src: set a default thread name for workers (#4664)

docs/src/threadpool.rst

@@ -17,6 +17,8 @@ is 1024).
 .. versionchanged:: 1.45.0 threads now have an 8 MB stack instead of the
    (sometimes too low) platform default.
 
+.. versionchanged:: 1.50.0 threads now have a default name of libuv-worker.
+
 The threadpool is global and shared across all event loops. When a particular
 function makes use of the threadpool (i.e. when using :c:func:`uv_queue_work`)
 libuv preallocates and initializes the maximum number of threads allowed by

src/threadpool.c

@@ -59,6 +59,7 @@ static void worker(void* arg) {
   struct uv__queue* q;
   int is_slow_work;
 
+  uv_thread_setname("libuv-worker");
   uv_sem_post((uv_sem_t*) arg);
   arg = NULL;
 

test/test-list.h

@@ -479,6 +479,7 @@ TEST_DECLARE   (thread_equal)
 TEST_DECLARE   (thread_affinity)
 TEST_DECLARE   (thread_priority)
 TEST_DECLARE   (thread_name)
+TEST_DECLARE   (thread_name_threadpool)
 TEST_DECLARE   (dlerror)
 #if (defined(__unix__) || (defined(__APPLE__) && defined(__MACH__))) && \
     !defined(__sun)
@@ -1197,6 +1198,7 @@ TASK_LIST_START
   TEST_ENTRY  (thread_affinity)
   TEST_ENTRY  (thread_priority)
   TEST_ENTRY  (thread_name)
+  TEST_ENTRY  (thread_name_threadpool)
   TEST_ENTRY  (dlerror)
   TEST_ENTRY  (ip4_addr)
   TEST_ENTRY  (ip6_addr_link_local)

test/test-thread-name.c

@@ -139,3 +139,51 @@ TEST_IMPL(thread_name) {
 
   return 0;
 }
+
+#define MAX_THREADS 4
+
+static void* executedThreads[MAX_THREADS] = { NULL };
+static int size;
+static uv_loop_t* loop;
+
+static unsigned short int key_exists(void* key) {
+  size_t i;
+  for (i = 0; i < MAX_THREADS; i++) {
+    if (executedThreads[i] == key) {
+      return 1;
+    }
+  }
+  return 0;
+}
+
+static void work_cb(uv_work_t* req) {
+  uv_thread_t thread = uv_thread_self();
+  req->data = &thread;
+  char tn[UV_PTHREAD_MAX_NAMELEN_NP];
+  ASSERT_OK(uv_thread_getname(&thread, tn, sizeof(tn)));
+  ASSERT_STR_EQ(tn, "libuv-worker");
+}
+
+static void after_work_cb(uv_work_t* req, int status) {
+  ASSERT_OK(status);
+  if (!key_exists(req->data)) {
+    executedThreads[size++] = req->data;
+  }
+
+  if (size == MAX_THREADS) {
+    return;
+  }
+
+  uv_queue_work(loop, req, work_cb, after_work_cb);
+}
+
+TEST_IMPL(thread_name_threadpool) {
+  uv_work_t req;
+  loop = uv_default_loop();
+  // Just to make sure all workers will be executed
+  // with the correct thread name
+  ASSERT_OK(uv_queue_work(loop, &req, work_cb, after_work_cb));
+  uv_run(loop, UV_RUN_DEFAULT);
+  MAKE_VALGRIND_HAPPY(uv_default_loop());
+  return 0;
+}