From ff28d8ce709b1137516ff67a7c398ccf3c93ab5e Mon Sep 17 00:00:00 2001
From: Ralf Baechle <ralf@linux-mips.org>
Date: Wed, 20 Oct 1999 21:09:19 +0000
Subject: Rewrite of semaphores for MIPS64.

---
 include/asm-mips64/semaphore-helper.h | 116 ++++++++++++++++++++--------------
 1 file changed, 70 insertions(+), 46 deletions(-)

(limited to 'include/asm-mips64/semaphore-helper.h')

diff --git a/include/asm-mips64/semaphore-helper.h b/include/asm-mips64/semaphore-helper.h
index d685b89e6..908d16c4b 100644
--- a/include/asm-mips64/semaphore-helper.h
+++ b/include/asm-mips64/semaphore-helper.h
@@ -5,6 +5,7 @@
  * (C) Copyright 1996 Linus Torvalds
  * (C) Copyright 1999 Andrea Arcangeli
  * (C) Copyright 1999 Ralf Baechle
+ * (C) Copyright 1999 Silicon Graphics, Inc.
  */
 #ifndef _ASM_SEMAPHORE_HELPER_H
 #define _ASM_SEMAPHORE_HELPER_H
@@ -23,11 +24,11 @@ waking_non_zero(struct semaphore *sem)
 	int ret, tmp;
 
 	__asm__ __volatile__(
-	"1:\tll\t%1,%2\n\t"
-	"blez\t%1,2f\n\t"
-	"subu\t%0,%1,1\n\t"
-	"sc\t%0,%2\n\t"
-	"beqz\t%0,1b\n\t"
+	"1:\tll\t%1, %2\n\t"
+	"blez\t%1, 2f\n\t"
+	"subu\t%0, %1, 1\n\t"
+	"sc\t%0, %2\n\t"
+	"beqz\t%0, 1b\n\t"
 	"2:"
 	".text"
 	: "=r"(ret), "=r"(tmp), "=m"(__atomic_fool_gcc(&sem->waking))
@@ -48,78 +49,101 @@ waking_non_zero(struct semaphore *sem)
  *
  * This is accomplished by doing a 64-bit ll/sc on the 2 32-bit words.
  *
- * This is crazy.  Normally it stricly forbidden to use 64-bit operation
- * in the 32-bit MIPS kernel.  In this case it's however ok because if an
- * interrupt has destroyed the upper half of registers sc will fail.
+ * Pseudocode:
+ *
+ * If(sem->waking > 0) {
+ *	Decrement(sem->waking)
+ *	Return(SUCCESS)
+ * } else If(segnal_pending(tsk)) {
+ *	Increment(sem->count)
+ *	Return(-EINTR)
+ * } else {
+ *	Return(SLEEP)
+ * }
  */
+
 static inline int
 waking_non_zero_interruptible(struct semaphore *sem, struct task_struct *tsk)
 {
 	long ret, tmp;
 
 #ifdef __MIPSEB__
+
         __asm__ __volatile__("
-	.set	mips3
 	.set	push
 	.set	noat
-0:	lld	%1,%2
-	li	%0,0
+0:	lld	%1, %2
+	li	%0, 0
+	sll	$1, %1, 0
+	blez	$1, 1f
+	daddiu	%1, %1, -1
+	li	%0, 1
+	b 	2f
+1:
+	beqz	%3, 2f
+	li	%0, %4
+	dli	$1, 0x0000000100000000
+	daddu	%1, %1, $1
+2:
+	scd	%1, %2
+	beqz	%1, 0b
+	.set	pop"
+	: "=&r"(ret), "=&r"(tmp), "=m"(*sem)
+	: "r"(signal_pending(tsk)), "i"(-EINTR));
+
+#elif defined(__MIPSEL__)
 
-	bltz	%1, 1f
-	dli	$1, 0xffffffff00000000
-	daddu	%1, $1
+	__asm__ __volatile__("
+	.set	push
+	.set	noat
+0:
+	lld	%1, %2
+	li	%0, 0
+	blez	%1, 1f
+	dli	$1, 0x0000000100000000
+	dsubu	%1, %1, $1
 	li	%0, 1
 	b	2f
 1:
-
-	beqz	%3, 1f
-	addiu	$1, %1, 1
+	beqz	%3, 2f
+	li	%0, %4
+	/* 
+	 * It would be nice to assume that sem->count
+	 * is != -1, but we will guard against that case
+	 */
+	daddiu	$1, %1, 1
 	dsll32	$1, $1, 0
 	dsrl32	$1, $1, 0
 	dsrl32	%1, %1, 0
 	dsll32	%1, %1, 0
-	or	%1, $1
-	li	%0, %4
-	b	2f
-1:
-	scd	%1, %2
+	or	%1, %1, $1
 2:
-	beqz	%1,0b
-	.set	pop
-	.set	mips0"
+	scd	%1, %2
+	beqz	%1, 0b
+	.set	pop"
 	: "=&r"(ret), "=&r"(tmp), "=m"(*sem)
 	: "r"(signal_pending(tsk)), "i"(-EINTR));
-#endif
 
-#ifdef __MIPSEL__
-#error "FIXME: waking_non_zero_interruptible doesn't support little endian machines yet."
+#else
+#error "MIPS but neither __MIPSEL__ nor __MIPSEB__?"
 #endif
 
 	return ret;
 }
 
 /*
- * waking_non_zero_trylock:
- *	1	failed to lock
- *	0	got the lock
- *
- * XXX SMP ALERT
+ * waking_non_zero_trylock is unused.  we do everything in 
+ * down_trylock and let non-ll/sc hosts bounce around.
  */
-#ifdef __SMP__
-#error FIXME, waking_non_zero_trylock is broken for SMP.
-#endif
-static inline int waking_non_zero_trylock(struct semaphore *sem)
-{
-        int ret = 1;
 
-	if (atomic_read(&sem->waking) <= 0)
-		atomic_inc(&sem->count);
-	else {
-		atomic_dec(&sem->waking);
-		ret = 0;
-	}
+static inline int
+waking_non_zero_trylock(struct semaphore *sem)
+{
+#if WAITQUEUE_DEBUG
+	CHECK_MAGIC(sem->__magic);
+#endif
 
-	return ret;
+	return 0;
 }
 
 #endif /* _ASM_SEMAPHORE_HELPER_H */
-- 
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