This commit was manufactured by cvs2svn to create branch 'vserver'.

[linux-2.6.git] / arch / frv / kernel / semaphore.c

diff --git a/arch/frv/kernel/semaphore.c b/arch/frv/kernel/semaphore.c
new file mode 100644 (file)
index 0000000..5cba9c1
--- /dev/null
+++ b/arch/frv/kernel/semaphore.c
@@ -0,0 +1,156 @@
+/* semaphore.c: FR-V semaphores
+ *
+ * Copyright (C) 2003 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ * - Derived from lib/rwsem-spinlock.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/config.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <asm/semaphore.h>
+
+struct sem_waiter {
+       struct list_head        list;
+       struct task_struct      *task;
+};
+
+#if SEM_DEBUG
+void semtrace(struct semaphore *sem, const char *str)
+{
+       if (sem->debug)
+               printk("[%d] %s({%d,%d})\n",
+                      current->pid,
+                      str,
+                      sem->counter,
+                      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 (list_empty(&waiter.list))
+                       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 (list_empty(&waiter.list))
+                       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);
+
+       if (!list_empty(&waiter.list)) {
+               list_del(&waiter.list);
+               ret = -EINTR;
+       }
+
+       spin_unlock_irqrestore(&sem->wait_lock, flags);
+       if (ret == -EINTR)
+               put_task_struct(current);
+       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;
+       mb();
+       waiter->task = NULL;
+       wake_up_process(tsk);
+       put_task_struct(tsk);
+
+       semtrace(sem,"Leaving __up");
+}
+
+EXPORT_SYMBOL(__up);