Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

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);