patch-2.3.48 linux/include/asm-mips64/semaphore.h

• Lines: 348
• Date: Thu Feb 24 22:53:35 2000
• Orig file: v2.3.47/linux/include/asm-mips64/semaphore.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.47/linux/include/asm-mips64/semaphore.h linux/include/asm-mips64/semaphore.h
@@ -0,0 +1,347 @@
+/* $Id: semaphore.h,v 1.6 2000/02/24 03:09:52 ulfc Exp $
+ *
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 1996  Linus Torvalds
+ * Copyright (C) 1998, 1999, 2000  Ralf Baechle
+ * Copyright (C) 1999, 2000  Silicon Graphics, Inc.
+ */
+#ifndef _ASM_SEMAPHORE_H
+#define _ASM_SEMAPHORE_H
+
+#include <asm/system.h>
+#include <asm/atomic.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
+
+struct semaphore {
+#ifdef __MIPSEB__
+	atomic_t count;
+	atomic_t waking;
+#else
+	atomic_t waking;
+	atomic_t count;
+#endif
+	wait_queue_head_t wait;
+#if WAITQUEUE_DEBUG
+	long __magic;
+#endif
+};
+
+#if WAITQUEUE_DEBUG
+# define __SEM_DEBUG_INIT(name) \
+		, (long)&(name).__magic
+#else
+# define __SEM_DEBUG_INIT(name)
+#endif
+
+#ifdef __MIPSEB__
+#define __SEMAPHORE_INITIALIZER(name,count) \
+{ ATOMIC_INIT(count), ATOMIC_INIT(0), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
+	__SEM_DEBUG_INIT(name) }
+#else
+#define __SEMAPHORE_INITIALIZER(name,count) \
+{ ATOMIC_INIT(0), ATOMIC_INIT(count), __WAIT_QUEUE_HEAD_INITIALIZER((name).wait) \
+	__SEM_DEBUG_INIT(name) }
+#endif
+
+#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)
+
+extern inline void sema_init (struct semaphore *sem, int val)
+{
+	atomic_set(&sem->count, val);
+	atomic_set(&sem->waking, 0);
+	init_waitqueue_head(&sem->wait);
+#if WAITQUEUE_DEBUG
+	sem->__magic = (long)&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(struct semaphore * sem);
+asmlinkage int  __down_interruptible(struct semaphore * sem);
+asmlinkage int __down_trylock(struct semaphore * sem);
+asmlinkage void __up(struct semaphore * sem);
+
+extern inline void down(struct semaphore * sem)
+{
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+	if (atomic_dec_return(&sem->count) < 0)
+		__down(sem);
+}
+
+extern inline int down_interruptible(struct semaphore * sem)
+{
+	int ret = 0;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+	if (atomic_dec_return(&sem->count) < 0)
+		ret = __down_interruptible(sem);
+	return ret;
+}
+
+/*
+ * down_trylock returns 0 on success, 1 if we failed to get the lock.
+ *
+ * We must manipulate count and waking simultaneously and atomically.
+ * Here, we this by using ll/sc on the pair of 32-bit words.
+ *
+ * Pseudocode:
+ *
+ *   Decrement(sem->count)
+ *   If(sem->count >=0) {
+ *	Return(SUCCESS)			// resource is free
+ *   } else {
+ *	If(sem->waking <= 0) {		// if no wakeup pending
+ *	   Increment(sem->count)	// undo decrement
+ *	   Return(FAILURE)
+ *      } else {
+ *	   Decrement(sem->waking)	// otherwise "steal" wakeup
+ *	   Return(SUCCESS)
+ *	}
+ *   }
+ */
+extern inline int down_trylock(struct semaphore * sem)
+{
+	long ret, tmp, tmp2, sub;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	__asm__ __volatile__("
+			.set	mips3
+
+		0:	lld	%1, %4
+			dli	%3, 0x0000000100000000
+			dsubu	%1, %3
+			li	%0, 0
+			bgez	%1, 2f
+			sll	%2, %1, 0
+			blez	%2, 1f
+			daddiu	%1, %1, -1
+			b	2f
+		1:
+			daddu	%1, %1, %3
+			li	%0, 1
+		2:
+			scd	%1, %4
+			beqz	%1, 0b
+
+			.set	mips0"
+		: "=&r"(ret), "=&r"(tmp), "=&r"(tmp2), "=&r"(sub)
+		: "m"(*sem)
+		: "memory");
+
+	return ret;
+}
+
+/*
+ * Note! This is subtle. We jump to wake people up only if
+ * the semaphore was negative (== somebody was waiting on it).
+ */
+extern inline void up(struct semaphore * sem)
+{
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+	if (atomic_inc_return(&sem->count) <= 0)
+		__up(sem);
+}
+
+/*
+ * rw mutexes (should that be mutices? =) -- throw rw spinlocks and
+ * semaphores together, and this is what we end up with...
+ *
+ * The lock is initialized to BIAS.  This way, a writer subtracts BIAS ands
+ * gets 0 for the case of an uncontended lock.  Readers decrement by 1 and
+ * see a positive value when uncontended, negative if there are writers
+ * waiting (in which case it goes to sleep).
+ *
+ * The value 0x01000000 supports up to 128 processors and lots of processes.
