thread: add spdk_thread_is_idle()

This function add possibility to check if there are any scheduled operations
on particular thread.

Return from spdk_thread_poll() will be used as a way to load-balance and
signify if any work was performed during the single iteration.
A poller could return 0, but still be registered.

This helps especially in fio_plugin that only checked active_pollers or
messages via spdk_thread_poll().

Change-Id: Id6237278eb3b4bd4922b2abaa3c8ebd5e434d45d
Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-on: https://review.gerrithub.io/c/445915
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>

CHANGELOG.md

@@ -17,6 +17,9 @@ strip_size. The strip_size rpc param is deprecated.
 Added spdk_thread_has_pollers() function to verify if there are
 any registered pollers to be run on the thread.
 
+Added spdk_thread_is_idle() function to check if there are any scheduled operations
+to be performed on the thread at given time.
+
 ## v19.01:
 
 ### ocf bdev

examples/bdev/fio_plugin/fio_plugin.c

@@ -140,7 +140,9 @@ spdk_fio_cleanup_thread(struct spdk_fio_thread *fio_thread)
 {
 	spdk_thread_send_msg(fio_thread->thread, spdk_fio_bdev_close_targets, fio_thread);
 
-	while (spdk_fio_poll_thread(fio_thread) > 0) {}
+	while (!spdk_thread_is_idle(fio_thread->thread)) {
+		spdk_fio_poll_thread(fio_thread);
+	}
 
 	spdk_set_thread(fio_thread->thread);
 
@@ -330,9 +332,7 @@ spdk_init_thread_poll(void *arg)
 
 	do {
 		spdk_fio_poll_thread(fio_thread);
-	} while (!done);
-
-	while (spdk_fio_poll_thread(fio_thread) > 0) {};
+	} while (!done && !spdk_thread_is_idle(fio_thread->thread));
 
 	spdk_fio_cleanup_thread(fio_thread);
 

include/spdk/thread.h

@@ -277,6 +277,15 @@ int spdk_thread_has_active_pollers(struct spdk_thread *thread);
  */
 bool spdk_thread_has_pollers(struct spdk_thread *thread);
 
+/**
+ * Returns whether there are scheduled operations to be run on the thread.
+ *
+ * \param thread The thread to check.
+ *
+ * \return true if there are no scheduled operations, false otherwise.
+ */
+bool spdk_thread_is_idle(struct spdk_thread *thread);
+
 /**
  * Get count of allocated threads.
  */

lib/thread/thread.c

@@ -560,6 +560,17 @@ spdk_thread_has_pollers(struct spdk_thread *thread)
 	return true;
 }
 
+bool
+spdk_thread_is_idle(struct spdk_thread *thread)
+{
+	if (spdk_ring_count(thread->messages) ||
+	    spdk_thread_has_pollers(thread)) {
+		return false;
+	}
+
+	return true;
+}
+
 uint32_t
 spdk_thread_get_count(void)
 {