Generic semaphore implementation

Semaphores are no longer performance-critical, so a generic C
implementation is better for maintainability, debuggability and
extensibility.  Thanks to Peter Zijlstra for fixing the lockdep
warning.  Thanks to Harvey Harrison for pointing out that the
unlikely() was unnecessary.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Acked-by: Ingo Molnar <mingo@elte.hu>

3 files changed, 1 insertions, 360 deletions

diff --git a/include/asm-x86/semaphore.h b/include/asm-x86/semaphore.h
index 572c0b67a6b..d9b2034ed1d 100644
--- a/include/asm-x86/semaphore.h
+++ b/include/asm-x86/semaphore.h
@@ -1,5 +1 @@
-#ifdef CONFIG_X86_32
-# include "semaphore_32.h"
-#else
-# include "semaphore_64.h"
-#endif
+#include <linux/semaphore.h>
diff --git a/include/asm-x86/semaphore_32.h b/include/asm-x86/semaphore_32.h
deleted file mode 100644
index ac96d3804d0..00000000000
--- a/include/asm-x86/semaphore_32.h
+++ /dev/null
@@ -1,175 +0,0 @@
-#ifndef _I386_SEMAPHORE_H
-#define _I386_SEMAPHORE_H
-
-#include <linux/linkage.h>
-
-#ifdef __KERNEL__
-
-/*
- * SMP- and interrupt-safe semaphores..
- *
- * (C) Copyright 1996 Linus Torvalds
- *
- * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
- *                     the original code and to make semaphore waits
- *                     interruptible so that processes waiting on
- *                     semaphores can be killed.
- * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
- *		       functions in asm/sempahore-helper.h while fixing a
- *		       potential and subtle race discovered by Ulrich Schmid
- *		       in down_interruptible(). Since I started to play here I
- *		       also implemented the `trylock' semaphore operation.
- *          1999-07-02 Artur Skawina <skawina@geocities.com>
- *                     Optimized "0(ecx)" -> "(ecx)" (the assembler does not
- *                     do this). Changed calling sequences from push/jmp to
- *                     traditional call/ret.
- * Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
- *		       Some hacks to ensure compatibility with recent
- *		       GCC snapshots, to avoid stack corruption when compiling
- *		       with -fomit-frame-pointer. It's not sure if this will
- *		       be fixed in GCC, as our previous implementation was a
- *		       bit dubious.
- *
- * If you would like to see an analysis of this implementation, please
- * ftp to gcom.com and download the file
- * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
- *
- */
-
-#include <asm/system.h>
-#include <asm/atomic.h>
-#include <linux/wait.h>
-#include <linux/rwsem.h>
-
-struct semaphore {
-	atomic_t count;
-	int sleepers;
-	wait_queue_head_t wait;
-};
-
-
-#define __SEMAPHORE_INITIALIZER(name, n)				\
-{									\
-	.count		= ATOMIC_INIT(n),				\
-	.sleepers	= 0,						\
-	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
-}
-
-#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
-	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
-
-#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
-
-static inline void sema_init (struct semaphore *sem, int val)
-{
-/*
- *	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
- *
- * i'd rather use the more flexible initialization above, but sadly
- * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
- */
-	atomic_set(&sem->count, val);
-	sem->sleepers = 0;
-	init_waitqueue_head(&sem->wait);
-}
-
-static inline void init_MUTEX (struct semaphore *sem)
-{
-	sema_init(sem, 1);
-}
-
-static inline void init_MUTEX_LOCKED (struct semaphore *sem)
-{
-	sema_init(sem, 0);
-}
-
-extern asmregparm void __down_failed(atomic_t *count_ptr);
-extern asmregparm int  __down_failed_interruptible(atomic_t *count_ptr);
-extern asmregparm int  __down_failed_trylock(atomic_t *count_ptr);
-extern asmregparm void __up_wakeup(atomic_t *count_ptr);
-
-/*
- * This is ugly, but we want the default case to fall through.