+ * BIAS must be chosen such that subtracting BIAS once per CPU will result
+ * in the int remaining negative.  In terms of fairness, this should result
+ * in the lock flopping back and forth between readers and writers under
+ * heavy use.
+ *
+ * Once we start supporting machines with more than 128 CPUs, we should go
+ * for using a 64bit atomic type instead of 32bit as counter. We shall
+ * probably go for bias 0x80000000 then, so that single sethi can set it.
+ * */
+
+#define RW_LOCK_BIAS		0x01000000
+
+struct rw_semaphore {
+	atomic_t		count;
+	/* bit 0 means read bias granted;
+	   bit 1 means write bias granted.  */
+	unsigned		granted;
+	wait_queue_head_t	wait;
+	wait_queue_head_t	write_bias_wait;
+#if WAITQUEUE_DEBUG
+	long			__magic;
+	atomic_t		readers;
+	atomic_t		writers;
+#endif
+};
+
+#if WAITQUEUE_DEBUG
+#define __RWSEM_DEBUG_INIT	, ATOMIC_INIT(0), ATOMIC_INIT(0)
+#else
+#define __RWSEM_DEBUG_INIT	/* */
+#endif
+
+#define __RWSEM_INITIALIZER(name,count)					\
+	{ ATOMIC_INIT(count), 0,					\
+	  __WAIT_QUEUE_HEAD_INITIALIZER((name).wait),			\
+	  __WAIT_QUEUE_HEAD_INITIALIZER((name).write_bias_wait)		\
+	  __SEM_DEBUG_INIT(name) __RWSEM_DEBUG_INIT }
+
+#define __DECLARE_RWSEM_GENERIC(name,count) \
+	struct rw_semaphore name = __RWSEM_INITIALIZER(name,count)
+
+#define DECLARE_RWSEM(name) \
+	__DECLARE_RWSEM_GENERIC(name, RW_LOCK_BIAS)
+#define DECLARE_RWSEM_READ_LOCKED(name) \
+	__DECLARE_RWSEM_GENERIC(name, RW_LOCK_BIAS-1)
+#define DECLARE_RWSEM_WRITE_LOCKED(name) \
+	__DECLARE_RWSEM_GENERIC(name, 0)
+
+extern inline void init_rwsem(struct rw_semaphore *sem)
+{
+	atomic_set(&sem->count, RW_LOCK_BIAS);
+	sem->granted = 0;
+	init_waitqueue_head(&sem->wait);
+	init_waitqueue_head(&sem->write_bias_wait);
+#if WAITQUEUE_DEBUG
+	sem->__magic = (long)&sem->__magic;
+	atomic_set(&sem->readers, 0);
+	atomic_set(&sem->writers, 0);
+#endif
+}
+
+/* The expensive part is outlined.  */
+extern void __down_read(struct rw_semaphore *sem, int count);
+extern void __down_write(struct rw_semaphore *sem, int count);
+extern void __rwsem_wake(struct rw_semaphore *sem, unsigned long readers);
+
+extern inline void down_read(struct rw_semaphore *sem)
+{
+	int count;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	count = atomic_dec_return(&sem->count);
+	if (count < 0) {
+		__down_read(sem, count);
+	}
+	mb();
+
+#if WAITQUEUE_DEBUG
+	if (sem->granted & 2)
+		BUG();
+	if (atomic_read(&sem->writers))
+		BUG();
+	atomic_inc(&sem->readers);
+#endif
+}
+
+extern inline void down_write(struct rw_semaphore *sem)
+{
+	int count;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	count = atomic_sub_return(RW_LOCK_BIAS, &sem->count);
+	if (count) {
+		__down_write(sem, count);
+	}
+	mb();
+
+#if WAITQUEUE_DEBUG
+	if (atomic_read(&sem->writers))
+		BUG();
+	if (atomic_read(&sem->readers))
+		BUG();
+	if (sem->granted & 3)
+		BUG();
+	atomic_inc(&sem->writers);
+#endif
+}
+
+/* When a reader does a release, the only significant case is when
+   there was a writer waiting, and we've bumped the count to 0: we must
+   wake the writer up.  */
+
+extern inline void up_read(struct rw_semaphore *sem)
+{
+	int count;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+	if (sem->granted & 2)
+		BUG();
+	if (atomic_read(&sem->writers))
+		BUG();
+	atomic_dec(&sem->readers);
+#endif
+
+	mb();
+	count = atomic_inc_return(&sem->count);
+	if (count == 0) {
+		__rwsem_wake(sem, 0);
+	}
+}
+
+/*
+ * Releasing the writer is easy -- just release it and wake up any sleepers.
+ */
+extern inline void up_write(struct rw_semaphore *sem)
+{
+	int count;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+	if (sem->granted & 3)
+		BUG();
+	if (atomic_read(&sem->readers))
+		BUG();
+	if (atomic_read(&sem->writers) != 1)
+		BUG();
+	atomic_dec(&sem->writers);
+#endif
+
+	mb();
+	count = atomic_add_return(RW_LOCK_BIAS, &sem->count);
+	if (count - RW_LOCK_BIAS < 0 && count >= 0) {
+		/* Only do the wake if we're no longer negative.  */
+		__rwsem_wake(sem, count);
+	}
+}
+
+#endif /* _ASM_SEMAPHORE_H */