elf: Add test case for [BZ #19329]

Test concurrent dlopen and pthread_create when the loaded modules have
TLS.  This triggers dl-tls assertion failures more reliably than the
nptl/tst-stack4 test.

The dlopened module has 100 DT_NEEDED dependencies with TLS, they were
reused from an existing TLS test. The number of created threads during
dlopen depends on filesystem speed and hardware, but at most 3 threads
are alive at a time to limit resource usage.

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

1 files changed, 68 insertions, 0 deletions

diff --git a/elf/tst-tls21.c b/elf/tst-tls21.c
new file mode 100644
index 0000000000..560bf5813a
--- /dev/null
+++ b/elf/tst-tls21.c
@@ -0,0 +1,68 @@
+/* Test concurrent dlopen and pthread_create: BZ 19329.
+   Copyright (C) 2021 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <dlfcn.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <stdatomic.h>
+#include <support/xdlfcn.h>
+#include <support/xthread.h>
+
+#define THREADS 10000
+
+static atomic_int done;
+
+static void *
+start (void *a)
+{
+  /* Load a module with many dependencies that each have TLS.  */
+  xdlopen ("tst-tls21mod.so", RTLD_LAZY);
+  atomic_store_explicit (&done, 1, memory_order_release);
+  return 0;
+}
+
+static void *
+nop (void *a)
+{
+  return 0;
+}
+
+static int
+do_test (void)
+{
+  pthread_t t1, t2;
+  int i;
+
+  /* Load a module with lots of dependencies and TLS.  */
+  t1 = xpthread_create (0, start, 0);
+
+  /* Concurrently create lots of threads until dlopen is observably done.  */
+  for (i = 0; i < THREADS; i++)
+    {
+      if (atomic_load_explicit (&done, memory_order_acquire) != 0)
+	break;
+      t2 = xpthread_create (0, nop, 0);
+      xpthread_join (t2);
+    }
+
+  xpthread_join (t1);
+  printf ("threads created during dlopen: %d\n", i);
+  return 0;
+}
+
+#include <support/test-driver.c>