qcacld-3.0: Fix race condition between external threads and module stop

External threads and interface change timer are racing against each other
leading to various side effects. Fix the race condition between external
threads and interface change timer by leveraging existing ssr/driver
unload protection mechanism for module stop.

Change-Id: Ic3d6d516161afee1dd65abb8f1eafe160bea54ff
CRs-Fixed: 2021483

core/cds/inc/cds_sched.h

@@ -467,6 +467,13 @@ void cds_ssr_unprotect(const char *caller_func);
 bool cds_wait_for_external_threads_completion(const char *caller_func);
 int cds_get_gfp_flags(void);
 
+/**
+ * cds_return_external_threads_count() - return active external thread calls
+ *
+ * Return: total number of active extrenal threads in driver
+ */
+int cds_return_external_threads_count(void);
+
 /**
  * cds_shutdown_notifier_register() - Register for shutdown notification
  * @cb          : Call back to be called

core/cds/src/cds_sched.c

@@ -1179,6 +1179,11 @@ bool cds_wait_for_external_threads_completion(const char *caller_func)
 	return true;
 }
 
+int cds_return_external_threads_count(void)
+{
+	return  atomic_read(&ssr_protect_entry_count);
+}
+
 /**
  * cds_get_gfp_flags(): get GFP flags
  *

core/hdd/src/wlan_hdd_main.c

@@ -8735,6 +8735,16 @@ int hdd_wlan_stop_modules(hdd_context_t *hdd_ctx)
 	mutex_lock(&hdd_ctx->iface_change_lock);
 	hdd_ctx->stop_modules_in_progress = true;
 
+	if (cds_return_external_threads_count() || hdd_ctx->isWiphySuspended) {
+		mutex_unlock(&hdd_ctx->iface_change_lock);
+		hdd_warn("External threads %d wiphy suspend %d",
+			cds_return_external_threads_count(),
+			hdd_ctx->isWiphySuspended);
+		qdf_mc_timer_start(&hdd_ctx->iface_change_timer,
+				   hdd_ctx->config->iface_change_wait_time);
+		return 0;
+	}
+
 	hdd_info("Present Driver Status: %d", hdd_ctx->driver_status);
 
 	switch (hdd_ctx->driver_status) {