;
	unsigned long new_value;

	err = parse_hex_value(buffer, count, &new_value);
	if (err)
		return err;

	*mask = new_value;
	return full_count;
}

#define MAX_NAMELEN 10

static void register_irq_proc (unsigned int irq)
{
	struct proc_dir_entry *entry;
	char name [MAX_NAMELEN];

	if (!root_irq_dir || (irq_desc[irq].handler == NULL))
		return;

	memset(name, 0, MAX_NAMELEN);
	sprintf(name, "%d", irq);

	/* create /proc/irq/1234 */
	irq_dir[irq] = proc_mkdir(name, root_irq_dir);

	/* create /proc/irq/1234/smp_affinity */
	entry = create_proc_entry("smp_affinity", 0600, irq_dir[irq]);

	entry->nlink = 1;
	entry->data = (void *)irq;
	entry->read_proc = irq_affinity_read_proc;
	entry->write_proc = irq_affinity_write_proc;

	smp_affinity_entry[irq] = entry;
}

unsigned long prof_cpu_mask = -1;

void init_irq_proc (void)
{
	struct proc_dir_entry *entry;
	int i;

	/* create /proc/irq */
	root_irq_dir = proc_mkdir("irq", 0);

	/* create /proc/irq/prof_cpu_mask */
	entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);

	entry->nlink = 1;
	entry->data = (void *)&prof_cpu_mask;
	entry->read_proc = prof_cpu_mask_read_proc;
	entry->write_proc = prof_cpu_mask_write_proc;

	/*
	 * Create entries for all existing IRQs.
	 */
	for (i = 0; i < NR_IRQS; i++) {
		if (irq_desc[i].handler == NULL)
			continue;
		register_irq_proc(i);
	}
}

void no_action(int irq, void *dev, struct pt_regs *regs)
{
}