- * "__down_failed" is a special asm handler that calls the C
- * routine that actually waits. See arch/i386/kernel/semaphore.c
- */
-static inline void down(struct semaphore * sem)
-{
-	might_sleep();
-	__asm__ __volatile__(
-		"# atomic down operation\n\t"
-		LOCK_PREFIX "decl %0\n\t"     /* --sem->count */
-		"jns 2f\n"
-		"\tlea %0,%%eax\n\t"
-		"call __down_failed\n"
-		"2:"
-		:"+m" (sem->count)
-		:
-		:"memory","ax");
-}
-
-/*
- * Interruptible try to acquire a semaphore.  If we obtained
- * it, return zero.  If we were interrupted, returns -EINTR
- */
-static inline int down_interruptible(struct semaphore * sem)
-{
-	int result;
-
-	might_sleep();
-	__asm__ __volatile__(
-		"# atomic interruptible down operation\n\t"
-		"xorl %0,%0\n\t"
-		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
-		"jns 2f\n\t"
-		"lea %1,%%eax\n\t"
-		"call __down_failed_interruptible\n"
-		"2:"
-		:"=&a" (result), "+m" (sem->count)
-		:
-		:"memory");
-	return result;
-}
-
-/*
- * Non-blockingly attempt to down() a semaphore.
- * Returns zero if we acquired it
- */
-static inline int down_trylock(struct semaphore * sem)
-{
-	int result;
-
-	__asm__ __volatile__(
-		"# atomic interruptible down operation\n\t"
-		"xorl %0,%0\n\t"
-		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
-		"jns 2f\n\t"
-		"lea %1,%%eax\n\t"
-		"call __down_failed_trylock\n\t"
-		"2:\n"
-		:"=&a" (result), "+m" (sem->count)
-		:
-		:"memory");
-	return result;
-}
-
-/*
- * Note! This is subtle. We jump to wake people up only if
- * the semaphore was negative (== somebody was waiting on it).
- */
-static inline void up(struct semaphore * sem)
-{
-	__asm__ __volatile__(
-		"# atomic up operation\n\t"
-		LOCK_PREFIX "incl %0\n\t"     /* ++sem->count */
-		"jg 1f\n\t"
-		"lea %0,%%eax\n\t"
-		"call __up_wakeup\n"
-		"1:"
-		:"+m" (sem->count)
-		:
-		:"memory","ax");
-}
-
-#endif
-#endif
diff --git a/include/asm-x86/semaphore_64.h b/include/asm-x86/semaphore_64.h
deleted file mode 100644
index 79694306bf7..00000000000
--- a/include/asm-x86/semaphore_64.h
+++ /dev/null
@@ -1,180 +0,0 @@
-#ifndef _X86_64_SEMAPHORE_H
-#define _X86_64_SEMAPHORE_H
-
-#include <linux/linkage.h>
-
-#ifdef __KERNEL__
-
-/*
- * SMP- and interrupt-safe semaphores..
- *
- * (C) Copyright 1996 Linus Torvalds
- *
- * Modified 1996-12-23 by Dave Grothe <dave@gcom.com> to fix bugs in
- *                     the original code and to make semaphore waits
- *                     interruptible so that processes waiting on
- *                     semaphores can be killed.
- * Modified 1999-02-14 by Andrea Arcangeli, split the sched.c helper
- *		       functions in asm/sempahore-helper.h while fixing a
- *		       potential and subtle race discovered by Ulrich Schmid
- *		       in down_interruptible(). Since I started to play here I
- *		       also implemented the `trylock' semaphore operation.
- *          1999-07-02 Artur Skawina <skawina@geocities.com>
- *                     Optimized "0(ecx)" -> "(ecx)" (the assembler does not
- *                     do this). Changed calling sequences from push/jmp to
- *                     traditional call/ret.
- * Modified 2001-01-01 Andreas Franck <afranck@gmx.de>
- *		       Some hacks to ensure compatibility with recent
- *		       GCC snapshots, to avoid stack corruption when compiling
- *		       with -fomit-frame-pointer. It's not sure if this will
- *		       be fixed in GCC, as our previous implementation was a
- *		       bit dubious.
- *
- * If you would like to see an analysis of this implementation, please
- * ftp to gcom.com and download the file
- * /pub/linux/src/semaphore/semaphore-2.0.24.tar.gz.
