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>

5 files changed, 2 insertions, 193 deletions

diff --git a/arch/m68k/kernel/Makefile b/arch/m68k/kernel/Makefile
index a806208c7fb..7a62a718143 100644
--- a/arch/m68k/kernel/Makefile
+++ b/arch/m68k/kernel/Makefile
@@ -10,7 +10,7 @@ endif
 extra-y	+= vmlinux.lds
 
 obj-y	:= entry.o process.o traps.o ints.o signal.o ptrace.o module.o \
-	   sys_m68k.o time.o semaphore.o setup.o m68k_ksyms.o devres.o
+	   sys_m68k.o time.o setup.o m68k_ksyms.o devres.o
 
 devres-y = ../../../kernel/irq/devres.o
 
diff --git a/arch/m68k/kernel/m68k_ksyms.c b/arch/m68k/kernel/m68k_ksyms.c
index 6fc69c74fe2..d900e77e536 100644
--- a/arch/m68k/kernel/m68k_ksyms.c
+++ b/arch/m68k/kernel/m68k_ksyms.c
@@ -1,5 +1,4 @@
 #include <linux/module.h>
-#include <asm/semaphore.h>
 
 asmlinkage long long __ashldi3 (long long, int);
 asmlinkage long long __ashrdi3 (long long, int);
@@ -15,8 +14,3 @@ EXPORT_SYMBOL(__ashrdi3);
 EXPORT_SYMBOL(__lshrdi3);
 EXPORT_SYMBOL(__muldi3);
 
-EXPORT_SYMBOL(__down_failed);
-EXPORT_SYMBOL(__down_failed_interruptible);
-EXPORT_SYMBOL(__down_failed_trylock);
-EXPORT_SYMBOL(__up_wakeup);
-
diff --git a/arch/m68k/kernel/semaphore.c b/arch/m68k/kernel/semaphore.c
deleted file mode 100644
index d12cbbfe6eb..00000000000
--- a/arch/m68k/kernel/semaphore.c
+++ /dev/null
@@ -1,132 +0,0 @@
-/*
- *  Generic semaphore code. Buyer beware. Do your own
- * specific changes in <asm/semaphore-helper.h>
- */
-
-#include <linux/sched.h>
-#include <linux/init.h>
-#include <asm/semaphore-helper.h>
-
-#ifndef CONFIG_RMW_INSNS
-spinlock_t semaphore_wake_lock;
-#endif
-
-/*
- * Semaphores are implemented using a two-way counter:
- * The "count" variable is decremented for each process
- * that tries to sleep, while the "waking" variable is
- * incremented when the "up()" code goes to wake up waiting
- * processes.
- *
- * Notably, the inline "up()" and "down()" functions can
- * efficiently test if they need to do any extra work (up
- * needs to do something only if count was negative before
- * the increment operation.
- *
- * waking_non_zero() (from asm/semaphore.h) must execute
- * atomically.
- *
- * When __up() is called, the count was negative before
- * incrementing it, and we need to wake up somebody.
- *
- * This routine adds one to the count of processes that need to
- * wake up and exit.  ALL waiting processes actually wake up but
- * only the one that gets to the "waking" field first will gate
- * through and acquire the semaphore.  The others will go back
- * to sleep.
- *
- * 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)
-{
-	wake_one_more(sem);
-	wake_up(&sem->wait);
-}
-
-/*
- * Perform the "down" function.  Return zero for semaphore acquired,
- * return negative for signalled out of the function.
- *
- * If called from __down, the return is ignored and the wait loop is
- * not interruptible.  This means that a task waiting on a semaphore
- * using "down()" cannot be killed until someone does an "up()" on
- * the semaphore.
- *
- * If called from __down_interruptible, the return value gets checked
- * upon return.  If the return value is negative then the task continues
- * with the negative value in the return register (it can be tested by
- * the caller).
- *
- * Either form may be used in conjunction with "up()".
- *
- */
-
-
-#define DOWN_HEAD(task_state)						\
-									\
-									\
-	current->state = (task_state);					\
-	add_wait_queue(&sem->wait, &wait);				\
-									\
-	/*								\
-	 * Ok, we're set up.  sem->count is known to be less than zero	\
-	 * so we must wait.						\
-	 *								\
-	 * We can let go the lock for purposes of waiting.		\
-	 * We re-acquire it after awaking so as to protect		\
-	 * all semaphore operations.					\
-	 *								\
-	 * If "up()" is called before we call waking_non_zero() then	\
-	 * we will catch it right away.  If it is called later then	\
-	 * we will have to go through a wakeup cycle to catch it.	\
-	 *								\
-	 * Multiple waiters contend for the semaphore lock to see	\
-	 * who gets to gate through and who has to wait some more.	\
-	 */								\
-	for (;;) {
-
-#define DOWN_TAIL(task_state)			\
-		current->state = (task_state);	\
-	}					\
-	current->state = TASK_RUNNING;		\
-	remove_wait_queue(&sem->wait, &wait);
-
-void __sched __down(struct semaphore * sem)
-{
-	DECLARE_WAITQUEUE(wait, current);
-
-	DOWN_HEAD(TASK_UNINTERRUPTIBLE)
-	if (waking_non_zero(sem))
-		break;
-	schedule();
-	DOWN_TAIL(TASK_UNINTERRUPTIBLE)
-}
-
-int __sched __down_interruptible(struct semaphore * sem)
-{
-	DECLARE_WAITQUEUE(wait, current);
-	int ret = 0;
-
-	DOWN_HEAD(TASK_INTERRUPTIBLE)
-
-	ret = waking_non_zero_interruptible(sem, current);
-	if (ret)
-	{
-		if (ret == 1)
-			/* ret != 0 only if we get interrupted -arca */
-			ret = 0;
-		break;
-	}
-	schedule();
-	DOWN_TAIL(TASK_INTERRUPTIBLE)
-	return ret;
-}
-
-int __down_trylock(struct semaphore * sem)
-{
-	return waking_non_zero_trylock(sem);
-}
diff --git a/arch/m68k/lib/Makefile b/arch/m68k/lib/Makefile
index 6bbf19f9600..a18af095cd7 100644
--- a/arch/m68k/lib/Makefile
+++ b/arch/m68k/lib/Makefile
@@ -5,4 +5,4 @@
 EXTRA_AFLAGS := -traditional
 
