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, 207 deletions

diff --git a/arch/m68knommu/kernel/Makefile b/arch/m68knommu/kernel/Makefile
index 1524b39..f0eab3d 100644
--- a/arch/m68knommu/kernel/Makefile
+++ b/arch/m68knommu/kernel/Makefile
@@ -5,7 +5,7 @@
 extra-y := vmlinux.lds
 
 obj-y += dma.o entry.o init_task.o irq.o m68k_ksyms.o process.o ptrace.o \
-	 semaphore.o setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o
+	 setup.o signal.o syscalltable.o sys_m68k.o time.o traps.o
 
 obj-$(CONFIG_MODULES)	+= module.o
 obj-$(CONFIG_COMEMPCI)	+= comempci.o
diff --git a/arch/m68knommu/kernel/m68k_ksyms.c b/arch/m68knommu/kernel/m68k_ksyms.c
index 53fad14..39fe0a7 100644
--- a/arch/m68knommu/kernel/m68k_ksyms.c
+++ b/arch/m68knommu/kernel/m68k_ksyms.c
@@ -13,7 +13,6 @@
 #include <asm/pgalloc.h>
 #include <asm/irq.h>
 #include <asm/io.h>
-#include <asm/semaphore.h>
 #include <asm/checksum.h>
 #include <asm/current.h>
 
@@ -39,11 +38,6 @@ EXPORT_SYMBOL(csum_partial_copy_nocheck);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memset);
 
-EXPORT_SYMBOL(__down_failed);
-EXPORT_SYMBOL(__down_failed_interruptible);
-EXPORT_SYMBOL(__down_failed_trylock);
-EXPORT_SYMBOL(__up_wakeup);
-
 /*
  * libgcc functions - functions that are used internally by the
  * compiler...  (prototypes are not correct though, but that
diff --git a/arch/m68knommu/kernel/semaphore.c b/arch/m68knommu/kernel/semaphore.c
deleted file mode 100644
index bce2bc7..0000000
--- a/arch/m68knommu/kernel/semaphore.c
+++ /dev/null
@@ -1,133 +0,0 @@
-/*
- *  Generic semaphore code. Buyer beware. Do your own
- * specific changes in <asm/semaphore-helper.h>
- */
-
-#include <linux/sched.h>
-#include <linux/err.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/m68knommu/lib/Makefile b/arch/m68knommu/lib/Makefile
index e051a79..d94d709 100644
--- a/arch/m68knommu/lib/Makefile
+++ b/arch/m68knommu/lib/Makefile
@@ -4,4 +4,4 @@
 
 lib-y	:= ashldi3.o ashrdi3.o lshrdi3.o \
 	   muldi3.o mulsi3.o divsi3.o udivsi3.o modsi3.o umodsi3.o \
-	   checksum.o semaphore.o memcpy.o memset.o delay.o
+	   checksum.o memcpy.o memset.o delay.o
diff --git a/arch/m68knommu/lib/semaphore.S b/arch/m68knommu/lib/semaphore.S
deleted file mode 100644
index 87c7460..0000000
--- a/arch/m68knommu/lib/semaphore.S
+++ /dev/null
@@ -1,66 +0,0 @@
-/*
- *  linux/arch/m68k/lib/semaphore.S
- *
- *  Copyright (C) 1996  Linus Torvalds
- *
- *  m68k version by Andreas Schwab
- *
- *  MAR/1999 -- modified to support ColdFire (gerg@snapgear.com)
- */
-
-#include <linux/linkage.h>
-#include <asm/semaphore.h>
-
-/*
- * "down_failed" is called with the eventual return address
- * in %a0, and the address of the semaphore in %a1. We need
- * to increment the number of waiters on the semaphore,
- * call "__down()", and then eventually return to try again.
- */
-ENTRY(__down_failed)
-#ifdef CONFIG_COLDFIRE
-	subl #12,%sp
-	moveml %a0/%d0/%d1,(%sp)
-#else
-	moveml %a0/%d0/%d1,-(%sp)
-#endif
-	movel %a1,-(%sp)
-	jbsr __down
-	movel (%sp)+,%a1
-	movel (%sp)+,%d0
-	movel (%sp)+,%d1
-	rts
-
-ENTRY(__down_failed_interruptible)
-	movel %a0,-(%sp)
-	movel %d1,-(%sp)
-	movel %a1,-(%sp)
-	jbsr __down_interruptible
-	movel (%sp)+,%a1
-	movel (%sp)+,%d1
-	rts
-
-ENTRY(__up_wakeup)
-#ifdef CONFIG_COLDFIRE
-	subl #12,%sp
-	moveml %a0/%d0/%d1,(%sp)
-#else
-	moveml %a0/%d0/%d1,-(%sp)
-#endif
-	movel %a1,-(%sp)
-	jbsr __up
-	movel (%sp)+,%a1
-	movel (%sp)+,%d0
-	movel (%sp)+,%d1
-	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
-