- *
- */
-
-#include <asm/system.h>
-#include <asm/atomic.h>
-#include <asm/rwlock.h>
-#include <linux/wait.h>
-#include <linux/rwsem.h>
-#include <linux/stringify.h>
-
-struct semaphore {
-	atomic_t count;
-	int sleepers;
-	wait_queue_head_t wait;
-};
-
-#define __SEMAPHORE_INITIALIZER(name, n)				\
-{									\
-	.count		= ATOMIC_INIT(n),				\
-	.sleepers	= 0,						\
-	.wait		= __WAIT_QUEUE_HEAD_INITIALIZER((name).wait)	\
-}
-
-#define __DECLARE_SEMAPHORE_GENERIC(name,count) \
-	struct semaphore name = __SEMAPHORE_INITIALIZER(name,count)
-
-#define DECLARE_MUTEX(name) __DECLARE_SEMAPHORE_GENERIC(name,1)
-
-static inline void sema_init (struct semaphore *sem, int val)
-{
-/*
- *	*sem = (struct semaphore)__SEMAPHORE_INITIALIZER((*sem),val);
- *
- * i'd rather use the more flexible initialization above, but sadly
- * GCC 2.7.2.3 emits a bogus warning. EGCS doesn't. Oh well.
- */
-	atomic_set(&sem->count, val);
-	sem->sleepers = 0;
-	init_waitqueue_head(&sem->wait);
-}
-
-static inline void init_MUTEX (struct semaphore *sem)
-{
-	sema_init(sem, 1);
-}
-
-static inline void init_MUTEX_LOCKED (struct semaphore *sem)
-{
-	sema_init(sem, 0);
-}
-
-asmlinkage void __down_failed(void /* special register calling convention */);
-asmlinkage int  __down_failed_interruptible(void  /* params in registers */);
-asmlinkage int  __down_failed_trylock(void  /* params in registers */);
-asmlinkage void __up_wakeup(void /* special register calling convention */);
-
-asmlinkage void __down(struct semaphore * sem);
-asmlinkage int  __down_interruptible(struct semaphore * sem);
-asmlinkage int  __down_trylock(struct semaphore * sem);
-asmlinkage void __up(struct semaphore * sem);
-
-/*
- * This is ugly, but we want the default case to fall through.
- * "__down_failed" is a special asm handler that calls the C
- * routine that actually waits. See arch/x86_64/kernel/semaphore.c
- */
-static inline void down(struct semaphore * sem)
-{
-	might_sleep();
-
-	__asm__ __volatile__(
-		"# atomic down operation\n\t"
-		LOCK_PREFIX "decl %0\n\t"     /* --sem->count */
-		"jns 1f\n\t"
-		"call __down_failed\n"
-		"1:"
-		:"=m" (sem->count)
-		:"D" (sem)
-		:"memory");
-}
-
-/*
- * Interruptible try to acquire a semaphore.  If we obtained
- * it, return zero.  If we were interrupted, returns -EINTR
- */
-static inline int down_interruptible(struct semaphore * sem)
-{
-	int result;
-
-	might_sleep();
-
-	__asm__ __volatile__(
-		"# atomic interruptible down operation\n\t"
-		"xorl %0,%0\n\t"
-		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
-		"jns 2f\n\t"
-		"call __down_failed_interruptible\n"
-		"2:\n"
-		:"=&a" (result), "=m" (sem->count)
-		:"D" (sem)
-		:"memory");
-	return result;
-}
-
-/*
- * Non-blockingly attempt to down() a semaphore.
- * Returns zero if we acquired it
- */
-static inline int down_trylock(struct semaphore * sem)
-{
-	int result;
-
-	__asm__ __volatile__(
-		"# atomic interruptible down operation\n\t"
-		"xorl %0,%0\n\t"
-		LOCK_PREFIX "decl %1\n\t"     /* --sem->count */
-		"jns 2f\n\t"
-		"call __down_failed_trylock\n\t"
-		"2:\n"
-		:"=&a" (result), "=m" (sem->count)
-		:"D" (sem)
-		:"memory","cc");
-	return result;
-}
-
-/*
- * Note! This is subtle. We jump to wake people up only if
- * the semaphore was negative (== somebody was waiting on it).
- * The default case (no contention) will result in NO
- * jumps for both down() and up().
- */
-static inline void up(struct semaphore * sem)
-{
-	__asm__ __volatile__(
-		"# atomic up operation\n\t"
-		LOCK_PREFIX "incl %0\n\t"     /* ++sem->count */
-		"jg 1f\n\t"
-		"call __up_wakeup\n"
-		"1:"
-		:"=m" (sem->count)
-		:"D" (sem)
-		:"memory");
-}
-#endif /* __KERNEL__ */
-#endif