1 files changed, 164 insertions, 0 deletions
diff --git a/arch/mips/kernel/semaphore.c b/arch/mips/kernel/semaphore.c
new file mode 100644
index 000000000000..9c40fe5a8e8d
--- /dev/null
+++ b/arch/mips/kernel/semaphore.c
@@ -0,0 +1,164 @@
+/*
+ * MIPS-specific semaphore code.
+ *
+ * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
+ * Copyright (C) 2004 Ralf Baechle <ralf@linux-mips.org>
+ *
+ * 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/module.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <asm/atomic.h>
+#include <asm/cpu-features.h>
+#include <asm/errno.h>
+#include <asm/semaphore.h>
+#include <asm/war.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;
+ *
+ * On machines without lld/scd we need a spinlock to make the manipulation of
+ * sem->count and sem->waking atomic.  Scalability isn't an issue because
+ * this lock is used on UP only so it's just an empty variable.
+ */
+static inline int __sem_update_count(struct semaphore *sem, int incr)
+{
+	int old_count, tmp;
+
+	if (cpu_has_llsc && R10000_LLSC_WAR) {
+		__asm__ __volatile__(
+		"1:	ll	%0, %2					\n"
+		"	sra	%1, %0, 31				\n"
+		"	not	%1					\n"
+		"	and	%1, %0, %1				\n"
+		"	add	%1, %1, %3				\n"
+		"	sc	%1, %2					\n"
+		"	beqzl	%1, 1b					\n"
+		: "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
+		: "r" (incr), "m" (sem->count));
+	} else if (cpu_has_llsc) {
+		__asm__ __volatile__(
+		"1:	ll	%0, %2					\n"
+		"	sra	%1, %0, 31				\n"
+		"	not	%1					\n"
+		"	and	%1, %0, %1				\n"
+		"	add	%1, %1, %3				\n"
+		"	sc	%1, %2					\n"
+		"	beqz	%1, 1b					\n"
+		: "=&r" (old_count), "=&r" (tmp), "=m" (sem->count)
+		: "r" (incr), "m" (sem->count));
+	} else {
+		static DEFINE_SPINLOCK(semaphore_lock);
+		unsigned long flags;
+
+		spin_lock_irqsave(&semaphore_lock, flags);
+		old_count = atomic_read(&sem->count);
+		tmp = max_t(int, old_count, 0) + incr;
+		atomic_set(&sem->count, tmp);
+		spin_unlock_irqrestore(&semaphore_lock, flags);
+	}
+
+	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);