Index: kern_task.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_task.c,v
retrieving revision 1.27
diff -u -p -r1.27 kern_task.c
--- kern_task.c	19 Dec 2019 17:40:11 -0000	1.27
+++ kern_task.c	4 Jun 2020 23:40:13 -0000
@@ -36,6 +36,14 @@ static struct lock_type taskq_lock_type 
 
 #endif /* WITNESS */
 
+struct taskq_thread {
+	SLIST_ENTRY(taskq_thread)
+				 tt_entry;
+	struct proc		*tt_thread;
+};
+
+SLIST_HEAD(taskq_threads, taskq_thread);
+
 struct taskq {
 	enum {
 		TQ_S_CREATED,
@@ -49,6 +57,7 @@ struct taskq {
 	const char		*tq_name;
 
 	struct mutex		 tq_mtx;
+	struct taskq_threads	 tq_threads;
 	struct task_list	 tq_worklist;
 #ifdef WITNESS
 	struct lock_object	 tq_lock_object;
@@ -65,6 +74,7 @@ struct taskq taskq_sys = {
 	0,
 	taskq_sys_name,
 	MUTEX_INITIALIZER(IPL_HIGH),
+	SLIST_HEAD_INITIALIZER(taskq_sys.tq_threads),
 	TAILQ_HEAD_INITIALIZER(taskq_sys.tq_worklist),
 #ifdef WITNESS
 	{
@@ -84,6 +94,7 @@ struct taskq taskq_sys_mp = {
 	TASKQ_MPSAFE,
 	taskq_sys_mp_name,
 	MUTEX_INITIALIZER(IPL_HIGH),
+	SLIST_HEAD_INITIALIZER(taskq_sys_mp.tq_threads),
 	TAILQ_HEAD_INITIALIZER(taskq_sys_mp.tq_worklist),
 #ifdef WITNESS
 	{
@@ -131,6 +152,7 @@ taskq_create(const char *name, unsigned 
 	tq->tq_flags = flags;
 
 	mtx_init_flags(&tq->tq_mtx, ipl, name, 0);
+	SLIST_INIT(&tq->tq_threads);
 	TAILQ_INIT(&tq->tq_worklist);
 
 #ifdef WITNESS
@@ -220,13 +242,22 @@ taskq_create_thread(void *arg)
 	mtx_leave(&tq->tq_mtx);
 }
 
-void
-taskq_barrier(struct taskq *tq)
+static void
+taskq_do_barrier(struct taskq *tq)
 {
 	struct cond c = COND_INITIALIZER();
 	struct task t = TASK_INITIALIZER(taskq_barrier_task, &c);
+	struct proc *thread = curproc;
+	struct taskq_thread *tt;
 
-	WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
+	mtx_enter(&tq->tq_mtx);
+	SLIST_FOREACH(tt, &tq->tq_threads, tt_entry) {
+		if (tt->tt_thread == thread)
+			break;
+	}
+	mtx_leave(&tq->tq_mtx);
+	if (tt != NULL)
+		return;
 
 	SET(t.t_flags, TASK_BARRIER);
 	task_add(tq, &t);
@@ -234,19 +265,22 @@ taskq_barrier(struct taskq *tq)
 }
 
 void
-taskq_del_barrier(struct taskq *tq, struct task *del)
+taskq_barrier(struct taskq *tq)
 {
-	struct cond c = COND_INITIALIZER();
-	struct task t = TASK_INITIALIZER(taskq_barrier_task, &c);
+	WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
+
+	taskq_do_barrier(tq);
+}
 
+void
+taskq_del_barrier(struct taskq *tq, struct task *t)
+{
 	WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
 
-	if (task_del(tq, del))
+	if (task_del(tq, t))
 		return;
 
-	SET(t.t_flags, TASK_BARRIER);
-	task_add(tq, &t);
-	cond_wait(&c, "tqbar");
+	taskq_do_barrier(tq);
 }
 
 void
@@ -354,6 +388,7 @@ retry:
 void
 taskq_thread(void *xtq)
 {
+	struct taskq_thread self = { .tt_thread = curproc };
 	struct taskq *tq = xtq;
 	struct task work;
 	int last;
@@ -361,6 +396,10 @@ taskq_thread(void *xtq)
 	if (ISSET(tq->tq_flags, TASKQ_MPSAFE))
 		KERNEL_UNLOCK();
 
+	mtx_enter(&tq->tq_mtx);
+	SLIST_INSERT_HEAD(&tq->tq_threads, &self, tt_entry);
+	mtx_leave(&tq->tq_mtx);
+
 	WITNESS_CHECKORDER(&tq->tq_lock_object, LOP_NEWORDER, NULL);
 
 	while (taskq_next_work(tq, &work)) {
@@ -371,6 +410,7 @@ taskq_thread(void *xtq)
 	}
 
 	mtx_enter(&tq->tq_mtx);
+	SLIST_REMOVE(&tq->tq_threads, &self, taskq_thread, tt_entry);
 	last = (--tq->tq_running == 0);
 	mtx_leave(&tq->tq_mtx);