From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@ppc970.osdl.org>
Date: Sat, 16 Apr 2005 15:20:36 -0700
Subject: Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
---
 arch/parisc/kernel/semaphore.c | 102 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 102 insertions(+)
 create mode 100644 arch/parisc/kernel/semaphore.c

(limited to 'arch/parisc/kernel/semaphore.c')

diff --git a/arch/parisc/kernel/semaphore.c b/arch/parisc/kernel/semaphore.c
new file mode 100644
index 00000000000..ee806bcc372
--- /dev/null
+++ b/arch/parisc/kernel/semaphore.c
@@ -0,0 +1,102 @@
+/*
+ * Semaphore implementation Copyright (c) 2001 Matthew Wilcox, Hewlett-Packard
+ */
+
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+
+/*
+ * Semaphores are complex as we wish to avoid using two variables.
+ * `count' has multiple roles, depending on its value.  If it is positive
+ * or zero, there are no waiters.  The functions here will never be
+ * called; see <asm/semaphore.h>
+ *
+ * When count is -1 it indicates there is at least one task waiting
+ * for the semaphore.
+ *
+ * When count is less than that, there are '- count - 1' wakeups
+ * pending.  ie if it has value -3, there are 2 wakeups pending.
+ *
+ * Note that these functions are only called when there is contention
+ * on the lock, and as such all this is the "non-critical" part of the
+ * whole semaphore business. The critical part is the inline stuff in
+ * <asm/semaphore.h> where we want to avoid any extra jumps and calls.
+ */
+void __up(struct semaphore *sem)
+{
+	sem->count--;
+	wake_up(&sem->wait);
+}
+
+#define wakers(count) (-1 - count)
+
+#define DOWN_HEAD							\
+	int ret = 0;							\
+	DECLARE_WAITQUEUE(wait, current);				\
+									\
+	/* Note that someone is waiting */				\
+	if (sem->count == 0)						\
+		sem->count = -1;					\
+									\
+	/* protected by the sentry still -- use unlocked version */	\
+	wait.flags = WQ_FLAG_EXCLUSIVE;					\
+	__add_wait_queue_tail(&sem->wait, &wait);			\
+ lost_race:								\
+	spin_unlock_irq(&sem->sentry);					\
+
+#define DOWN_TAIL							\
+	spin_lock_irq(&sem->sentry);					\
+	if (wakers(sem->count) == 0 && ret == 0)			\
+		goto lost_race;	/* Someone stole our wakeup */		\
+	__remove_wait_queue(&sem->wait, &wait);				\
+	current->state = TASK_RUNNING;					\
+	if (!waitqueue_active(&sem->wait) && (sem->count < 0))		\
+		sem->count = wakers(sem->count);
+
+#define UPDATE_COUNT							\
+	sem->count += (sem->count < 0) ? 1 : - 1;
+	
+
+void __sched __down(struct semaphore * sem)
+{
+	DOWN_HEAD
+
+	for(;;) {
+		set_task_state(current, TASK_UNINTERRUPTIBLE);
+		/* we can _read_ this without the sentry */
+		if (sem->count != -1)
+			break;
+ 		schedule();
+ 	}
+
+	DOWN_TAIL
+	UPDATE_COUNT
+}
+
+int __sched __down_interruptible(struct semaphore * sem)
+{
+	DOWN_HEAD
+
+	for(;;) {
+		set_task_state(current, TASK_INTERRUPTIBLE);
+		/* we can _read_ this without the sentry */
+		if (sem->count != -1)
+			break;
+
+		if (signal_pending(current)) {
+			ret = -EINTR;
+			break;
+		}
+		schedule();
+	}
+
+	DOWN_TAIL
+
+	if (!ret) {
+		UPDATE_COUNT
+	}
+
+	return ret;
+}
-- 
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