thread: add spdk_thread_is_running()

This function can be useful to query if a thread
had spdk_thread_exit() called on it yet.  Internally
we have both EXITING and EXITED state - so
!spdk_thread_is_running() can be used to detect a
thread that is in either of those states.

Signed-off-by: Jim Harris <james.r.harris@intel.com>
Change-Id: I2f6fb024a6b1bc895fdc5132c722abc10f5d30f9
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/15512
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>
Reviewed-by: Aleksey Marchuk <alexeymar@nvidia.com>

CHANGELOG.md

@@ -70,6 +70,9 @@ for writing and decoding of the the double data type.
 Added `spdk_thread_get_app_thread` which returns the first thread that was created using
 `spdk_thread_create`.
 
+Added `spdk_thread_is_running`.  This returns `true` for a running thread, or `false` if
+its exit process has started using `spdk_thread_exit`.
+
 ## v22.09
 
 ### accel

include/spdk/thread.h

@@ -285,12 +285,28 @@ int spdk_thread_exit(struct spdk_thread *thread);
 /**
  * Returns whether the thread is marked as exited.
  *
+ * A thread is exited only after it has spdk_thread_exit() called on it, and
+ * it has been polled until any outstanding operations targeting this
+ * thread have completed.  This may include poller unregistrations, io channel
+ * unregistrations, or outstanding spdk_thread_send_msg calls.
+ *
  * \param thread The thread to query.
  *
  * \return true if marked as exited, false otherwise.
  */
 bool spdk_thread_is_exited(struct spdk_thread *thread);
 
+/**
+ * Returns whether the thread is still running.
+ *
+ * A thread is considered running until it has * spdk_thread_exit() called on it.
+ *
+ * \param thread The thread to query.
+ *
+ * \return true if still running, false otherwise.
+ */
+bool spdk_thread_is_running(struct spdk_thread *thread);
+
 /**
  * Destroy a thread, releasing all of its resources. May only be called
  * on a thread previously marked as exited.

lib/thread/spdk_thread.map

@@ -9,6 +9,7 @@
 	spdk_thread_get_app_thread;
 	spdk_set_thread;
 	spdk_thread_exit;
+	spdk_thread_is_running;
 	spdk_thread_is_exited;
 	spdk_thread_destroy;
 	spdk_thread_get_ctx;

lib/thread/thread.c

@@ -594,6 +594,12 @@ spdk_thread_exit(struct spdk_thread *thread)
 	return 0;
 }
 
+bool
+spdk_thread_is_running(struct spdk_thread *thread)
+{
+	return thread->state == SPDK_THREAD_STATE_RUNNING;
+}
+
 bool
 spdk_thread_is_exited(struct spdk_thread *thread)
 {