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

• Lines: 236
• Date: Thu Nov 28 15:53:15 2002
• Orig file: linux-2.4.19/include/asm-x86_64/semaphore.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -urN linux-2.4.19/include/asm-x86_64/semaphore.h linux-2.4.20/include/asm-x86_64/semaphore.h
@@ -0,0 +1,235 @@
+#ifndef _X86_64_SEMAPHORE_H
+#define _X86_64_SEMAPHORE_H
+
+#include <linux/linkage.h>
+
+#ifdef __KERNEL__
+
+/*
+ * SMP- and interrupt-safe semaphores..
+ *
+ * (C) Copyright 1996 Linus Torvalds
+ *
+ * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
+ *                     the original code and to make semaphore waits
+ *                     interruptible so that processes waiting on
+ *                     semaphores can be killed.
+ * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
+ *		       functions in asm/sempahore-helper.h while fixing a
+ *		       potential and subtle race discovered by Ulrich Schmid
+ *		       in down_interruptible(). Since I started to play here I
+ *		       also implemented the `trylock' semaphore operation.
+ *          1999-07-02 Artur Skawina <skawina@geocities.com>
+ *                     Optimized "0(ecx)" -> "(ecx)" (the assembler does not
+ *                     do this). Changed calling sequences from push/jmp to
+ *                     traditional call/ret.
+ * Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
+ *		       Some hacks to ensure compatibility with recent
+ *		       GCC snapshots, to avoid stack corruption when compiling
+ *		       with -fomit-frame-pointer. It's not sure if this will
+ *		       be fixed in GCC, as our previous implementation was a
+ *		       bit dubious.
+ *
+ * If you would like to see an analysis of this implementation, please
+ * ftp to gcom.com and download the file
+ * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
+ *
+ */
+
+#include <asm/system.h>
+#include <asm/atomic.h>
+#include <asm/rwlock.h>
+#include <linux/wait.h>
+#include <linux/rwsem.h>
+#include <linux/stringify.h>
+
+struct semaphore {
+	atomic_t count;
+	int sleepers;
+	wait_queue_head_t wait;
+#if WAITQUEUE_DEBUG
+	long __magic;
+#endif
+};
+
+#if WAITQUEUE_DEBUG
+# define __SEM_DEBUG_INIT(name) \
+		, (int)&(name).__magic
+#else
+# define __SEM_DEBUG_INIT(name)
+#endif
+
+#define __SEMAPHORE_INITIALIZER(name,count) \
+{ ATOMIC_INIT(count), 0, __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
+	__SEM_DEBUG_INIT(name) }
+
+#define __MUTEX_INITIALIZER(name) \
+	__SEMAPHORE_INITIALIZER(name,1)
+
+#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
+	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
+
+#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
+#define DECLARE_MUTEX_LOCKED(name) __DECLARE_SEMAPHORE_GENERIC(name,0)
+
+static inline void sema_init (struct semaphore *sem, int val)
+{
+/*
+ *	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
+ *
+ * i'd rather use the more flexible initialization above, but sadly
+ * GCC 2.7.2.3 emits a bogus warning. EGCS doesnt. Oh well.
+ */
+	atomic_set(&sem->count, val);
+	sem->sleepers = 0;
+	init_waitqueue_head(&sem->wait);
+#if WAITQUEUE_DEBUG
+	sem->__magic = (int)&sem->__magic;
+#endif
+}
+
+static inline void init_MUTEX (struct semaphore *sem)
+{
+	sema_init(sem, 1);
+}
+
+static inline void init_MUTEX_LOCKED (struct semaphore *sem)
+{
+	sema_init(sem, 0);
+}
+
+asmlinkage void __down_failed(void /* special register calling convention */);
+asmlinkage int  __down_failed_interruptible(void  /* params in registers */);
+asmlinkage int  __down_failed_trylock(void  /* params in registers */);
+asmlinkage void __up_wakeup(void /* special register calling convention */);
+
+asmlinkage void __down(struct semaphore * sem);
+asmlinkage int  __down_interruptible(struct semaphore * sem);
+asmlinkage int  __down_trylock(struct semaphore * sem);
+asmlinkage void __up(struct semaphore * sem);
+
+/*
+ * 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/x86_64/kernel/semaphore.c
+ */
+static inline void down(struct semaphore * sem)
+{
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	__asm__ __volatile__(
+		"# atomic down operation\n\t"
+		LOCK "decl %0\n\t"     /* --sem->count */
+		"js 2f\n"
+		"1:\n"
+                ".subsection 1\n" \
+                ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \
+                "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \
+                ".endif\n" \
+		"2:\tcall __down_failed\n\t"
+		"jmp 1b\n"
+		".subsection 0"
+		:"=m" (sem->count)
+		:"D" (sem)
+		:"memory");
+}
+
+/*
+ * Interruptible try to acquire a semaphore.  If we obtained
+ * it, return zero.  If we were interrupted, returns -EINTR
+ */
+static inline int down_interruptible(struct semaphore * sem)
+{
+	int result;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	__asm__ __volatile__(
+		"# atomic interruptible down operation\n\t"
+		LOCK "decl %1\n\t"     /* --sem->count */
+		"js 2f\n\t"
+		"xorl %0,%0\n"
+		"1:\n"
+                ".subsection 1\n" \
+               ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \
+                "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \
+                ".endif\n" \
+		"2:\tcall __down_failed_interruptible\n\t"
+		"jmp 1b\n"
+		".subsection 0"
+		:"=a" (result), "=m" (sem->count)
+		:"D" (sem)
+		:"memory");
+	return result;
+}
+
+/*
+ * Non-blockingly attempt to down() a semaphore.
+ * Returns zero if we acquired it
+ */
+static inline int down_trylock(struct semaphore * sem)
+{
+	int result;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	__asm__ __volatile__(
+		"# atomic interruptible down operation\n\t"
+		LOCK "decl %1\n\t"     /* --sem->count */
+		"js 2f\n\t"
+		"xorl %0,%0\n"
+		"1:\n"
+                ".subsection 1\n" \
+                ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \
+                "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \
+                ".endif\n" \
+		"2:\tcall __down_failed_trylock\n\t"
+		"jmp 1b\n"
+		".subsection 0"
+		:"=a" (result), "=m" (sem->count)
+		:"D" (sem)
+		:"memory","cc");
+	return result;
+}
+
+/*
+ * 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().
+ */
+static inline void up(struct semaphore * sem)
+{
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+	__asm__ __volatile__(
+		"# atomic up operation\n\t"
+		LOCK "incl %0\n\t"     /* ++sem->count */
+		"jle 2f\n"
+		"1:\n"
+                ".subsection 1\n" \
+                ".ifndef _text_lock_" __stringify(KBUILD_BASENAME) "\n" \
+                "_text_lock_" __stringify(KBUILD_BASENAME) ":\n" \
+                ".endif\n" \
+		"2:\tcall __up_wakeup\n\t"
+		"jmp 1b\n"
+		".subsection 0"
+		:"=m" (sem->count)
+		:"D" (sem)
+		:"memory");
+}
+
+static inline int sem_getcount(struct semaphore *sem)
+{
+       return atomic_read(&sem->count);
+}
+
+#endif /* __KERNEL__ */
+#endif