patch-2.2.2 linux/include/asm-i386/semaphore-helper.h

• Lines: 95
• Date: Wed Feb 17 09:34:13 1999
• Orig file: v2.2.1/linux/include/asm-i386/semaphore-helper.h
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.2.1/linux/include/asm-i386/semaphore-helper.h linux/include/asm-i386/semaphore-helper.h
@@ -0,0 +1,94 @@
+#ifndef _I386_SEMAPHORE_HELPER_H
+#define _I386_SEMAPHORE_HELPER_H
+
+/*
+ * SMP- and interrupt-safe semaphores helper functions.
+ *
+ * (C) Copyright 1996 Linus Torvalds
+ * (C) Copyright 1999 Andrea Arcangeli
+ */
+
+/*
+ * These two _must_ execute atomically wrt each other.
+ *
+ * This is trivially done with load_locked/store_cond,
+ * but on the x86 we need an external synchronizer.
+ */
+static inline void wake_one_more(struct semaphore * sem)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&semaphore_wake_lock, flags);
+	if (atomic_read(&sem->count) <= 0)
+		sem->waking++;
+	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
+}
+
+static inline int waking_non_zero(struct semaphore *sem)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&semaphore_wake_lock, flags);
+	if (sem->waking > 0) {
+		sem->waking--;
+		ret = 1;
+	}
+	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
+	return ret;
+}
+
+/*
+ * waking_non_zero_interruptible:
+ *	1	got the lock
+ *	0	go to sleep
+ *	-EINTR	interrupted
+ *
+ * We must undo the sem->count down_interruptible() increment while we are
+ * protected by the spinlock in order to make atomic this atomic_inc() with the
+ * atomic_read() in wake_one_more(), otherwise we can race. -arca
+ */
+static inline int waking_non_zero_interruptible(struct semaphore *sem,
+						struct task_struct *tsk)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&semaphore_wake_lock, flags);
+	if (sem->waking > 0) {
+		sem->waking--;
+		ret = 1;
+	} else if (signal_pending(tsk)) {
+		atomic_inc(&sem->count);
+		ret = -EINTR;
+	}
+	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
+	return ret;
+}
+
+/*
+ * waking_non_zero_trylock:
+ *	1	failed to lock
+ *	0	got the lock
+ *
+ * We must undo the sem->count down_trylock() increment while we are
+ * protected by the spinlock in order to make atomic this atomic_inc() with the
+ * atomic_read() in wake_one_more(), otherwise we can race. -arca
+ */
+static inline int waking_non_zero_trylock(struct semaphore *sem)
+{
+	unsigned long flags;
+	int ret = 1;
+
+	spin_lock_irqsave(&semaphore_wake_lock, flags);
+	if (sem->waking <= 0)
+		atomic_inc(&sem->count);
+	else {
+		sem->waking--;
+		ret = 0;
+	}
+	spin_unlock_irqrestore(&semaphore_wake_lock, flags);
+	return ret;
+}
+
+#endif