emit thread id on linux / macOS

Author: kazuho

lib/picotls.c

@@ -7104,12 +7104,36 @@ int ptls_log_add_fd(int fd, float sample_ratio, const char *_points, const char
 
 void ptls_log__do_write_start(struct st_ptls_log_point_t *point, ptls_buffer_t *buf, void *smallbuf, size_t smallbufsize)
 {
+#if defined(__linux__) || defined(__APPLE__)
+    static PTLS_THREADLOCAL char tid[sizeof(",\"tid\":-9223372036854775808")];
+    static PTLS_THREADLOCAL int tid_ready;
+    if (!tid_ready) {
+        static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
+        pthread_mutex_lock(&mutex);
+        if (!tid_ready) {
+#if defined(__linux__)
+            sprintf(tid, ",\"tid\":%" PRId64, (int64_t)syscall(SYS_gettid));
+#elif defined(__APPLE__)
+            uint64_t t = 0;
+            (void)pthread_threadid_np(NULL, &t);
+            sprintf(tid, ",\"tid\":%" PRIu64, t);
+#else
+#error "unexpected platform"
+#endif
+            __sync_synchronize();
+            tid_ready = 1;
+        }
+        pthread_mutex_unlock(&mutex);
+    }
+#else
+    const char *tid = "";
+#endif
     const char *colon_at = strchr(point->name, ':');
 
     ptls_buffer_init(buf, smallbuf, smallbufsize);
 
-    int written = snprintf((char *)buf->base, buf->capacity, "{\"module\":\"%.*s\",\"type\":\"%s\"", (int)(colon_at - point->name),
-                           point->name, colon_at + 1);
+    int written = snprintf((char *)buf->base, buf->capacity, "{\"module\":\"%.*s\",\"type\":\"%s\"%s",
+                           (int)(colon_at - point->name), point->name, colon_at + 1, tid);
     assert(written > 0 && written < buf->capacity && "caller MUST provide smallbuf suffient to emit the prefix");
     buf->off = (size_t)written;
 }