fixes #433 tasks can leak

While here I also improved the taskq.h comments (and removed a
stale prototype for nni_task_cancel), and addressed leaks in
the reqstress and multistress test programs.

4 files changed, 22 insertions, 4 deletions

diff --git a/src/core/taskq.c b/src/core/taskq.c
index a87e4729..d945e713 100644
--- a/src/core/taskq.c
+++ b/src/core/taskq.c
@@ -285,7 +285,7 @@ nni_task_fini(nni_task *task)
 {
 	NNI_ASSERT(!nni_list_node_active(&task->task_node));
 	nni_mtx_lock(&task->task_mtx);
-	if (task->task_run || task->task_exec) {
+	if ((task->task_run || task->task_exec) && (!task->task_done)) {
 		// destroy later.
 		task->task_fini = true;
 		nni_mtx_unlock(&task->task_mtx);
diff --git a/src/core/taskq.h b/src/core/taskq.h
index 513b15bb..918c6705 100644
--- a/src/core/taskq.h
+++ b/src/core/taskq.h
@@ -23,15 +23,29 @@ extern void nni_taskq_fini(nni_taskq *);
 // nni_task_dispatch sends the task to the queue.  It is guaranteed to
 // succeed.  (If the queue is shutdown, then the behavior is undefined.)
 extern void nni_task_dispatch(nni_task *);
+
+// nni_task_exec runs the task synchronously, if possible.  (Under certain
+// circumstances the task must be run asynchronously.)  The caller is
+// responsible for ensuring that it does not hold any resources which might
+// be acquired by the task itself; otherwise deadlock may occur.  (When in
+// doubt, use nni_task_dispatch instead.)
 extern void nni_task_exec(nni_task *);
+
+// nni_task_prep and nni_task_unprep are used by and exclusively for the aio
+// framework.  nni_task_prep marks the task as "scheduled" without actually
+// dispatching anything to it yet; nni_task_wait will block waiting for the
+// task to complete normally (after a call to nni_task_dispatch or
+// nni_task_exec), or for nni_task_unprep to be called.
 extern void nni_task_prep(nni_task *);
 extern void nni_task_unprep(nni_task *);
 
-// nni_task_cancel cancels the task.  It will wait for the task to complete
-// if it is already running.
-extern int  nni_task_cancel(nni_task *);
 extern void nni_task_wait(nni_task *);
 extern int  nni_task_init(nni_task **, nni_taskq *, nni_cb, void *);
+
+// nni_task_fini destroys the task.  It will reap resources asynchronously
+// if the task is currently executing.  Use nni_task_wait() first if the
+// callback must be stopped entirely before destroying the task (such as if
+// it reschedules the task.)
 extern void nni_task_fini(nni_task *);
 
 extern int  nni_taskq_sys_init(void);
diff --git a/tests/multistress.c b/tests/multistress.c
index 62838a73..1ec2bc6c 100644
--- a/tests/multistress.c
+++ b/tests/multistress.c
@@ -675,4 +675,6 @@ Main({
 			}
 		});
 	});
+
+	free(cases);
 })
diff --git a/tests/reqstress.c b/tests/reqstress.c
index f2ee502d..fa4b0975 100644
--- a/tests/reqstress.c
+++ b/tests/reqstress.c
@@ -290,4 +290,6 @@ Main({
 			}
 		});
 	});
+
+	free(cases);
 })