1 files changed, 136 insertions, 0 deletions

diff --git a/arch/ppc64/kernel/semaphore.c b/arch/ppc64/kernel/semaphore.c
new file mode 100644
index 000000000000..a1c1db573e9c
--- /dev/null
+++ b/arch/ppc64/kernel/semaphore.c
@@ -0,0 +1,136 @@
+/*
+ * 
+ *
+ * PowerPC-specific semaphore code.
+ *
+ * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ *
+ * April 2001 - Reworked by Paul Mackerras <paulus@samba.org>
+ * to eliminate the SMP races in the old version between the updates
+ * of `count' and `waking'.  Now we use negative `count' values to
+ * indicate that some process(es) are waiting for the semaphore.
+ */
+
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/module.h>
+
+#include <asm/atomic.h>
+#include <asm/semaphore.h>
+#include <asm/errno.h>
+
+/*
+ * Atomically update sem->count.
+ * This does the equivalent of the following:
+ *
+ *      old_count = sem->count;
+ *      tmp = MAX(old_count, 0) + incr;
+ *      sem->count = tmp;
+ *      return old_count;
+ */
+static inline int __sem_update_count(struct semaphore *sem, int incr)
+{
+        int old_count, tmp;
+
+        __asm__ __volatile__("\n"
+"1:     lwarx   %0,0,%3\n"
+"       srawi   %1,%0,31\n"
+"       andc    %1,%0,%1\n"
+"       add     %1,%1,%4\n"
+"       stwcx.  %1,0,%3\n"
+"       bne     1b"
+        : "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
+        : "r" (&sem->count), "r" (incr), "m" (sem->count)
+        : "cc");
+
+        return old_count;
+}
+
+void __up(struct semaphore *sem)
+{
+        /*
+         * Note that we incremented count in up() before we came here,
+         * but that was ineffective since the result was <= 0, and
+         * any negative value of count is equivalent to 0.
+         * This ends up setting count to 1, unless count is now > 0
+         * (i.e. because some other cpu has called up() in the meantime),
+         * in which case we just increment count.
+         */
+        __sem_update_count(sem, 1);
+        wake_up(&sem->wait);
+}
+EXPORT_SYMBOL(__up);
+
+/*
+ * Note that when we come in to __down or __down_interruptible,
+ * we have already decremented count, but that decrement was
+ * ineffective since the result was < 0, and any negative value
+ * of count is equivalent to 0.
+ * Thus it is only when we decrement count from some value > 0
+ * that we have actually got the semaphore.
+ */
+void __sched __down(struct semaphore *sem)
+{
+        struct task_struct *tsk = current;
+        DECLARE_WAITQUEUE(wait, tsk);
+
+        __set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+        add_wait_queue_exclusive(&sem->wait, &wait);
+
+        /*
+         * Try to get the semaphore.  If the count is > 0, then we've
+         * got the semaphore; we decrement count and exit the loop.
+         * If the count is 0 or negative, we set it to -1, indicating
+         * that we are asleep, and then sleep.
+         */
+        while (__sem_update_count(sem, -1) <= 0) {
+                schedule();
+                set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+        }
+        remove_wait_queue(&sem->wait, &wait);
+        __set_task_state(tsk, TASK_RUNNING);
+
+        /*
+         * If there are any more sleepers, wake one of them up so
+         * that it can either get the semaphore, or set count to -1
+         * indicating that there are still processes sleeping.
+         */
+        wake_up(&sem->wait);
+}
+EXPORT_SYMBOL(__down);
+
+int __sched __down_interruptible(struct semaphore * sem)
+{
+        int retval = 0;
+        struct task_struct *tsk = current;
+        DECLARE_WAITQUEUE(wait, tsk);
+
+        __set_task_state(tsk, TASK_INTERRUPTIBLE);
+        add_wait_queue_exclusive(&sem->wait, &wait);
+
+        while (__sem_update_count(sem, -1) <= 0) {
+                if (signal_pending(current)) {
+                        /*
+                         * A signal is pending - give up trying.
+                         * Set sem->count to 0 if it is negative,
+                         * since we are no longer sleeping.
+                         */
+                        __sem_update_count(sem, 0);
+                        retval = -EINTR;
+                        break;
+                }
+                schedule();
+                set_task_state(tsk, TASK_INTERRUPTIBLE);
+        }
+        remove_wait_queue(&sem->wait, &wait);
+        __set_task_state(tsk, TASK_RUNNING);
+
+        wake_up(&sem->wait);
+        return retval;
+}
+EXPORT_SYMBOL(__down_interruptible);