1 files changed, 188 insertions, 0 deletions

diff --git a/include/asm-ia64/rwsem.h b/include/asm-ia64/rwsem.h
new file mode 100644
index 000000000000..6ece5061dc19
--- /dev/null
+++ b/include/asm-ia64/rwsem.h
@@ -0,0 +1,188 @@
+/*
+ * asm-ia64/rwsem.h: R/W semaphores for ia64
+ *
+ * Copyright (C) 2003 Ken Chen <kenneth.w.chen@intel.com>
+ * Copyright (C) 2003 Asit Mallick <asit.k.mallick@intel.com>
+ *
+ * Based on asm-i386/rwsem.h and other architecture implementation.
+ *
+ * The MSW of the count is the negated number of active writers and
+ * waiting lockers, and the LSW is the total number of active locks.
+ *
+ * The lock count is initialized to 0 (no active and no waiting lockers).
+ *
+ * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case
+ * of an uncontended lock. Readers increment by 1 and see a positive value
+ * when uncontended, negative if there are writers (and maybe) readers
+ * waiting (in which case it goes to sleep).
+ */
+
+#ifndef _ASM_IA64_RWSEM_H
+#define _ASM_IA64_RWSEM_H
+
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
+#include <asm/intrinsics.h>
+
+/*
+ * the semaphore definition
+ */
+struct rw_semaphore {
+        signed int              count;
+        spinlock_t              wait_lock;
+        struct list_head        wait_list;
+#if RWSEM_DEBUG
+        int                     debug;
+#endif
+};
+
+#define RWSEM_UNLOCKED_VALUE            0x00000000
+#define RWSEM_ACTIVE_BIAS               0x00000001
+#define RWSEM_ACTIVE_MASK               0x0000ffff
+#define RWSEM_WAITING_BIAS              (-0x00010000)
+#define RWSEM_ACTIVE_READ_BIAS          RWSEM_ACTIVE_BIAS
+#define RWSEM_ACTIVE_WRITE_BIAS         (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
+
+/*
+ * initialization
+ */
+#if RWSEM_DEBUG
+#define __RWSEM_DEBUG_INIT      , 0
+#else
+#define __RWSEM_DEBUG_INIT      /* */
+#endif
+
+#define __RWSEM_INITIALIZER(name) \
+        { RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, \
+          LIST_HEAD_INIT((name).wait_list) \
+          __RWSEM_DEBUG_INIT }
+
+#define DECLARE_RWSEM(name) \
+        struct rw_semaphore name = __RWSEM_INITIALIZER(name)
+
+extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
+extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
+
+static inline void
+init_rwsem (struct rw_semaphore *sem)
+{
+        sem->count = RWSEM_UNLOCKED_VALUE;
+        spin_lock_init(&sem->wait_lock);
+        INIT_LIST_HEAD(&sem->wait_list);
+#if RWSEM_DEBUG
+        sem->debug = 0;
+#endif
+}
+
+/*
+ * lock for reading
+ */
+static inline void
+__down_read (struct rw_semaphore *sem)
+{
+        int result = ia64_fetchadd4_acq((unsigned int *)&sem->count, 1);
+
+        if (result < 0)
+                rwsem_down_read_failed(sem);
+}
+
+/*
+ * lock for writing
+ */
+static inline void
+__down_write (struct rw_semaphore *sem)
+{
+        int old, new;
+
+        do {
+                old = sem->count;
+                new = old + RWSEM_ACTIVE_WRITE_BIAS;
+        } while (cmpxchg_acq(&sem->count, old, new) != old);
+
+        if (old != 0)
+                rwsem_down_write_failed(sem);
+}
+
+/*
+ * unlock after reading
+ */
+static inline void
+__up_read (struct rw_semaphore *sem)
+{
+        int result = ia64_fetchadd4_rel((unsigned int *)&sem->count, -1);
+
+        if (result < 0 && (--result & RWSEM_ACTIVE_MASK) == 0)
+                rwsem_wake(sem);
+}
+
+/*
+ * unlock after writing
+ */
+static inline void
+__up_write (struct rw_semaphore *sem)
+{
+        int old, new;
+
+        do {
+                old = sem->count;
+                new = old - RWSEM_ACTIVE_WRITE_BIAS;
+        } while (cmpxchg_rel(&sem->count, old, new) != old);
+
+        if (new < 0 && (new & RWSEM_ACTIVE_MASK) == 0)
+                rwsem_wake(sem);
+}
+
+/*
+ * trylock for reading -- returns 1 if successful, 0 if contention
+ */
+static inline int
+__down_read_trylock (struct rw_semaphore *sem)
+{
+        int tmp;
+        while ((tmp = sem->count) >= 0) {
+                if (tmp == cmpxchg_acq(&sem->count, tmp, tmp+1)) {
+                        return 1;
+                }
+        }
+        return 0;
+}
+
+/*
+ * trylock for writing -- returns 1 if successful, 0 if contention
+ */
+static inline int
+__down_write_trylock (struct rw_semaphore *sem)
+{
+        int tmp = cmpxchg_acq(&sem->count, RWSEM_UNLOCKED_VALUE,
+                              RWSEM_ACTIVE_WRITE_BIAS);
+        return tmp == RWSEM_UNLOCKED_VALUE;
+}
+
+/*
+ * downgrade write lock to read lock
+ */
+static inline void
+__downgrade_write (struct rw_semaphore *sem)
+{
+        int old, new;
+
+        do {
+                old = sem->count;
+                new = old - RWSEM_WAITING_BIAS;
+        } while (cmpxchg_rel(&sem->count, old, new) != old);
+
+        if (old < 0)
+                rwsem_downgrade_wake(sem);
+}
+
+/*
+ * Implement atomic add functionality.  These used to be "inline" functions, but GCC v3.1
+ * doesn't quite optimize this stuff right and ends up with bad calls to fetchandadd.
+ */
+#define rwsem_atomic_add(delta, sem)    atomic_add(delta, (atomic_t *)(&(sem)->count))
+#define rwsem_atomic_update(delta, sem) atomic_add_return(delta, (atomic_t *)(&(sem)->count))
+
+#endif /* _ASM_IA64_RWSEM_H */