stdlib: Undo post review change to 16adc58e73 [BZ #27749]

Post review removal of "goto restart" from
https://sourceware.org/pipermail/libc-alpha/2021-April/125470.html
introduced a bug when some atexit handers skipped.

Signed-off-by: Vitaly Buka <vitalybuka@google.com>

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

stdlib/Makefile

@@ -171,6 +171,7 @@ tests := \
   test-a64l \
   test-at_quick_exit-race \
   test-atexit-race \
+  test-atexit-recursive \
   test-bz22786 \
   test-canon \
   test-canon2 \

stdlib/exit.c

@@ -51,7 +51,10 @@ __run_exit_handlers (int status, struct exit_function_list **listp,
      exit (). */
   while (true)
     {
-      struct exit_function_list *cur = *listp;
+      struct exit_function_list *cur;
+
+    restart:
+      cur = *listp;
 
       if (cur == NULL)
 	{
@@ -113,7 +116,7 @@ __run_exit_handlers (int status, struct exit_function_list **listp,
 	  if (__glibc_unlikely (new_exitfn_called != __new_exitfn_called))
 	    /* The last exit function, or another thread, has registered
 	       more exit functions.  Start the loop over.  */
-            continue;
+	    goto restart;
 	}
 
       *listp = cur->next;

stdlib/test-atexit-recursive.c

@@ -0,0 +1,75 @@
+/* Support file for atexit/exit, etc. race tests (BZ #27749).
+   Copyright (C) 2023 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Check that atexit handler registed from another handler still called. */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/xunistd.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+static void
+atexit_cb (void)
+{
+}
+
+static void
+atexit_last (void)
+{
+  _exit (1);
+}
+
+static void
+atexit_recursive (void)
+{
+  atexit (&atexit_cb);
+  atexit (&atexit_last);
+}
+
+_Noreturn static void
+test_and_exit (int count)
+{
+  for (int i = 0; i < count; ++i)
+    atexit (&atexit_cb);
+  atexit (&atexit_recursive);
+  exit (0);
+}
+
+static int
+do_test (void)
+{
+  for (int i = 0; i < 100; ++i)
+    if (xfork () == 0)
+      test_and_exit (i);
+
+  for (int i = 0; i < 100; ++i)
+    {
+      int status;
+      xwaitpid (0, &status, 0);
+      if (!WIFEXITED (status))
+	FAIL_EXIT1 ("Failed iterations %d", i);
+      TEST_COMPARE (WEXITSTATUS (status), 1);
+    }
+
+  return 0;
+}
+
+#define TEST_FUNCTION do_test
+#include <support/test-driver.c>