diff --git a/cmd/ztest/ztest.c b/cmd/ztest/ztest.c
index 69086a34a2..5706055216 100644
--- a/cmd/ztest/ztest.c
+++ b/cmd/ztest/ztest.c
@@ -4904,21 +4904,12 @@ ztest_resume_thread(void *arg)
 	return (NULL);
 }
 
-static void *
-ztest_deadman_thread(void *arg)
+#define GRACE	300
+
+static void
+ztest_deadman_alarm(int sig)
 {
-	ztest_shared_t *zs = arg;
-	int grace = 300;
-	hrtime_t delta;
-
-	delta = (zs->zs_thread_stop - zs->zs_thread_start) / NANOSEC + grace;
-
-	(void) poll(NULL, 0, (int)(1000 * delta));
-
-	fatal(0, "failed to complete within %d seconds of deadline", grace);
-	thread_exit();
-
-	return (NULL);
+	fatal(0, "failed to complete within %d seconds of deadline", GRACE);
 }
 
 static void
@@ -5106,7 +5097,7 @@ ztest_dataset_close(ztest_shared_t *zs, int d)
 static void
 ztest_run(ztest_shared_t *zs)
 {
-	kthread_t **tid;
+	kt_did_t *tid;
 	spa_t *spa;
 	kthread_t *resume_thread;
 	uint64_t object;
@@ -5158,10 +5149,10 @@ ztest_run(ztest_shared_t *zs)
 	    spa, TS_RUN, NULL, 0, 0)), !=, NULL);
 
 	/*
-	 * Create a deadman thread to abort() if we hang.
+	 * Set a deadman alarm to abort() if we hang.
 	 */
-	VERIFY3P(thread_create(NULL, 0, ztest_deadman_thread, zs,
-	    TS_RUN, NULL, 0, 0), !=, NULL);
+	signal(SIGALRM, ztest_deadman_alarm);
+	alarm((zs->zs_thread_stop - zs->zs_thread_start) / NANOSEC + GRACE);
 
 	/*
 	 * Verify that we can safely inquire about about any object,
@@ -5187,7 +5178,7 @@ ztest_run(ztest_shared_t *zs)
 	}
 	zs->zs_enospc_count = 0;
 
-	tid = umem_zalloc(zopt_threads * sizeof (kthread_t *), UMEM_NOFAIL);
+	tid = umem_zalloc(zopt_threads * sizeof (kt_did_t), UMEM_NOFAIL);
 
 	if (zopt_verbose >= 4)
 		(void) printf("starting main threads...\n");
@@ -5196,11 +5187,14 @@ ztest_run(ztest_shared_t *zs)
 	 * Kick off all the tests that run in parallel.
 	 */
 	for (int t = 0; t < zopt_threads; t++) {
+		kthread_t *thread;
+
 		if (t < zopt_datasets && ztest_dataset_open(zs, t) != 0)
 			return;
 
-		VERIFY3P(tid[t] = thread_create(NULL, 0, ztest_thread,
+		VERIFY3P(thread = thread_create(NULL, 0, ztest_thread,
 		    (void *)(uintptr_t)t, TS_RUN, NULL, 0, 0), !=, NULL);
+		tid[t] = thread->t_tid;
 	}
 
 	/*
@@ -5208,7 +5202,7 @@ ztest_run(ztest_shared_t *zs)
 	 * so we don't close datasets while threads are still using them.
 	 */
 	for (int t = zopt_threads - 1; t >= 0; t--) {
-		thread_join(tid[t]->t_tid);
+		thread_join(tid[t]);
 		if (t < zopt_datasets)
 			ztest_dataset_close(zs, t);
 	}
@@ -5218,7 +5212,7 @@ ztest_run(ztest_shared_t *zs)
 	zs->zs_alloc = metaslab_class_get_alloc(spa_normal_class(spa));
 	zs->zs_space = metaslab_class_get_space(spa_normal_class(spa));
 
-	umem_free(tid, zopt_threads * sizeof (kthread_t *));
+	umem_free(tid, zopt_threads * sizeof (kt_did_t));
 
 	/* Kill the resume thread */
 	ztest_exiting = B_TRUE;
diff --git a/lib/libzpool/include/sys/zfs_context.h b/lib/libzpool/include/sys/zfs_context.h
index afca6364db..c104f6d3a1 100644
--- a/lib/libzpool/include/sys/zfs_context.h
+++ b/lib/libzpool/include/sys/zfs_context.h
@@ -203,7 +203,8 @@ _NOTE(CONSTCOND) } while (0)
 /*
  * Threads
  */
-#define TS_RUN			0x00000002
+#define	TS_MAGIC		0x72f158ab4261e538ull
+#define	TS_RUN			0x00000002
 #ifdef _linux_
 #define	STACK_SIZE		8192	/* Linux x86 and amd64 */
 #else
@@ -227,7 +228,6 @@ typedef struct kthread {
 	void *		t_arg;
 } kthread_t;
 
-/* XXX tsd_create()/tsd_destroy() missing */
 #define	tsd_get(key)			pthread_getspecific(key)
 #define	tsd_set(key, val)		pthread_setspecific(key, val)
 #define	curthread			zk_thread_current()
diff --git a/lib/libzpool/kernel.c b/lib/libzpool/kernel.c
index 27a99cc26c..ebc979dc8c 100644
--- a/lib/libzpool/kernel.c
+++ b/lib/libzpool/kernel.c
@@ -191,13 +191,16 @@ zk_thread_exit(void)
 	pthread_mutex_unlock(&kthread_lock);
 
 	pthread_cond_broadcast(&kthread_cond);
-	pthread_exit(NULL);
+	pthread_exit((void *)TS_MAGIC);
 }
 
 void
 zk_thread_join(kt_did_t tid)
 {
-	pthread_join((pthread_t)tid, NULL);
+	void *ret;
+
+	pthread_join((pthread_t)tid, &ret);
+	VERIFY3P(ret, ==, (void *)TS_MAGIC);
 }
 
 /*