Test case for bug 30619

sysdeps/pthread/Makefile

@@ -335,6 +335,7 @@ tests += \
   tst-atfork3 \
   tst-atfork4 \
   tst-create1 \
+  tst-thread-dlopen-fork \
   tst-fini1 \
   tst-pt-tls4 \
   # tests
@@ -351,6 +352,7 @@ modules-names += \
   tst-atfork3mod \
   tst-atfork4mod \
   tst-create1mod \
+  tst-thread-dlopen-fork-mod \
   tst-fini1mod \
   tst-tls4moda \
   tst-tls4modb \
@@ -525,4 +527,11 @@ LDFLAGS-tst-create1 = -Wl,-export-dynamic
 $(objpfx)tst-create1: $(shared-thread-library)
 $(objpfx)tst-create1.out: $(objpfx)tst-create1mod.so
 
+# Create multiple shared objects to be used by the test.
+tst-thread-dlopen-fork.sos := \
+  $(patsubst %,$(objpfx)tst-thread-dlopen-fork-mod-%.so,$(shell seq 0 16))
+$(tst-thread-dlopen-fork.sos): $(objpfx)tst-thread-dlopen-fork-mod.so
+	cp -f $< $@
+$(objpfx)tst-thread-dlopen-fork.out: $(tst-thread-dlopen-fork.sos)
+
 endif

sysdeps/pthread/tst-thread-dlopen-fork-mod.c

@@ -0,0 +1 @@
+/* Empty shared object.  */

sysdeps/pthread/tst-thread-dlopen-fork.c

@@ -0,0 +1,133 @@
+/* Test that dlopen works after concurrent fork.
+   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/>.  */
+
+#include <array_length.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xthread.h>
+#include <support/xunistd.h>
+#include <unistd.h>
+
+/* Use atomics to make sure that issues with dlopen/fork come from
+   implementation problems, and not from exposing the handle of a
+   partially initialized link map after dlopen returned.  */
+static void *_Atomic handles[17];
+
+/* Set to true if the dlopen thread has exited.  */
+static _Atomic bool requested_exit;
+
+/* Used to start the forking and the dlopen thread at the same time.  */
+static pthread_barrier_t barrier;
+
+/* Returns the file to open for IDX.  */
+static char *
+dso_name (int idx)
+{
+  return xasprintf ("tst-thread-dlopen-fork-mod-%d.so", idx);
+}
+
+static void *
+forking_thread (void *closure)
+{
+  xpthread_barrier_wait (&barrier);
+  int mode = 0;
+  while (!requested_exit)
+    {
+      pid_t pid = xfork ();
+      if (pid == 0)
+        {
+          switch (mode)
+            {
+            case 0:
+              /* Try to open all handles.  */
+              for (int i = 0; i < array_length (handles); ++i)
+                {
+                  char *name = dso_name (i);
+                  void *handle = xdlopen (name, RTLD_LAZY);
+                  if (handles[i] != NULL)
+                    TEST_VERIFY (handle == handles[i]);
+                  free (name);
+                }
+              mode = 1;
+              break;
+            case 1:
+              /* Try to open all unopened handles.  */
+              for (int i = 0; i < array_length (handles); ++i)
+                if (handles[i] == NULL)
+                  {
+                    char *name = dso_name (i);
+                    xdlopen (name, RTLD_LAZY);
+                    free (name);
+                  }
+              mode = 2;
+              break;
+            case 2:
+              /* Try to close all opened handles.  */
+              for (int i = 0; i < array_length (handles); ++i)
+                if (handles[i] != NULL)
+                  xdlclose (handles[i]);
+              break;
+            }
+          _exit (0);
+        }
+      int status;
+      xwaitpid (pid, &status, 0);
+      TEST_COMPARE (status, 0);
+    }
+  return NULL;
+}
+
+static void *
+dlopen_thread (void *closure)
+{
+  xpthread_barrier_wait (&barrier);
+  srand (1);
+  for (int i = 0; i <= 1000; ++i)
+    {
+      int idx = rand () % array_length (handles);
+      void *handle = handles[idx];
+      if (handle == NULL)
+        {
+          char *name = dso_name (idx);
+          handles[idx] = xdlopen (name, RTLD_LAZY);
+          free (name);
+        }
+      else
+        {
+          handles[idx] = NULL;
+          xdlclose (handle);
+        }
+    }
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  xpthread_barrier_init (&barrier, NULL, 2);
+  pthread_t thr_fork = xpthread_create (NULL, forking_thread, NULL);
+  pthread_t thr_dlopen = xpthread_create (NULL, dlopen_thread, NULL);
+  xpthread_join (thr_dlopen);
+  requested_exit = true;
+  xpthread_join (thr_fork);
+  return 0;
+}
+
+#include <support/test-driver.c>