Initial Spring 2016 commit.

kern/include/wchan.h

@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
+ *	The President and Fellows of Harvard College.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef _WCHAN_H_
+#define _WCHAN_H_
+
+/*
+ * Wait channel.
+ */
+
+
+struct spinlock; /* in spinlock.h */
+struct wchan; /* Opaque */
+
+/*
+ * Create a wait channel. Use NAME as a symbolic name for the channel.
+ * NAME should be a string constant; if not, the caller is responsible
+ * for freeing it after the wchan is destroyed.
+ */
+struct wchan *wchan_create(const char *name);
+
+/*
+ * Destroy a wait channel. Must be empty and unlocked.
+ */
+void wchan_destroy(struct wchan *wc);
+
+/*
+ * Return nonzero if there are no threads sleeping on the channel.
+ * This is meant to be used only for diagnostic purposes.
+ */
+bool wchan_isempty(struct wchan *wc, struct spinlock *lk);
+
+/*
+ * Go to sleep on a wait channel. The current thread is suspended
+ * until awakened by someone else, at which point this function
+ * returns.
+ *
+ * The associated lock must be locked. It will be unlocked while
+ * sleeping, and relocked upon return.
+ */
+void wchan_sleep(struct wchan *wc, struct spinlock *lk);
+
+/*
+ * Wake up one thread, or all threads, sleeping on a wait channel.
+ * The associated spinlock should be locked.
+ *
+ * The current implementation is FIFO but this is not promised by the
+ * interface.
+ */
+void wchan_wakeone(struct wchan *wc, struct spinlock *lk);
+void wchan_wakeall(struct wchan *wc, struct spinlock *lk);
+
+
+#endif /* _WCHAN_H_ */