From 9f2daa69db3e192c8a3e4da35fb59a4c84918d5b Mon Sep 17 00:00:00 2001
From: Ralf Baechle <ralf@linux-mips.org>
Date: Sun, 23 Jan 2000 21:15:52 +0000
Subject: Let's start the run on SMP.  Here are the spinlocks.

---
 include/asm-mips/spinlock.h | 141 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 139 insertions(+), 2 deletions(-)

(limited to 'include/asm-mips')

diff --git a/include/asm-mips/spinlock.h b/include/asm-mips/spinlock.h
index ece1f7ddd..36e7c974d 100644
--- a/include/asm-mips/spinlock.h
+++ b/include/asm-mips/spinlock.h
@@ -1,8 +1,145 @@
-/* $Id: spinlock.h,v 1.6 1999/06/22 23:49:12 ralf Exp $
+/* $Id$
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 1999, 2000 by Ralf Baechle
+ * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
  */
 #ifndef _ASM_SPINLOCK_H
 #define _ASM_SPINLOCK_H
 
-#error "Nix SMP on MIPS"
+/*
+ * Your basic SMP spinlocks, allowing only a single CPU anywhere
+ */
+
+typedef struct {
+	volatile unsigned int lock;
+} spinlock_t;
+
+#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
+
+#define spin_lock_init(x)	do { (x)->lock = 0; } while(0);
+
+/*
+ * Simple spin lock operations.  There are two variants, one clears IRQ's
+ * on the local processor, one does not.
+ *
+ * We make no fairness assumptions.  They have a cost.
+ */
+
+typedef struct { unsigned long a[100]; } __dummy_lock_t;
+#define __dummy_lock(lock) (*(__dummy_lock_t *)(lock))
+
+static inline void spin_lock(spinlock_t *lock)
+{
+	unsigned int tmp;
+
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# spin_lock\n"
+	"1:\tll\t%1, %2\n\t"
+	"bnez\t%1, 1b\n\t"
+	" li\t%1, 1\n\t"
+	"sc\t%1, %0\n\t"
+	"beqz\t%1, 1b\n\t"
+	" sync\n\t"
+	".set\treorder"
+	: "=o" (__dummy_lock(lock)), "=&r" (tmp)
+	: "o" (__dummy_lock(lock)));
+}
+
+static inline void spin_unlock(spinlock_t *lock)
+{
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# spin_unlock\n\t"
+	"sync\n\t"
+	"sw\t$0, %0\n\t"
+	".set\treorder"	
+	: "=o" (__dummy_lock(lock))
+	: "o" (__dummy_lock(lock))
+	: "memory");
+}
+
+#define spin_trylock(lock) (!test_and_set_bit(0,(lock)))
+
+/*
+ * Read-write spinlocks, allowing multiple readers but only one writer.
+ *
+ * NOTE! it is quite common to have readers in interrupts but no interrupt
+ * writers. For those circumstances we can "mix" irq-safe locks - any writer
+ * needs to get a irq-safe write-lock, but readers can get non-irqsafe
+ * read-locks.
+ */
+
+typedef struct {
+	volatile unsigned int lock;
+} rwlock_t;
+
+#define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
+
+static inline void read_lock(rwlock_t *rw)
+{
+	unsigned int tmp;
+
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# read_lock\n"
+	"1:\tll\t%1, %2\n\t"
+	"bltz\t%1, 1b\n\t"
+	" addu\t%1, 1\n\t"
+	"sc\t%1, %0\n\t"
+	"beqz\t%1, 1b\n\t"
+	" sync\n\t"
+	".set\treorder"	
+	: "=o" (__dummy_lock(rw)), "=&r" (tmp)
+	: "o" (__dummy_lock(rw)));
+}
+
+/* Note the use of sub, not subu which will make the kernel die with an
+   overflow exception if we ever try to unlock an rwlock that is already
+   unlocked or is being held by a writer.  */
+static inline void read_unlock(rwlock_t *rw)
+{
+	unsigned int tmp;
+
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# read_unlock\n"
+	"1:\tll\t%1, %2\n\t"
+	"sub\t%1, 1\n\t"
+	"sc\t%1, %0\n\t"
+	"beqz\t%1, 1b\n\t"
+	".set\treorder"	
+	: "=o" (__dummy_lock(rw)), "=&r" (tmp)
+	: "o" (__dummy_lock(rw)));
+}
+
+static inline void write_lock(rwlock_t *rw)
+{
+	unsigned int tmp;
+
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# write_lock\n"
+	"1:\tll\t%1, %2\n\t"
+	"bnez\t%1, 1b\n\t"
+	" lui\t%1, 0x8000\n\t"
+	"sc\t%1, %0\n\t"
+	"beqz\t%1, 1b\n\t"
+	" sync\n\t"
+	".set\treorder"	
+	: "=o" (__dummy_lock(rw)), "=&r" (tmp)
+	: "o" (__dummy_lock(rw)));
+}
+
+static inline void write_unlock(rwlock_t *rw)
+{
+	__asm__ __volatile__(
+	".set\tnoreorder\t\t\t# write_unlock\n\t"
+	"sync\n\t"
+	"sw\t$0, %0\n\t"
+	".set\treorder"	
+	: "=o" (__dummy_lock(rw))
+	: "o" (__dummy_lock(rw))
+	: "memory");
+}
 
 #endif /* _ASM_SPINLOCK_H */
-- 
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