plugins/{airbrake,alarm_curl,alarm_xmpp}: fix race condition

A thread may run immediately after it's created. Trying to pass
parameter to thread using uwsgi_thread->data without preventing
the thread from accessing it first is a race condition. If the
thread accesses uwsgi_thread->data first, uwsgi gets killed by
SIGSEGV.

This patch creates a new function uwsgi_thread_new_with_data()
to assign user provided data to uwsgi_thread->data before the
thread is created.

core/utils.c

@@ -3752,7 +3752,7 @@ static void *uwsgi_thread_run(void *arg) {
 	return NULL;
 }
 
-struct uwsgi_thread *uwsgi_thread_new(void (*func) (struct uwsgi_thread *)) {
+struct uwsgi_thread *uwsgi_thread_new_with_data(void (*func) (struct uwsgi_thread *), void *data) {
 
 	struct uwsgi_thread *ut = uwsgi_calloc(sizeof(struct uwsgi_thread));
 
@@ -3769,6 +3769,7 @@ struct uwsgi_thread *uwsgi_thread_new(void (*func) (struct uwsgi_thread *)) {
 	uwsgi_socket_nb(ut->pipe[1]);
 
 	ut->func = func;
+	ut->data = data;
 
 	pthread_attr_init(&ut->tattr);
 	pthread_attr_setdetachstate(&ut->tattr, PTHREAD_CREATE_DETACHED);
@@ -3788,6 +3789,10 @@ error:
 	return NULL;
 }
 
+struct uwsgi_thread *uwsgi_thread_new(void (*func) (struct uwsgi_thread *)) {
+	return uwsgi_thread_new_with_data(func, NULL);
+}
+
 int uwsgi_kvlist_parse(char *src, size_t len, char list_separator, char kv_separator, ...) {
 	size_t i;
 	va_list ap;

plugins/airbrake/airbrake_plugin.c

@@ -271,12 +271,11 @@ static void uwsgi_airbrake_loop(struct uwsgi_thread *ut) {
 }
 
 static void uwsgi_airbrake_init(struct uwsgi_alarm_instance *uai) {
-	struct uwsgi_thread *ut = uwsgi_thread_new(uwsgi_airbrake_loop);
-	if (!ut) return;
-	uai->data_ptr = ut;
 	struct uwsgi_airbrake_config *uacc = uwsgi_calloc(sizeof(struct uwsgi_airbrake_config));
 	uacc->arg = uai->arg;
-	ut->data = uacc;
+	struct uwsgi_thread *ut = uwsgi_thread_new_with_data(uwsgi_airbrake_loop, uacc);
+	if (!ut) return;
+	uai->data_ptr = ut;
 }
 
 static void uwsgi_airbrake_func(struct uwsgi_alarm_instance *uai, char *msg, size_t len) {

plugins/alarm_curl/alarm_curl_plugin.c

@@ -234,12 +234,11 @@ static void uwsgi_alarm_curl_loop(struct uwsgi_thread *ut) {
 }
 
 static void uwsgi_alarm_curl_init(struct uwsgi_alarm_instance *uai) {
-	struct uwsgi_thread *ut = uwsgi_thread_new(uwsgi_alarm_curl_loop);
-	if (!ut) return;
-	uai->data_ptr = ut;
 	struct uwsgi_alarm_curl_config *uacc = uwsgi_calloc(sizeof(struct uwsgi_alarm_curl_config));
 	uacc->arg = uai->arg;
-	ut->data = uacc;
+	struct uwsgi_thread *ut = uwsgi_thread_new_with_data(uwsgi_alarm_curl_loop, uacc);
+	if (!ut) return;
+	uai->data_ptr = ut;
 }
 
 // pipe the message into the thread;

plugins/alarm_xmpp/alarm_xmpp_plugin.c

@@ -4,10 +4,9 @@ void uwsgi_alarm_xmpp_loop(struct uwsgi_thread *);
 
 static void uwsgi_alarm_xmpp_init(struct uwsgi_alarm_instance *uai) {
 
-	struct uwsgi_thread *ut = uwsgi_thread_new(uwsgi_alarm_xmpp_loop);
+	struct uwsgi_thread *ut = uwsgi_thread_new_with_data(uwsgi_alarm_xmpp_loop, uai->arg);
 	if (!ut) return;
 	uai->data_ptr = ut;
-	ut->data = uai->arg;
 }
 
 // pipe the message into the thread;

uwsgi.h

@@ -4175,6 +4175,7 @@ struct uwsgi_thread {
 	void (*func) (struct uwsgi_thread *);
 };
 struct uwsgi_thread *uwsgi_thread_new(void (*)(struct uwsgi_thread *));
+struct uwsgi_thread *uwsgi_thread_new_with_data(void (*)(struct uwsgi_thread *), void *data);
 
 struct uwsgi_offload_request {
 	// the request socket