patch-2.0.19 linux/include/asm-i386/semaphore.h

• Lines: 66
• Date: Wed Sep 11 13:17:14 1996
• Orig file: v2.0.18/linux/include/asm-i386/semaphore.h
• Orig date: Thu Jan 1 02:00:00 1970

diff -u --recursive --new-file v2.0.18/linux/include/asm-i386/semaphore.h linux/include/asm-i386/semaphore.h
@@ -0,0 +1,65 @@
+#ifndef _I386_SEMAPHORE_H
+#define _I386_SEMAPHORE_H
+
+/*
+ * SMP- and interrupt-safe semaphores..
+ *
+ * (C) Copyright 1996 Linus Torvalds
+ */
+
+struct semaphore {
+	int count;
+	int waiting;
+	struct wait_queue * wait;
+};
+
+#define MUTEX ((struct semaphore) { 1, 0, NULL })
+#define MUTEX_LOCKED ((struct semaphore) { 0, 0, NULL })
+
+extern void __down(struct semaphore * sem);
+extern void wake_up(struct wait_queue ** p);
+
+/*
+ * This is ugly, but we want the default case to fall through.
+ * "down_failed" is a special asm handler that calls the C
+ * routine that actually waits. See arch/i386/lib/semaphore.S
+ */
+extern inline void down(struct semaphore * sem)
+{
+	__asm__ __volatile__(
+		"# atomic down operation\n"
+		"1:\n\t"
+		"leal 1b,%%eax\n\t"
+#ifdef __SMP__
+		"lock ; "
+#endif
+		"decl %0\n\t"
+		"js down_failed"
+		:/* no outputs */
+		:"m" (sem->count), "c" (sem)
+		:"ax","dx","memory");
+}
+
+/*
+ * Note! This is subtle. We jump to wake people up only if
+ * the semaphore was negative (== somebody was waiting on it).
+ * The default case (no contention) will result in NO
+ * jumps for both down() and up().
+ */
+extern inline void up(struct semaphore * sem)
+{
+	__asm__ __volatile__(
+		"# atomic up operation\n\t"
+		"leal 1f,%%eax\n\t"
+#ifdef __SMP__
+		"lock ; "
+#endif
+		"incl %0\n\t"
+		"jle up_wakeup\n"
+		"1:"
+		:/* no outputs */
+		:"m" (sem->count), "c" (sem)
+		:"ax", "dx", "memory");
+}
+
+#endif