patch-2.4.2 linux/include/asm-cris/semaphore.h

• Lines: 322
• Date: Thu Feb 8 16:32:44 2001
• Orig file: v2.4.1/linux/include/asm-cris/semaphore.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.1/linux/include/asm-cris/semaphore.h linux/include/asm-cris/semaphore.h
@@ -0,0 +1,321 @@
+/* $Id: semaphore.h,v 1.2 2000/07/13 16:52:46 bjornw Exp $ */
+
+/* On the i386 these are coded in asm, perhaps we should as well. Later.. */
+
+#ifndef _CRIS_SEMAPHORE_H
+#define _CRIS_SEMAPHORE_H
+
+#define RW_LOCK_BIAS             0x01000000
+
+#include <linux/wait.h>
+#include <linux/spinlock.h>
+
+#include <asm/system.h>
+#include <asm/atomic.h>
+
+/*
+ * CRIS semaphores, implemented in C-only so far. 
+ */
+
+int printk(const char *fmt, ...);
+
+struct semaphore {
+	int count; /* not atomic_t since we do the atomicity here already */
+	atomic_t waking;
+	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
+
+#define __SEMAPHORE_INITIALIZER(name,count)             \
+        { count, ATOMIC_INIT(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)
+
+extern inline void sema_init(struct semaphore *sem, int val)
+{
+	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
+}
+
+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);
+}
+
+extern void __down(struct semaphore * sem);
+extern int __down_interruptible(struct semaphore * sem);
+extern int __down_trylock(struct semaphore * sem);
+extern void __up(struct semaphore * sem);
+
+/* notice - we probably can do cli/sti here instead of saving */
+
+extern inline void down(struct semaphore * sem)
+{
+	unsigned long flags;
+	int failed;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	/* atomically decrement the semaphores count, and if its negative, we wait */
+	save_flags(flags);
+	cli();
+	failed = --(sem->count) < 0;
+	restore_flags(flags);
+	if(failed) {
+		__down(sem);
+	}
+}
+
+/*
+ * This version waits in interruptible state so that the waiting
+ * process can be killed.  The down_interruptible routine
+ * returns negative for signalled and zero for semaphore acquired.
+ */
+
+extern inline int down_interruptible(struct semaphore * sem)
+{
+	unsigned long flags;
+	int failed;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	/* atomically decrement the semaphores count, and if its negative, we wait */
+	save_flags(flags);
+	cli();
+	failed = --(sem->count) < 0;
+	restore_flags(flags);
+	if(failed)
+		failed = __down_interruptible(sem);
+	return(failed);
+}
+
+extern inline int down_trylock(struct semaphore * sem)
+{
+	unsigned long flags;
+	int failed;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	save_flags(flags);
+	cli();
+	failed = --(sem->count) < 0;
+	restore_flags(flags);
+	if(failed)
+		failed = __down_trylock(sem);
+	return(failed);
+}
+
+/*
+ * 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)
+{  
+	unsigned long flags;
+	int wakeup;
+
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
+
+	/* atomically increment the semaphores count, and if it was negative, we wake people */
+	save_flags(flags);
+	cli();
+	wakeup = ++(sem->count) <= 0;
+	restore_flags(flags);
+	if(wakeup) {
+		__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).
+ *
+ * In terms of fairness, this should result in the lock
+ * flopping back and forth between readers and writers
+ * under heavy use.
+ *
+ *              -ben
+ */
+
+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)
+{
+#if WAITQUEUE_DEBUG
+        CHECK_MAGIC(sem->__magic);
+        if (sem->granted & 2)
+                BUG();
+        if (atomic_read(&sem->writers))
+                BUG();
+        atomic_dec(&sem->readers);
+#endif
+
+        mb();
+        if (atomic_inc_return(&sem->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