patch-2.4.20 linux-2.4.20/arch/parisc/kernel/irq_smp.c

• Lines: 233
• Date: Thu Nov 28 15:53:10 2002
• Orig file: linux-2.4.19/arch/parisc/kernel/irq_smp.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/arch/parisc/kernel/irq_smp.c linux-2.4.20/arch/parisc/kernel/irq_smp.c
@@ -0,0 +1,232 @@
+/*
+ *  linux/arch/parisc/kernel/irq_smp.c
+ *  (90% stolen from alpha port, 9% from ia64, rest is mine -ggg)
+ *  
+ *  Copyright (C) 2001 Hewlett-Packard Co
+ *  Copyright (C) 2001 Grant Grundler <grundler@puffin.external.hp.com>
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/signal.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/random.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/irq.h>
+
+#include <asm/system.h>
+#include <asm/io.h>
+
+
+int global_irq_holder = NO_PROC_ID;	/* Who has global_irq_lock. */
+spinlock_t global_irq_lock = SPIN_LOCK_UNLOCKED; /* protects IRQ's. */
+
+
+/* Global IRQ locking depth. */
+static void *previous_irqholder = NULL;
+
+#define MAXCOUNT 100000000
+
+
+static void
+show(char * str, void *where)
+{
+	int cpu = smp_processor_id();
+
+	printk("\n%s, CPU %d: %p\n", str, cpu, where);
+	printk("irq:  %d [%d %d]\n",
+		irqs_running(),
+		local_irq_count(0),
+		local_irq_count(1));
+
+	printk("bh:   %d [%d %d]\n",
+		spin_is_locked(&global_bh_lock) ? 1 : 0,
+		local_bh_count(0),
+		local_bh_count(1));
+}
+
+static inline void
+wait_on_irq(int cpu, void *where)
+{
+	int count = MAXCOUNT;
+
+	for (;;) {
+
+		/*
+		 * Wait until all interrupts are gone. Wait
+		 * for bottom half handlers unless we're
+		 * already executing in one..
+		 */
+		if (!irqs_running()) {
+			if (local_bh_count(cpu)
+			    || !spin_is_locked(&global_bh_lock))
+				break;
+		}
+
+		/* Duh, we have to loop. Release the lock to avoid deadlocks */
+		spin_unlock(&global_irq_lock);
+
+		for (;;) {
+			if (!--count) {
+				show("wait_on_irq", where);
+				count = MAXCOUNT;
+			}
+			__sti();
+			udelay(1); /* make sure to run pending irqs */
+			__cli();
+
+			if (irqs_running())
+				continue;
+			if (spin_is_locked(&global_irq_lock))
+				continue;
+			if (!local_bh_count(cpu)
+			    && spin_is_locked(&global_bh_lock))
+				continue;
+			if (spin_trylock(&global_irq_lock))
+				break;
+		}
+	}
+}
+
+static inline void
+get_irqlock(int cpu, void* where)
+{
+	if (!spin_trylock(&global_irq_lock)) {
+		/* Do we already hold the lock?  */
+		if (cpu == global_irq_holder)
+			return;
+		/* Uhhuh.. Somebody else got it.  Wait.  */
+		spin_lock(&global_irq_lock);
+	}
+
+	/*
+	 * Ok, we got the lock bit.
+	 * But that's actually just the easy part.. Now
+	 * we need to make sure that nobody else is running
+	 * in an interrupt context. 
+	 */
+	wait_on_irq(cpu, where);
+
+	/*
+	 * Finally.
+	 */
+#if DEBUG_SPINLOCK
+	global_irq_lock.task = current;
+	global_irq_lock.previous = where;
+#endif
+	global_irq_holder = cpu;
+	previous_irqholder = where;
+}
+
+
+/*
+** 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 int flags;
+	__save_flags(flags);
+	if (flags & PSW_I) {
+		int cpu = smp_processor_id();
+		__cli(); 
+		if (!local_irq_count(cpu)) {
+			void *where = __builtin_return_address(0);
+			get_irqlock(cpu, where);
+		}
+	}
+}
+
+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;
+	int cpu = smp_processor_id();
+
+	__save_flags(flags);
+	local_enabled = (flags & PSW_I) != 0;
+	/* default to local */
+	retval = 2 + local_enabled;
+
+	/* Check for global flags if we're not in an interrupt.  */
+	if (!local_irq_count(cpu)) {
+		if (local_enabled)
+			retval = 1;
+		if (global_irq_holder == cpu)
+			retval = 0;
+	}
+	return retval;
+}
+
+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:
+		printk(KERN_ERR "global_restore_flags: %08lx (%p)\n",
+			flags, __builtin_return_address(0));
+	}
+}
+
+/*
+ * From its use, I infer that synchronize_irq() stalls a thread until
+ * the effects of a command to an external device are known to have
+ * taken hold.  Typically, the command is to stop sending interrupts.
+ * The strategy here is wait until there is at most one processor
+ * (this one) in an irq.  The memory barrier serializes the write to
+ * the device and the subsequent accesses of global_irq_count.
+ * --jmartin
+ */
+#define DEBUG_SYNCHRONIZE_IRQ 0
+
+void
+synchronize_irq(void)
+{
+	/* Jay's version.  */
+	if (irqs_running()) {
+		cli();
+		sti();
+	}
+}