diff --git a/stdlib/Makefile b/stdlib/Makefile
index 8b0ac63ddb3..7eec68b73a2 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -273,6 +273,7 @@ tests := \
tst-bsearch \
tst-bz20544 \
tst-canon-bz26341 \
+ tst-concurrent-exit \
tst-cxa_atexit \
tst-environ \
tst-getrandom \
diff --git a/stdlib/exit.c b/stdlib/exit.c
index 5166c780443..bbaf1388068 100644
--- a/stdlib/exit.c
+++ b/stdlib/exit.c
@@ -132,9 +132,17 @@ __run_exit_handlers (int status, struct exit_function_list **listp,
}
+/* The lock handles concurrent exit(), even though the C/POSIX standard states
+ that calling exit() more than once is UB. The recursive lock allows
+ atexit() handlers or destructors to call exit() itself. In this case, the
+ handler list execution will resume at the point of the current handler. */
+__libc_lock_define_initialized_recursive (static, __exit_lock)
+
void
exit (int status)
{
+ /* The exit should never return, so there is no need to unlock it. */
+ __libc_lock_lock_recursive (__exit_lock);
__run_exit_handlers (status, &__exit_funcs, true, true);
}
libc_hidden_def (exit)
diff --git a/stdlib/tst-concurrent-exit.c b/stdlib/tst-concurrent-exit.c
new file mode 100644
index 00000000000..1141130f87f
--- /dev/null
+++ b/stdlib/tst-concurrent-exit.c
@@ -0,0 +1,157 @@
+/* Check if exit can be called concurrently by multiple threads.
+ Copyright (C) 2024 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
+ . */
+
+#include
+#include
+#include
+#include
+#include
+#include
+#include
+
+#define MAX_atexit 32
+
+static pthread_barrier_t barrier;
+
+static void *
+tf (void *closure)
+{
+ xpthread_barrier_wait (&barrier);
+ exit (0);
+
+ return NULL;
+}
+
+static const char expected[] = "00000000000000000000000003021121130211";
+static char crumbs[sizeof (expected)];
+static int next_slot = 0;
+
+static void
+exit_with_flush (int code)
+{
+ fflush (stdout);
+ /* glibc allows recursive exit, the atexit handlers execution will be
+ resumed from the where the previous exit was interrupted. */
+ exit (code);
+}
+
+/* Take some time, so another thread potentially issue exit. */
+#define SETUP_NANOSLEEP \
+ if (nanosleep (&(struct timespec) { .tv_sec = 0, .tv_nsec = 1000L }, \
+ NULL) != 0) \
+ FAIL_EXIT1 ("nanosleep: %m")
+
+static void
+fn0 (void)
+{
+ crumbs[next_slot++] = '0';
+ SETUP_NANOSLEEP;
+}
+
+static void
+fn1 (void)
+{
+ crumbs[next_slot++] = '1';
+ SETUP_NANOSLEEP;
+}
+
+static void
+fn2 (void)
+{
+ crumbs[next_slot++] = '2';
+ atexit (fn1);
+ SETUP_NANOSLEEP;
+}
+
+static void
+fn3 (void)
+{
+ crumbs[next_slot++] = '3';
+ atexit (fn2);
+ atexit (fn0);
+ SETUP_NANOSLEEP;
+}
+
+static void
+fn_final (void)
+{
+ TEST_COMPARE_STRING (crumbs, expected);
+ exit_with_flush (0);
+}
+
+_Noreturn static void
+child (void)
+{
+ enum { nthreads = 8 };
+
+ xpthread_barrier_init (&barrier, NULL, nthreads + 1);
+
+ pthread_t thr[nthreads];
+ for (int i = 0; i < nthreads; i++)
+ thr[i] = xpthread_create (NULL, tf, NULL);
+
+ xpthread_barrier_wait (&barrier);
+
+ for (int i = 0; i < nthreads; i++)
+ {
+ pthread_join (thr[i], NULL);
+ /* It should not be reached, it means that thread did not exit for
+ some reason. */
+ support_record_failure ();
+ }
+
+ exit (2);
+}
+
+static int
+do_test (void)
+{
+ /* Register a large number of handler that will trigger a heap allocation
+ for the handle state. On exit, each block will be freed after the
+ handle is processed. */
+ int slots_remaining = MAX_atexit;
+
+ /* Register this first so it can verify expected order of the rest. */
+ atexit (fn_final); --slots_remaining;
+
+ TEST_VERIFY_EXIT (atexit (fn1) == 0); --slots_remaining;
+ TEST_VERIFY_EXIT (atexit (fn3) == 0); --slots_remaining;
+ TEST_VERIFY_EXIT (atexit (fn1) == 0); --slots_remaining;
+ TEST_VERIFY_EXIT (atexit (fn2) == 0); --slots_remaining;
+ TEST_VERIFY_EXIT (atexit (fn1) == 0); --slots_remaining;
+ TEST_VERIFY_EXIT (atexit (fn3) == 0); --slots_remaining;
+
+ while (slots_remaining > 0)
+ {
+ TEST_VERIFY_EXIT (atexit (fn0) == 0); --slots_remaining;
+ }
+
+ pid_t pid = xfork ();
+ if (pid != 0)
+ {
+ int status;
+ xwaitpid (pid, &status, 0);
+ TEST_VERIFY (WIFEXITED (status));
+ }
+ else
+ child ();
+
+ return 0;
+}
+
+#include