[PATCH] Tweak test-*exit-race tests to honor the maximum number of processes

["Dmitry V. Levin" <ldv at altlinux dot org>]

When the number of threads created by test-*exit-race tests is close
to the maximum number of simultaneous processes per uid, these tests
fail with the following diagnostics:

error: xpthread_check_return.c:32: pthread_create: Resource temporarily unavailable

Workaround this issue by limiting the number of threads created
by these tests to sysconf (_SC_CHILD_MAX) / 2.

Tested that these tests still fail reliably on x86_64 with glibc-2.26
and sysconf (_SC_CHILD_MAX) == 512.

*  stdlib/test-atexit-race-common.c: Include <unistd.h>.
(kNumThreads): Remove const qualifier.
(do_test): Limit kNumThreads to sysconf (_SC_CHILD_MAX) / 2.
---
 ChangeLog                        |  6 ++++++
 stdlib/test-atexit-race-common.c | 10 ++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/stdlib/test-atexit-race-common.c b/stdlib/test-atexit-race-common.c
index 4d7f911..7a65264 100644
--- a/stdlib/test-atexit-race-common.c
+++ b/stdlib/test-atexit-race-common.c
@@ -33,10 +33,11 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
 #include <support/xthread.h>
 
-const size_t kNumThreads = 1024;
-const size_t kNumHandlers = 1024;
+static size_t kNumThreads = 1024;
+static const size_t kNumHandlers = 1024;
 
 static void *
 threadfunc (void *unused)
@@ -62,6 +63,11 @@ do_test (void)
      128KiB for a maximum required VM size of 128MiB.  */
   xpthread_attr_setstacksize (&attr, 128 * 1024);
 
+  long nproc = sysconf (_SC_CHILD_MAX);
+
+  if (nproc > 0 && nproc / 2 < kNumThreads)
+    kNumThreads = nproc / 2;
+
   for (i = 0; i < kNumThreads; ++i) {
     xpthread_create (&attr, threadfunc, NULL);
   }
-- 
ldv