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===================================================================
RCS file: /ftp/cvs/cvsroot/src/lib/libpthread/pthread_lock.c,v
rcsdiff: /ftp/cvs/cvsroot/src/lib/libpthread/pthread_lock.c,v: warning: Unknown phrases like `commitid ...;' are present.
retrieving revision 1.1
retrieving revision 1.1.2.4
diff -u -p -r1.1 -r1.1.2.4
--- src/lib/libpthread/pthread_lock.c	2001/03/05 23:51:56	1.1
+++ src/lib/libpthread/pthread_lock.c	2001/07/20 21:23:53	1.1.2.4
@@ -0,0 +1,137 @@
+/*	$NetBSD: pthread_lock.c,v 1.1.2.4 2001/07/20 21:23:53 nathanw Exp $	*/
+
+/*-
+ * Copyright (c) 2001 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Nathan J. Williams.
+ *
+ * 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. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *        This product includes software developed by the NetBSD
+ *        Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
+ */
+
+#include "pthread.h"
+#include "pthread_int.h"
+
+/* How many times to try before checking whether we've been continued. */
+#define NSPINS 20	/* XXX arbitrary */
+
+static int nspins = NSPINS;
+
+void
+pthread_lockinit(pt_spin_t *lock)
+{
+
+	__cpu_simple_lock_init(lock);
+}
+
+void
+pthread_spinlock(pthread_t thread, pt_spin_t *lock)
+{
+	int count, ret;
+
+	count = nspins;
+	++thread->pt_spinlocks;
+
+	do {
+		while (((ret = __cpu_simple_lock_try(lock)) == 0) && --count)
+			;
+
+		if (ret == 1)
+			break;
+		
+		--thread->pt_spinlocks;
+			
+		/* We may be preempted while spinning. If so, we will
+		 * be restarted here if thread->pt_spinlocks is
+		 * nonzero, which can happen if:
+		 * a) we just got the lock
+		 * b) we haven't yet decremented the lock count.
+		 * If we're at this point, (b) applies. Therefore,
+		 * check if we're being continued, and if so, bail.
+		 * (in case (a), we should let the code finish and 
+		 * we will bail out in pthread_spinunlock()).
+		 */
+		if (thread->pt_next != NULL) {
+			PTHREADD_ADD(PTHREADD_SPINPREEMPT);
+			pthread__switch(thread, thread->pt_next, 0);
+		}
+		/* try again */
+		count = nspins;
+		++thread->pt_spinlocks;
+	} while (/*CONSTCOND*/1);
+
+	PTHREADD_ADD(PTHREADD_SPINLOCKS);
+	/* Got it! We're out of here. */
+}
+
+
+int
+pthread_spintrylock(pthread_t thread, pt_spin_t *lock)
+{
+	int ret;
+
+	++thread->pt_spinlocks;
+
+	ret = __cpu_simple_lock_try(lock);
+	
+	if (ret == 0) {
+		--thread->pt_spinlocks;
+		/* See above. */
+		if (thread->pt_next != NULL) {
+			PTHREADD_ADD(PTHREADD_SPINPREEMPT);
+			pthread__switch(thread, thread->pt_next, 0);
+		}
+	}
+
+	return ret;
+}
+
+
+void
+pthread_spinunlock(pthread_t thread, pt_spin_t *lock)
+{
+	__cpu_simple_unlock(lock);
+	--thread->pt_spinlocks;
+
+	PTHREADD_ADD(PTHREADD_SPINUNLOCKS);
+
+	/* If we were preempted while holding a spinlock, the
+	 * scheduler will notice this and continue us. To be good
+	 * citzens, we must now get out of here if that was our
+	 * last spinlock.
+	 * XXX when will we ever have more than one?
+	 */
+	
+	if ((thread->pt_spinlocks == 0) && (thread->pt_next != NULL)) {
+		PTHREADD_ADD(PTHREADD_SPINPREEMPT);
+		pthread__switch(thread, thread->pt_next, 0);
+	}
+}
+