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, 121 insertions, 0 deletions

diff --git a/REORG.TODO/nptl/unregister-atfork.c b/REORG.TODO/nptl/unregister-atfork.c
new file mode 100644
index 0000000000..1eb11d60c6
--- /dev/null
+++ b/REORG.TODO/nptl/unregister-atfork.c
@@ -0,0 +1,121 @@
+/* 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 <stdlib.h>
+#include <fork.h>
+#include <atomic.h>
+#include <futex-internal.h>
+
+
+void
+__unregister_atfork (void *dso_handle)
+{
+  /* Check whether there is any entry in the list which we have to
+     remove.  It is likely that this is not the case so don't bother
+     getting the lock.
+
+     We do not worry about other threads adding entries for this DSO
+     right this moment.  If this happens this is a race and we can do
+     whatever we please.  The program will crash anyway seen.  */
+  struct fork_handler *runp = __fork_handlers;
+  struct fork_handler *lastp = NULL;
+
+  while (runp != NULL)
+    if (runp->dso_handle == dso_handle)
+      break;
+    else
+      {
+	lastp = runp;
+	runp = runp->next;
+      }
+
+  if (runp == NULL)
+    /* Nothing to do.  */
+    return;
+
+  /* Get the lock to not conflict with additions or deletions.  Note
+     that there couldn't have been another thread deleting something.
+     The __unregister_atfork function is only called from the
+     dlclose() code which itself serializes the operations.  */
+  lll_lock (__fork_lock, LLL_PRIVATE);
+
+  /* We have to create a new list with all the entries we don't remove.  */
+  struct deleted_handler
+  {
+    struct fork_handler *handler;
+    struct deleted_handler *next;
+  } *deleted = NULL;
+
+  /* Remove the entries for the DSO which is unloaded from the list.
+     It's a single linked list so readers are.  */
+  do
+    {
+    again:
+      if (runp->dso_handle == dso_handle)
+	{
+	  if (lastp == NULL)
+	    {
+	      /* We have to use an atomic operation here because
+		 __linkin_atfork also uses one.  */
+	      if (catomic_compare_and_exchange_bool_acq (&__fork_handlers,
+							 runp->next, runp)
+		  != 0)
+		{
+		  runp = __fork_handlers;
+		  goto again;
+		}
+	    }
+	  else
+	    lastp->next = runp->next;
+
+	  /* We cannot overwrite the ->next element now.  Put the deleted
+	     entries in a separate list.  */
+	  struct deleted_handler *newp = alloca (sizeof (*newp));
+	  newp->handler = runp;
+	  newp->next = deleted;
+	  deleted = newp;
+	}
+      else
+	lastp = runp;
+
+      runp = runp->next;
+    }
+  while (runp != NULL);
+
+  /* Release the lock.  */
+  lll_unlock (__fork_lock, LLL_PRIVATE);
+
+  /* Walk the list of all entries which have to be deleted.  */
+  while (deleted != NULL)
+    {
+      /* We need to be informed by possible current users.  */
+      deleted->handler->need_signal = 1;
+      /* Make sure this gets written out first.  */
+      atomic_write_barrier ();
+
+      /* Decrement the reference counter.  If it does not reach zero
+	 wait for the last user.  */
+      atomic_decrement (&deleted->handler->refcntr);
+      unsigned int val;
+      while ((val = deleted->handler->refcntr) != 0)
+	futex_wait_simple (&deleted->handler->refcntr, val, FUTEX_PRIVATE);
+
+      deleted = deleted->next;
+    }
+}