Fix pthread_setname_np race condition in thread_base::event_loop

The thread->m_thread member is set via pthread_create(3). However,
it is not guaranteed that pthread_create writes this member before
it returns. Since thread_base::event_loop is the function executed
by pthread_create, we cannot assume that it is set. Instead, use
pthread_self() which is guaranteed to be set.

src/torrent/utils/thread_base.cc

@@ -92,7 +92,8 @@ thread_base::event_loop(thread_base* thread) {
 #if defined(HAS_PTHREAD_SETNAME_NP_DARWIN)
   pthread_setname_np(thread->name());
 #elif defined(HAS_PTHREAD_SETNAME_NP_GENERIC)
-  pthread_setname_np(thread->m_thread, thread->name());
+  // Cannot use thread->m_thread here as it may not be set before pthread_create returns.
+  pthread_setname_np(pthread_self(), thread->name());
 #endif
 
   lt_log_print(torrent::LOG_THREAD_NOTICE, "%s: Starting thread.", thread->name());