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>

2 files changed, 1 insertions, 150 deletions

diff --git a/arch/mn10300/kernel/Makefile b/arch/mn10300/kernel/Makefile
index ef07c956170..23f2ab67574 100644
--- a/arch/mn10300/kernel/Makefile
+++ b/arch/mn10300/kernel/Makefile
@@ -3,7 +3,7 @@
 #
 extra-y := head.o init_task.o vmlinux.lds
 
-obj-y   := process.o semaphore.o signal.o entry.o fpu.o traps.o irq.o \
+obj-y   := process.o signal.o entry.o fpu.o traps.o irq.o \
 	   ptrace.o setup.o time.o sys_mn10300.o io.o kthread.o \
 	   switch_to.o mn10300_ksyms.o kernel_execve.o
 
diff --git a/arch/mn10300/kernel/semaphore.c b/arch/mn10300/kernel/semaphore.c
deleted file mode 100644
index 9153c4039fd..00000000000
--- a/arch/mn10300/kernel/semaphore.c
+++ /dev/null
@@ -1,149 +0,0 @@
-/* MN10300 Semaphore implementation
- *
- * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
- * Written by David Howells (dhowells@redhat.com)
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
- * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
- */
-#include <linux/sched.h>
-#include <linux/module.h>
-#include <asm/semaphore.h>
-
-struct sem_waiter {
-	struct list_head	list;
-	struct task_struct	*task;
-};
-
-#if SEMAPHORE_DEBUG
-void semtrace(struct semaphore *sem, const char *str)
-{
-	if (sem->debug)
-		printk(KERN_DEBUG "[%d] %s({%d,%d})\n",
-		       current->pid,
-		       str,
-		       atomic_read(&sem->count),
-		       list_empty(&sem->wait_list) ? 0 : 1);
-}
-#else
-#define semtrace(SEM, STR) do { } while (0)
-#endif
-
-/*
- * wait for a token to be granted from a semaphore
- * - entered with lock held and interrupts disabled
- */
-void __down(struct semaphore *sem, unsigned long flags)
-{
-	struct task_struct *tsk = current;
-	struct sem_waiter waiter;
-
-	semtrace(sem, "Entering __down");
-
-	/* set up my own style of waitqueue */
-	waiter.task = tsk;
-	get_task_struct(tsk);
-
-	list_add_tail(&waiter.list, &sem->wait_list);
-
-	/* we don't need to touch the semaphore struct anymore */
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
-
-	/* wait to be given the semaphore */
-	set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-
-	for (;;) {
-		if (!waiter.task)
-			break;
-		schedule();
-		set_task_state(tsk, TASK_UNINTERRUPTIBLE);
-	}
-
-	tsk->state = TASK_RUNNING;
-	semtrace(sem, "Leaving __down");
-}
-EXPORT_SYMBOL(__down);
-
-/*
- * interruptibly wait for a token to be granted from a semaphore
- * - entered with lock held and interrupts disabled
- */
-int __down_interruptible(struct semaphore *sem, unsigned long flags)
-{
-	struct task_struct *tsk = current;
-	struct sem_waiter waiter;
-	int ret;
-
-	semtrace(sem, "Entering __down_interruptible");
-
-	/* set up my own style of waitqueue */
-	waiter.task = tsk;
-	get_task_struct(tsk);
-
-	list_add_tail(&waiter.list, &sem->wait_list);
-
-	/* we don't need to touch the semaphore struct anymore */
-	set_task_state(tsk, TASK_INTERRUPTIBLE);
-
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
-
-	/* wait to be given the semaphore */
-	ret = 0;
-	for (;;) {
-		if (!waiter.task)
-			break;
-		if (unlikely(signal_pending(current)))
-			goto interrupted;
-		schedule();
-		set_task_state(tsk, TASK_INTERRUPTIBLE);
-	}
-
- out:
-	tsk->state = TASK_RUNNING;
-	semtrace(sem, "Leaving __down_interruptible");
-	return ret;
-
- interrupted:
-	spin_lock_irqsave(&sem->wait_lock, flags);
-	list_del(&waiter.list);
-	spin_unlock_irqrestore(&sem->wait_lock, flags);
-
-	ret = 0;
-	if (!waiter.task) {
-		put_task_struct(current);
-		ret = -EINTR;
-	}
-	goto out;
-}
-EXPORT_SYMBOL(__down_interruptible);
-
-/*
- * release a single token back to a semaphore
- * - entered with lock held and interrupts disabled
- */
-void __up(struct semaphore *sem)
-{
-	struct task_struct *tsk;
-	struct sem_waiter *waiter;
-
-	semtrace(sem, "Entering __up");
-
-	/* grant the token to the process at the front of the queue */
-	waiter = list_entry(sem->wait_list.next, struct sem_waiter, list);
-
-	/* We must be careful not to touch 'waiter' after we set ->task = NULL.
-	 * It is an allocated on the waiter's stack and may become invalid at
-	 * any time after that point (due to a wakeup from another source).
-	 */
-	list_del_init(&waiter->list);
-	tsk = waiter->task;
-	smp_mb();
-	waiter->task = NULL;
-	wake_up_process(tsk);
-	put_task_struct(tsk);
-
-	semtrace(sem, "Leaving __up");
-}
-EXPORT_SYMBOL(__up);