CVS commit: src/lib/libpthread

[Andrew Doran]

Module Name:    src
Committed By:   ad
Date:           Sat Jan 25 18:01:28 UTC 2020

Modified Files:
        src/lib/libpthread: pthread.c

Log Message:
pthread_exit(): it looks there there is at least one path through which
a thread can exit with waiters still hanging off it (cancellation when
waiting on a condvar) so deal with all/any crappy failure like that and
make sure there are never any waiters left before exiting.  Maybe of help
for:

PR: bin/50350: rump/rumpkern/t_sp/stress_{long,short} fail on Core 2


To generate a diff of this commit:
cvs rdiff -u -r1.155 -r1.156 src/lib/libpthread/pthread.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.


Modified files:

Index: src/lib/libpthread/pthread.c
diff -u src/lib/libpthread/pthread.c:1.155 src/lib/libpthread/pthread.c:1.156
--- src/lib/libpthread/pthread.c:1.155	Sat Jan 25 15:41:52 2020
+++ src/lib/libpthread/pthread.c	Sat Jan 25 18:01:28 2020
@@ -1,4 +1,4 @@
-/*	$NetBSD: pthread.c,v 1.155 2020/01/25 15:41:52 ad Exp $	*/
+/*	$NetBSD: pthread.c,v 1.156 2020/01/25 18:01:28 ad Exp $	*/
 
 /*-
  * Copyright (c) 2001, 2002, 2003, 2006, 2007, 2008, 2020
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: pthread.c,v 1.155 2020/01/25 15:41:52 ad Exp $");
+__RCSID("$NetBSD: pthread.c,v 1.156 2020/01/25 18:01:28 ad Exp $");
 
 #define	__EXPOSE_STACK	1
 
@@ -621,6 +621,23 @@ pthread_resume_np(pthread_t thread)
 	return errno;
 }
 
+/*
+ * In case the thread is exiting at an inopportune time leaving waiters not
+ * awoken (because cancelled, for instance) make sure we have no waiters
+ * left.
+ */
+static void
+pthread__clear_waiters(pthread_t self)
+{
+
+	if (self->pt_nwaiters != 0) {
+		(void)_lwp_unpark_all(self->pt_waiters, self->pt_nwaiters,
+		    NULL);
+		self->pt_nwaiters = 0;
+	}
+	self->pt_willpark = 0;
+}
+
 void
 pthread_exit(void *retval)
 {
@@ -658,7 +675,10 @@ pthread_exit(void *retval)
 	/* Perform cleanup of thread-specific data */
 	pthread__destroy_tsd(self);
 
-	/* Signal our exit. */
+	/*
+	 * Signal our exit.  Our stack and pthread_t won't be reused until
+	 * pthread_create() can see from kernel info that this LWP is gone.
+	 */
 	self->pt_exitval = retval;
 	if (self->pt_flags & PT_FLAG_DETACHED) {
 		self->pt_state = PT_STATE_DEAD;
@@ -670,11 +690,13 @@ pthread_exit(void *retval)
 		pthread_mutex_lock(&pthread__deadqueue_lock);
 		PTQ_INSERT_TAIL(&pthread__deadqueue, self, pt_deadq);
 		pthread_mutex_unlock(&pthread__deadqueue_lock);
+		pthread__clear_waiters(self);
 		_lwp_exit();
 	} else {
 		self->pt_state = PT_STATE_ZOMBIE;
 		pthread_cond_broadcast(&self->pt_joiners);
 		pthread_mutex_unlock(&self->pt_lock);
+		pthread__clear_waiters(self);
 		/* Note: name will be freed by the joiner. */
 		_lwp_exit();
 	}