diff -r 374f6ed5f63c sys/kern/sys_futex.c
--- a/sys/kern/sys_futex.c	Fri Apr 17 18:26:28 2020 +0200
+++ b/sys/kern/sys_futex.c	Mon Apr 27 20:09:22 2020 +0000
@@ -864,7 +864,9 @@ static void
 futex_wait_abort(struct futex_wait *fw)
 {
 	struct futex *f;
+	bool restart;
 
+restart:
 	/* Acquire fw_lock so that the content of fw won't change.  */
 	mutex_enter(&fw->fw_lock);
 
@@ -883,9 +885,21 @@ futex_wait_abort(struct futex_wait *fw)
 	/* f is now stable, so we can release fw_lock.  */
 	mutex_exit(&fw->fw_lock);
 
-	/* Now we can remove fw under the queue lock.  */
+	/*
+	 * Now we can remove fw under the queue lock.  However, if,
+	 * while we dropped both locks, anyone issued futex_wake --
+	 * moving us off f and possibly onto a different futex -- then
+	 * we have to start over.
+	 */
 	mutex_enter(&f->fx_qlock);
-	TAILQ_REMOVE(&f->fx_queue, fw, fw_entry);
+	mutex_enter(&fw->fw_lock);
+	if (fw->fw_futex != f) {
+		restart = true;
+	} else {
+		futex_wait_dequeue(fw, f);
+		restart = false;
+	}
+	mutex_exit(&fw->fw_lock);
 	mutex_exit(&f->fx_qlock);
 
 	/*
@@ -897,6 +911,10 @@ futex_wait_abort(struct futex_wait *fw)
 	if (LIST_EMPTY(&f->fx_abortlist))
 		cv_broadcast(&f->fx_abortcv);
 	mutex_exit(&f->fx_abortlock);
+
+	/* If we were too late, try again.  */
+	if (restart)
+		goto restart;
 }
 
 /*