[LV-kern-commit] CVS: kernel-2.4/include/asm-vax semaphore-helper.h,1.1,1.2 semaphore.h,1.3,1.4

[Kenn H. <ke...@us...>]

Update of /cvsroot/linux-vax/kernel-2.4/include/asm-vax
In directory usw-pr-cvs1:/tmp/cvs-serv26415

Modified Files:
	semaphore-helper.h semaphore.h 
Log Message:
Rather than fight with the current VAX versions of semaphore.h and
semaphore-helper.h (which seemed to have rotted quite a bit), I just
took a look at the S390 implementations.  The S390 files didn't have
any platform-specific bits, so I've just stolen them en masse.  As
long as we get the atomic_xxx operations sorted, it should work OK.


Index: semaphore-helper.h
===================================================================
RCS file: /cvsroot/linux-vax/kernel-2.4/include/asm-vax/semaphore-helper.h,v
retrieving revision 1.1
retrieving revision 1.2
diff -u -r1.1 -r1.2
--- semaphore-helper.h	2001/01/17 16:18:52	1.1
+++ semaphore-helper.h	2001/01/29 00:47:41	1.2
@@ -1,13 +1,19 @@
-#ifndef _VAX_SEMAPHORE_HELPER_H
-#define _VAX_SEMAPHORE_HELPER_H
-
 /*
- * SMP- and interrupt-safe semaphores helper functions.
+ *  $Id$
+ * 
+ *  VAX version based on S390 version
  *
- * (C) Copyright 1996 Linus Torvalds
- * (C) Copyright 1999 Andrea Arcangeli
+ *  S390 version
+ *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
+ *
+ *  Derived from "include/asm-i386/semaphore-helper.h"
+ *    (C) Copyright 1996 Linus Torvalds
+ *    (C) Copyright 1999 Andrea Arcangeli
  */
 
+#ifndef _VAX_SEMAPHORE_HELPER_H
+#define _VAX_SEMAPHORE_HELPER_H
+
 /*
  * These two _must_ execute atomically wrt each other.
  *
@@ -19,34 +25,12 @@
 	unsigned long flags;
 
 	spin_lock_irqsave(&semaphore_wake_lock, flags);
-	if (atomic_read(&sem->count) <= 0)
-		sem->waking++;
+	sem->waking++;
 	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
 }
 
 static inline int waking_non_zero(struct semaphore *sem)
 {
-	int ret;
-        /* FIXME: use interlocked instructions (ADAWI, atp 1998) */
-	__asm__ __volatile__( 
-		"S1:	movl %1,%0\n"
-		"	tstl %0\n"
-		"       beql S2\n"	     
-		"	decl %1\n"
-		"S2:"
-		: "=r" (ret)
-		: "r" (&sem->waking)
-		: "r0", "memory");
-
-	return ret;
-}
-
-/* FIXME: this is the original, is the above equivalent? It was in Nov 98,
- * but this has changed recently 
- */
-/*
-static inline int waking_non_zero(struct semaphore *sem)
-{
 	unsigned long flags;
 	int ret = 0;
 
@@ -58,16 +42,18 @@
 	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
 	return ret;
 }
-*/
+
 /*
  * waking_non_zero_interruptible:
  *	1	got the lock
  *	0	go to sleep
  *	-EINTR	interrupted
  *
- * We must undo the sem->count down_interruptible() increment while we are
- * protected by the spinlock in order to make atomic this atomic_inc() with the
- * atomic_read() in wake_one_more(), otherwise we can race. -arca
+ * If we give up we must undo our count-decrease we previously did in down().
+ * Subtle: up() can continue to happens and increase the semaphore count
+ * even during our critical section protected by the spinlock. So
+ * we must remeber to undo the sem->waking that will be run from
+ * wake_one_more() some time soon, if the semaphore count become > 0.
  */
 static inline int waking_non_zero_interruptible(struct semaphore *sem,
 						struct task_struct *tsk)
@@ -80,7 +66,8 @@
 		sem->waking--;
 		ret = 1;
 	} else if (signal_pending(tsk)) {
-		atomic_inc(&sem->count);
+               if (atomic_inc_and_test_greater_zero(&sem->count))
+                       sem->waking--;
 		ret = -EINTR;
 	}
 	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
@@ -92,9 +79,7 @@
  *	1	failed to lock
  *	0	got the lock
  *
- * We must undo the sem->count down_trylock() increment while we are
- * protected by the spinlock in order to make atomic this atomic_inc() with the
- * atomic_read() in wake_one_more(), otherwise we can race. -arca
+ * Implementation details are the same of the interruptible case.
  */
 static inline int waking_non_zero_trylock(struct semaphore *sem)
 {
@@ -103,13 +88,16 @@
 
 	spin_lock_irqsave(&semaphore_wake_lock, flags);
 	if (sem->waking <= 0)
-		atomic_inc(&sem->count);
-	else {
+        {
+                if (atomic_inc_and_test_greater_zero(&sem->count))
+                        sem->waking--;
+        } else {
 		sem->waking--;
 		ret = 0;
 	}
 	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
 	return ret;
 }
+
+#endif /* _VAX_SEMAPHORE_HELPER_H */
 
-#endif 

Index: semaphore.h
===================================================================
RCS file: /cvsroot/linux-vax/kernel-2.4/include/asm-vax/semaphore.h,v
retrieving revision 1.3
retrieving revision 1.4
diff -u -r1.3 -r1.4
--- semaphore.h	2001/01/29 00:44:39	1.3
+++ semaphore.h	2001/01/29 00:47:41	1.4
@@ -191,4 +191,3 @@
 }
 
 #endif /* _VAX_SEMAPHORE_H */
-