taskq: add taskq_try_dispatch_ent()

Non-blocking form of taskq_dispatch_ent(), returns false if it can't
acquire the taskq lock.

Signed-off-by: Rob Norris <rob.norris@klarasystems.com>

include/os/freebsd/spl/sys/taskq.h

@@ -91,6 +91,8 @@ extern taskqid_t taskq_dispatch_delay(taskq_t *, task_func_t, void *,
     uint_t, clock_t);
 extern void taskq_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
     taskq_ent_t *);
+extern boolean_t taskq_try_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
+    taskq_ent_t *);
 extern int taskq_empty_ent(taskq_ent_t *);
 taskq_t	*taskq_create(const char *, int, pri_t, int, int, uint_t);
 taskq_t	*taskq_create_instance(const char *, int, int, pri_t, int, int, uint_t);

include/os/linux/spl/sys/taskq.h

@@ -146,6 +146,8 @@ extern taskqid_t taskq_dispatch_delay(taskq_t *, task_func_t, void *,
     uint_t, clock_t);
 extern void taskq_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
     taskq_ent_t *);
+extern boolean_t taskq_try_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
+    taskq_ent_t *);
 extern int taskq_empty_ent(taskq_ent_t *);
 extern void taskq_init_ent(taskq_ent_t *);
 extern taskq_t *taskq_create(const char *, int, pri_t, int, int, uint_t);

include/sys/zfs_context.h

@@ -503,6 +503,8 @@ extern taskqid_t taskq_dispatch_delay(taskq_t *, task_func_t, void *, uint_t,
     clock_t);
 extern void	taskq_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
     taskq_ent_t *);
+extern boolean_t taskq_try_dispatch_ent(taskq_t *, task_func_t, void *, uint_t,
+    taskq_ent_t *);
 extern int	taskq_empty_ent(taskq_ent_t *);
 extern void	taskq_init_ent(taskq_ent_t *);
 extern void	taskq_destroy(taskq_t *);

lib/libzpool/taskq.c

@@ -156,8 +156,8 @@ taskq_init_ent(taskq_ent_t *t)
 	t->tqent_flags = 0;
 }
 
-void
+static void
-taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+taskq_dispatch_ent_impl(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
     taskq_ent_t *t)
 {
 	ASSERT(func != NULL);
@@ -170,7 +170,6 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 	/*
 	 * Enqueue the task to the underlying queue.
 	 */
-	mutex_enter(&tq->tq_lock);
 
 	if (flags & TQ_FRONT) {
 		t->tqent_next = tq->tq_task.tqent_next;
@@ -184,9 +183,28 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 	t->tqent_func = func;
 	t->tqent_arg = arg;
 	cv_signal(&tq->tq_dispatch_cv);
+}
+
+void
+taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+    taskq_ent_t *t)
+{
+	mutex_enter(&tq->tq_lock);
+	taskq_dispatch_ent_impl(tq, func, arg, flags, t);
 	mutex_exit(&tq->tq_lock);
 }
 
+boolean_t
+taskq_try_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+    taskq_ent_t *t)
+{
+	if (!mutex_tryenter(&tq->tq_lock))
+		return (B_FALSE);
+	taskq_dispatch_ent_impl(tq, func, arg, flags, t);
+	mutex_exit(&tq->tq_lock);
+	return (B_TRUE);
+}
+
 void
 taskq_wait(taskq_t *tq)
 {

module/os/freebsd/spl/spl_taskq.c

@@ -411,6 +411,15 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint32_t flags,
 	taskqueue_enqueue(tq->tq_queue, &task->tqent_task);
 }
 
+boolean_t
+taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint32_t flags,
+    taskq_ent_t *task)
+{
+	/* XXX: implement me -- robn, 2023-10-23 */
+	taskq_dispatch_ent(tq, func, arg, flags, task);
+	return (B_TRUE);
+}
+
 void
 taskq_wait(taskq_t *tq)
 {

module/os/linux/spl/spl-taskq.c

@@ -673,17 +673,13 @@ out:
 }
 EXPORT_SYMBOL(taskq_dispatch_delay);
 
-void
+static void
-taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+taskq_dispatch_ent_impl(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
     taskq_ent_t *t)
 {
-	unsigned long irqflags;
 	ASSERT(tq);
 	ASSERT(func);
 
-	spin_lock_irqsave_nested(&tq->tq_lock, irqflags,
-	    tq->tq_lock_class);
-
 	/* Taskq being destroyed and all tasks drained */
 	if (!(tq->tq_flags & TASKQ_ACTIVE)) {
 		t->tqent_id = TASKQID_INVALID;
@@ -694,7 +690,7 @@ taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
 		/* Dynamic taskq may be able to spawn another thread */
 		if (!(tq->tq_flags & TASKQ_DYNAMIC) ||
 		    taskq_thread_spawn(tq) == 0)
-			goto out2;
+			return;
 		flags |= TQ_FRONT;
 	}
 
@@ -734,11 +730,45 @@ out:
 	/* Spawn additional taskq threads if required. */
 	if (tq->tq_nactive == tq->tq_nthreads)
 		(void) taskq_thread_spawn(tq);
-out2:
+}
+
+void
+taskq_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+    taskq_ent_t *t)
+{
+	unsigned long irqflags;
+
+	spin_lock_irqsave_nested(&tq->tq_lock, irqflags,
+	    tq->tq_lock_class);
+
+	taskq_dispatch_ent_impl(tq, func, arg, flags, t);
+
 	spin_unlock_irqrestore(&tq->tq_lock, irqflags);
 }
 EXPORT_SYMBOL(taskq_dispatch_ent);
 
+boolean_t
+taskq_try_dispatch_ent(taskq_t *tq, task_func_t func, void *arg, uint_t flags,
+    taskq_ent_t *t)
+{
+	unsigned long irqflags;
+
+	/*
+	 * XXX I don't _think_ losing _nested matters, because I think its
+	 *     only related to lockdep, and we don't have access to that anyway
+	 *       -- robn, 2023-10-23
+	 */
+	if (!spin_trylock_irqsave(&tq->tq_lock, irqflags))
+		return (B_FALSE);
+
+	taskq_dispatch_ent_impl(tq, func, arg, flags, t);
+
+	spin_unlock_irqrestore(&tq->tq_lock, irqflags);
+
+	return (B_TRUE);
+}
+EXPORT_SYMBOL(taskq_try_dispatch_ent);
+
 int
 taskq_empty_ent(taskq_ent_t *t)
 {