1 files changed, 62 insertions, 0 deletions
diff --git a/REORG.TODO/nptl/pthread_cond_destroy.c b/REORG.TODO/nptl/pthread_cond_destroy.c
new file mode 100644
index 0000000000..fc65dca78c
--- /dev/null
+++ b/REORG.TODO/nptl/pthread_cond_destroy.c
@@ -0,0 +1,62 @@
+/* Copyright (C) 2002-2017 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
+
+   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 <errno.h>
+#include <shlib-compat.h>
+#include "pthreadP.h"
+#include <stap-probe.h>
+#include <atomic.h>
+#include <futex-internal.h>
+
+#include "pthread_cond_common.c"
+
+/* See __pthread_cond_wait for a high-level description of the algorithm.
+
+   A correct program must make sure that no waiters are blocked on the condvar
+   when it is destroyed, and that there are no concurrent signals or
+   broadcasts.  To wake waiters reliably, the program must signal or
+   broadcast while holding the mutex or after having held the mutex.  It must
+   also ensure that no signal or broadcast are still pending to unblock
+   waiters; IOW, because waiters can wake up spuriously, the program must
+   effectively ensure that destruction happens after the execution of those
+   signal or broadcast calls.
+   Thus, we can assume that all waiters that are still accessing the condvar
+   have been woken.  We wait until they have confirmed to have woken up by
+   decrementing __wrefs.  */
+int
+__pthread_cond_destroy (pthread_cond_t *cond)
+{
+  LIBC_PROBE (cond_destroy, 1, cond);
+
+  /* Set the wake request flag.  We could also spin, but destruction that is
+     concurrent with still-active waiters is probably neither common nor
+     performance critical.  Acquire MO to synchronize with waiters confirming
+     that they finished.  */
+  unsigned int wrefs = atomic_fetch_or_acquire (&cond->__data.__wrefs, 4);
+  int private = __condvar_get_private (wrefs);
+  while (wrefs >> 3 != 0)
+    {
+      futex_wait_simple (&cond->__data.__wrefs, wrefs, private);
+      /* See above.  */
+      wrefs = atomic_load_acquire (&cond->__data.__wrefs);
+    }
+  /* The memory the condvar occupies can now be reused.  */
+  return 0;
+}
+versioned_symbol (libpthread, __pthread_cond_destroy,
+		  pthread_cond_destroy, GLIBC_2_3_2);