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 ef07c956170a..23f2ab67574c 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 9153c4039fd2..000000000000
--- 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);