[review] support: Add support_set_small_thread_stack_size

diff --git a/support/Makefile b/support/Makefile
index ca238ee..a6081bb 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -63,7 +63,9 @@ 
   support_quote_string \
   support_record_failure \
   support_run_diff \
+  support_set_small_thread_stack_size \
   support_shared_allocate \
+  support_small_stack_thread_attribute \
   support_subprocess \
   support_test_compare_blob \
   support_test_compare_failure \
diff --git a/support/support_set_small_thread_stack_size.c b/support/support_set_small_thread_stack_size.c
new file mode 100644
index 0000000..23189fd
--- /dev/null
+++ b/support/support_set_small_thread_stack_size.c
@@ -0,0 +1,30 @@ 
+/* Set a small stack size, but still large enough for glibc's needs.
+   Copyright (C) 2019 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 <pthread.h>
+#include <support/xthread.h>
+#include <sys/param.h>
+
+void
+support_set_small_thread_stack_size (pthread_attr_t *attr)
+{
+  /* Some architectures have too small values for PTHREAD_STACK_MIN
+     which cannot be used for creating threads.  Ensure that the stack
+     size is at least 256 KiB.  */
+  xpthread_attr_setstacksize (attr, MAX (256 * 1024, PTHREAD_STACK_MIN));
+}
diff --git a/support/support_small_stack_thread_attribute.c b/support/support_small_stack_thread_attribute.c
new file mode 100644
index 0000000..a65097d
--- /dev/null
+++ b/support/support_small_stack_thread_attribute.c
@@ -0,0 +1,54 @@ 
+/* A thread attribute with a small stack.
+   Copyright (C) 2019 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 <support/xthread.h>
+#include <allocate_once.h>
+
+static void *
+allocate (void *closure)
+{
+  pthread_attr_t *result = malloc (sizeof (*result));
+  xpthread_attr_init (result);
+  support_set_small_thread_stack_size (result);
+  return result;
+}
+
+static void
+deallocate (void *ptr, void *closure)
+{
+  xpthread_attr_destroy (ptr);
+  free (ptr);
+}
+
+static void *small_stack_attr;
+
+pthread_attr_t *
+support_small_stack_thread_attribute (void)
+{
+  return allocate_once (&small_stack_attr, allocate, deallocate, NULL);
+}
+
+static void __attribute__ ((destructor))
+fini (void)
+{
+  if (small_stack_attr != NULL)
+    {
+      deallocate (small_stack_attr, NULL);
+      small_stack_attr = NULL;
+    }
+}
diff --git a/support/xthread.h b/support/xthread.h
index 829397c..f39720c 100644
--- a/support/xthread.h
+++ b/support/xthread.h
@@ -75,6 +75,14 @@ 
 void xpthread_attr_setguardsize (pthread_attr_t *attr,
 				 size_t guardsize);
 
+/* Set the stack size in ATTR to a small value, but still large enough
+   to cover most internal glibc stack usage.  */
+void support_set_small_thread_stack_size (pthread_attr_t *attr);
+
+/* Return a pointer to a thread attribute which requests a small
+   stack.  The caller must not free this pointer.  */
+pthread_attr_t *support_small_stack_thread_attribute (void);
+
 /* This function returns non-zero if pthread_barrier_wait returned
    PTHREAD_BARRIER_SERIAL_THREAD.  */
 int xpthread_barrier_wait (pthread_barrier_t *barrier);