DAOS-18888 client: validation check when event completion

src/client/api/client_internal.h

@@ -1,5 +1,6 @@
 /**
  * (C) Copyright 2016-2022 Intel Corporation.
+ * (C) Copyright 2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -44,6 +45,9 @@ struct daos_event_callback {
 	d_list_t		evx_comp_list;
 };
 
+#define DAOS_EVENT_GEN_BITS (30)
+#define DAOS_EVENT_GEN_MAX  ((1 << DAOS_EVENT_GEN_BITS) - 1)
+
 struct daos_event_private {
 	daos_handle_t		evx_eqh;
 	d_list_t		evx_link;
@@ -52,10 +56,9 @@ struct daos_event_private {
 	unsigned int		evx_nchild;
 	unsigned int		evx_nchild_running;
 	unsigned int		evx_nchild_comp;
-	/** flag to indicate whether event is a barrier event */
-	unsigned int		is_barrier:1;
-	/** flag to indicate whether to convert DER to errno */
-	unsigned int		is_errno:1;
+
+	unsigned int evx_gen : DAOS_EVENT_GEN_BITS, /* Generation for validation when completion. */
+	    is_barrier : 1, /* Barrier event. */ is_errno : 1; /* Whether convert DER to errno. */
 
 	unsigned int		evx_flags;
 	ATOMIC daos_ev_status_t	evx_status;

src/client/api/event.c

@@ -521,6 +521,22 @@ daos_event_complete(struct daos_event *ev, int rc)
 	}
 }
 
+void
+daos_event_complete_with_check(struct daos_event *ev, int rc, void *data)
+{
+	struct daos_event_private *evx = daos_ev2evx(ev);
+	unsigned int               gen;
+
+	D_ASSERT(data != NULL);
+
+	gen = *(unsigned int *)data;
+
+	if (unlikely(evx->evx_gen != gen))
+		D_WARN("Skip completion against stale event %p: %u vs %u\n", ev, evx->evx_gen, gen);
+	else
+		daos_event_complete(ev, rc);
+}
+
 struct ev_progress_arg {
 	struct daos_eq_private		*eqx;
 	struct daos_event_private	*evx;
@@ -1004,6 +1020,19 @@ daos_event_destroy_children(struct daos_event *ev, bool force)
 	return rc;
 }
 
+unsigned int
+daos_event_bump_gen(daos_event_t *ev)
+{
+	struct daos_event_private *evx = daos_ev2evx(ev);
+
+	if (likely(evx->evx_gen < DAOS_EVENT_GEN_MAX))
+		evx->evx_gen++;
+	else
+		evx->evx_gen = 1;
+
+	return evx->evx_gen;
+}
+
 /**
  * Add the event to the event queue, and if there is parent, add
  * it to its child list as well.

src/client/api/task.c

@@ -1,5 +1,6 @@
 /**
  * (C) Copyright 2017-2021 Intel Corporation.
+ * (C) Copyright 2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -35,8 +36,16 @@ task_is_valid(tse_task_t *task)
 static int
 task_comp_event(tse_task_t *task, void *data)
 {
+	daos_event_t *ev;
+
 	D_ASSERT(task_is_valid(task));
-	daos_event_complete(task_ptr2args(task)->ta_ev, task->dt_result);
+
+	ev = task_ptr2args(task)->ta_ev;
+	if (daos_event_is_priv(ev))
+		daos_event_complete_with_check(ev, task->dt_result, data);
+	else
+		daos_event_complete(ev, task->dt_result);
+
 	return 0;
 }
 
@@ -53,6 +62,8 @@ dc_task_create(tse_task_func_t func, tse_sched_t *sched, daos_event_t *ev,
 {
 	struct daos_task_args *args;
 	tse_task_t	      *task;
+	unsigned int           gen;
+	size_t                 size = 0;
 	int		       rc;
 
 	if (sched == NULL) {
@@ -71,8 +82,13 @@ dc_task_create(tse_task_func_t func, tse_sched_t *sched, daos_event_t *ev,
 	args = task_ptr2args(task);
 	args->ta_magic = DAOS_TASK_MAGIC;
 	if (ev) {
+		if (daos_event_is_priv(ev)) {
+			gen  = daos_event_bump_gen(ev);
+			size = sizeof(gen);
+		}
+
 		/** register a comp cb on the task to complete the event */
-		rc = tse_task_register_comp_cb(task, task_comp_event, NULL, 0);
+		rc = tse_task_register_comp_cb(task, task_comp_event, size ? &gen : NULL, size);
 		if (rc != 0)
 			D_GOTO(failed, rc);
 		args->ta_ev = ev;

src/include/daos/event.h

@@ -1,5 +1,6 @@
 /**
  * (C) Copyright 2015-2024 Intel Corporation.
+ * (C) Copyright 2026 Hewlett Packard Enterprise Development LP
  *
  * SPDX-License-Identifier: BSD-2-Clause-Patent
  */
@@ -83,6 +84,16 @@ int daos_event_init_adv(struct daos_event *ev, enum daos_ev_flags flags,
 void
 daos_event_complete(daos_event_t *ev, int rc);
 
+/**
+ * Mark the event completed with validation check firstly.
+ *
+ * \param ev   [IN]	event to complete.
+ * \param rc   [IN]	operation return code.
+ * \param data [IN]	argument for completion callback verification.
+ */
+void
+daos_event_complete_with_check(daos_event_t *ev, int rc, void *data);
+
 /**
  * Mark the event launched, i.e. move this event to running list.
  *
@@ -120,6 +131,8 @@ daos_event_destroy(struct daos_event *ev, bool force);
 int
 daos_event_destroy_children(struct daos_event *ev, bool force);
 
+unsigned int
+daos_event_bump_gen(daos_event_t *ev);
 
 /**
  * Wait for completion of the private event