Don't close epoll FD if it's already closed

src/cc/BPFTable.cc

@@ -136,12 +136,14 @@ StatusTuple BPFPerfBuffer::close_all_cpu() {
   std::string errors;
   bool has_error = false;
 
-  int close_res = close(epfd_);
-  epfd_ = -1;
-  ep_events_.reset();
-  if (close_res != 0) {
-    has_error = true;
-    errors += std::string(std::strerror(errno)) + "\n";
+  if (epfd_ >= 0) {
+    int close_res = close(epfd_);
+    epfd_ = -1;
+    ep_events_.reset();
+    if (close_res != 0) {
+      has_error = true;
+      errors += std::string(std::strerror(errno)) + "\n";
+    }
   }
 
   std::vector<int> opened_cpus;

src/cc/perf_reader.c

@@ -244,7 +244,7 @@ void perf_reader_event_read(struct perf_reader *reader) {
       if (reader->lost_cb) {
         reader->lost_cb(lost);
       } else {
-        fprintf(stderr, "Possibly lost " PRIu64 " samples\n", lost);
+        fprintf(stderr, "Possibly lost %" PRIu64 " samples\n", lost);
       }
     } else if (e->type == PERF_RECORD_SAMPLE) {
       if (reader->type == PERF_TYPE_TRACEPOINT)