patch-2.4.20 linux-2.4.20/include/asm-x86_64/spinlock.h

• Lines: 183
• Date: Thu Nov 28 15:53:15 2002
• Orig file: linux-2.4.19/include/asm-x86_64/spinlock.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/include/asm-x86_64/spinlock.h linux-2.4.20/include/asm-x86_64/spinlock.h
@@ -0,0 +1,182 @@
+#ifndef __ASM_SPINLOCK_H
+#define __ASM_SPINLOCK_H
+
+#include <asm/atomic.h>
+#include <asm/rwlock.h>
+#include <asm/page.h>
+#include <linux/kernel.h>
+#include <linux/config.h>
+
+extern int printk(const char * fmt, ...)
+	__attribute__ ((format (printf, 1, 2)));
+
+/* It seems that people are forgetting to
+ * initialize their spinlocks properly, tsk tsk.
+ * Remember to turn this off in 2.4. -ben
+ */
+#if defined(CONFIG_DEBUG_SPINLOCK)
+#define SPINLOCK_DEBUG	1
+#else
+#define SPINLOCK_DEBUG	0
+#endif
+
+/*
+ * Your basic SMP spinlocks, allowing only a single CPU anywhere
+ */
+
+typedef struct {
+	volatile unsigned int lock;
+#if SPINLOCK_DEBUG
+	unsigned magic;
+#endif
+} spinlock_t;
+
+#define SPINLOCK_MAGIC	0xdead4ead
+
+#if SPINLOCK_DEBUG
+#define SPINLOCK_MAGIC_INIT	, SPINLOCK_MAGIC
+#else
+#define SPINLOCK_MAGIC_INIT	/* */
+#endif
+
+#define SPIN_LOCK_UNLOCKED (spinlock_t) { 1 SPINLOCK_MAGIC_INIT }
+
+#define spin_lock_init(x)	do { *(x) = SPIN_LOCK_UNLOCKED; } while(0)
+
+/*
+ * Simple spin lock operations.  There are two variants, one clears IRQ's
+ * on the local processor, one does not.
+ *
+ * We make no fairness assumptions. They have a cost.
+ */
+
+#define spin_is_locked(x)	(*(volatile signed char *)(&(x)->lock) <= 0)
+#define spin_unlock_wait(x)	do { barrier(); } while(spin_is_locked(x))
+
+#define spin_lock_string \
+	"\n1:\t" \
+	"lock ; decb %0\n\t" \
+	"js 2f\n" \
+	".section .text.lock,\"ax\"\n" \
+	"2:\t" \
+	"cmpb $0,%0\n\t" \
+	"rep;nop\n\t" \
+	"jle 2b\n\t" \
+	"jmp 1b\n" \
+	".previous"
+
+/*
+ * This works. Despite all the confusion.
+ */
+#define spin_unlock_string \
+	"movb $1,%0"
+
+static inline int spin_trylock(spinlock_t *lock)
+{
+	char oldval;
+	__asm__ __volatile__(
+		"xchgb %b0,%1"
+		:"=q" (oldval), "=m" (lock->lock)
+		:"0" (0) : "memory");
+	return oldval > 0;
+}
+
+static inline void spin_lock(spinlock_t *lock)
+{
+#if SPINLOCK_DEBUG
+	__label__ here;
+here:
+	if (lock->magic != SPINLOCK_MAGIC) {
+printk("eip: %p\n", &&here);
+		out_of_line_bug();
+	}
+#endif
+	__asm__ __volatile__(
+		spin_lock_string
+		:"=m" (lock->lock) : : "memory");
+}
+
+static inline void spin_unlock(spinlock_t *lock)
+{
+#if SPINLOCK_DEBUG
+	if (lock->magic != SPINLOCK_MAGIC)
+		out_of_line_bug();
+	if (!spin_is_locked(lock))
+		out_of_line_bug();
+#endif
+	__asm__ __volatile__(
+		spin_unlock_string
+		:"=m" (lock->lock) : : "memory");
+}
+
+/*
+ * Read-write spinlocks, allowing multiple readers
+ * but only one writer.
+ *
+ * NOTE! it is quite common to have readers in interrupts
+ * but no interrupt writers. For those circumstances we
+ * can "mix" irq-safe locks - any writer needs to get a
+ * irq-safe write-lock, but readers can get non-irqsafe
+ * read-locks.
+ */
+typedef struct {
+	volatile unsigned int lock;
+#if SPINLOCK_DEBUG
+	unsigned magic;
+#endif
+} rwlock_t;
+
+#define RWLOCK_MAGIC	0xdeaf1eed
+
+#if SPINLOCK_DEBUG
+#define RWLOCK_MAGIC_INIT	, RWLOCK_MAGIC
+#else
+#define RWLOCK_MAGIC_INIT	/* */
+#endif
+
+#define RW_LOCK_UNLOCKED (rwlock_t) { RW_LOCK_BIAS RWLOCK_MAGIC_INIT }
+
+#define rwlock_init(x)	do { *(x) = RW_LOCK_UNLOCKED; } while(0)
+
+/*
+ * On x86, we implement read-write locks as a 32-bit counter
+ * with the high bit (sign) being the "contended" bit.
+ *
+ * The inline assembly is non-obvious. Think about it.
+ *
+ * Changed to use the same technique as rw semaphores.  See
+ * semaphore.h for details.  -ben
+ */
+/* the spinlock helpers are in arch/x86_64/kernel/semaphore.S */
+
+extern inline void read_lock(rwlock_t *rw)
+{
+#if SPINLOCK_DEBUG
+	if (rw->magic != RWLOCK_MAGIC)
+		out_of_line_bug();
+#endif
+	__build_read_lock(rw, "__read_lock_failed");
+}
+
+static inline void write_lock(rwlock_t *rw)
+{
+#if SPINLOCK_DEBUG
+	if (rw->magic != RWLOCK_MAGIC)
+		out_of_line_bug();
+#endif
+	__build_write_lock(rw, "__write_lock_failed");
+}
+
+#define read_unlock(rw)		asm volatile("lock ; incl %0" :"=m" ((rw)->lock) : : "memory")
+#define write_unlock(rw)	asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0":"=m" ((rw)->lock) : : "memory")
+
+static inline int write_trylock(rwlock_t *lock)
+{
+	atomic_t *count = (atomic_t *)lock;
+	if (atomic_sub_and_test(RW_LOCK_BIAS, count))
+		return 1;
+	atomic_add(RW_LOCK_BIAS, count);
+	return 0;
+}
+
+#endif /* __ASM_SPINLOCK_H */