 lib-y	:= ashldi3.o ashrdi3.o lshrdi3.o muldi3.o \
-	   checksum.o string.o semaphore.o uaccess.o
+	   checksum.o string.o uaccess.o
diff --git a/arch/m68k/lib/semaphore.S b/arch/m68k/lib/semaphore.S
deleted file mode 100644
index 0215624c160..00000000000
--- a/arch/m68k/lib/semaphore.S
+++ /dev/null
@@ -1,53 +0,0 @@
-/*
- *  linux/arch/m68k/lib/semaphore.S
- *
- *  Copyright (C) 1996  Linus Torvalds
- *
- *  m68k version by Andreas Schwab
- */
-
-#include <linux/linkage.h>
-#include <asm/semaphore.h>
-
-/*
- * The semaphore operations have a special calling sequence that
- * allow us to do a simpler in-line version of them. These routines
- * need to convert that sequence back into the C sequence when
- * there is contention on the semaphore.
- */
-ENTRY(__down_failed)
-	moveml %a0/%d0/%d1,-(%sp)
-	movel %a1,-(%sp)
-	jbsr __down
-	movel (%sp)+,%a1
-	moveml (%sp)+,%a0/%d0/%d1
-	rts
-
-ENTRY(__down_failed_interruptible)
-	movel %a0,-(%sp)
-	movel %d1,-(%sp)
-	movel %a1,-(%sp)
-	jbsr __down_interruptible
-	movel (%sp)+,%a1
-	movel (%sp)+,%d1
-	movel (%sp)+,%a0
-	rts
-
-ENTRY(__down_failed_trylock)
-	movel %a0,-(%sp)
-	movel %d1,-(%sp)
-	movel %a1,-(%sp)
-	jbsr __down_trylock
-	movel (%sp)+,%a1
-	movel (%sp)+,%d1
-	movel (%sp)+,%a0
-	rts
-
-ENTRY(__up_wakeup)
-	moveml %a0/%d0/%d1,-(%sp)
-	movel %a1,-(%sp)
-	jbsr __up
-	movel (%sp)+,%a1
-	moveml (%sp)+,%a0/%d0/%d1
-	rts
-