2019-02-08  Florian Weimer  <fweimer@redhat.com>

	[BZ #24161]
	* sysdeps/nptl/fork.h (__run_fork_handlers): Add multiple_threads
	argument.
	* nptl/register-atfork.c (__run_fork_handlers): Only perform
	locking if the new do_locking argument is true.
	* sysdeps/nptl/fork.c (__libc_fork): Pass multiple_threads to
	__run_fork_handlers.

Index: glibc-2.29/nptl/register-atfork.c
===================================================================
--- glibc-2.29.orig/nptl/register-atfork.c
+++ glibc-2.29/nptl/register-atfork.c
@@ -107,13 +107,14 @@ __unregister_atfork (void *dso_handle)
 }
 
 void
-__run_fork_handlers (enum __run_fork_handler_type who)
+__run_fork_handlers (enum __run_fork_handler_type who, _Bool do_locking)
 {
   struct fork_handler *runp;
 
   if (who == atfork_run_prepare)
     {
-      lll_lock (atfork_lock, LLL_PRIVATE);
+      if (do_locking)
+	lll_lock (atfork_lock, LLL_PRIVATE);
       size_t sl = fork_handler_list_size (&fork_handlers);
       for (size_t i = sl; i > 0; i--)
 	{
@@ -133,7 +134,8 @@ __run_fork_handlers (enum __run_fork_han
 	  else if (who == atfork_run_parent && runp->parent_handler)
 	    runp->parent_handler ();
 	}
-      lll_unlock (atfork_lock, LLL_PRIVATE);
+      if (do_locking)
+	lll_unlock (atfork_lock, LLL_PRIVATE);
     }
 }
 
Index: glibc-2.29/sysdeps/nptl/fork.c
===================================================================
--- glibc-2.29.orig/sysdeps/nptl/fork.c
+++ glibc-2.29/sysdeps/nptl/fork.c
@@ -55,7 +55,7 @@ __libc_fork (void)
      but our current fork implementation is not.  */
   bool multiple_threads = THREAD_GETMEM (THREAD_SELF, header.multiple_threads);
 
-  __run_fork_handlers (atfork_run_prepare);
+  __run_fork_handlers (atfork_run_prepare, multiple_threads);
 
   /* If we are not running multiple threads, we do not have to
      preserve lock state.  If fork runs from a signal handler, only
@@ -134,7 +134,7 @@ __libc_fork (void)
       __rtld_lock_initialize (GL(dl_load_lock));
 
       /* Run the handlers registered for the child.  */
-      __run_fork_handlers (atfork_run_child);
+      __run_fork_handlers (atfork_run_child, multiple_threads);
     }
   else
     {
@@ -149,7 +149,7 @@ __libc_fork (void)
 	}
 
       /* Run the handlers registered for the parent.  */
-      __run_fork_handlers (atfork_run_parent);
+      __run_fork_handlers (atfork_run_parent, multiple_threads);
     }
 
   return pid;
Index: glibc-2.29/sysdeps/nptl/fork.h
===================================================================
--- glibc-2.29.orig/sysdeps/nptl/fork.h
+++ glibc-2.29/sysdeps/nptl/fork.h
@@ -52,9 +52,11 @@ enum __run_fork_handler_type
    - atfork_run_child: run all the CHILD_HANDLER and unlocks the internal
 		       lock.
    - atfork_run_parent: run all the PARENT_HANDLER and unlocks the internal
-			lock.  */
-extern void __run_fork_handlers (enum __run_fork_handler_type who)
-  attribute_hidden;
+			lock.
+
+   Perform locking only if DO_LOCKING.  */
+extern void __run_fork_handlers (enum __run_fork_handler_type who,
+				 _Bool do_locking) attribute_hidden;
 
 /* C library side function to register new fork handlers.  */
 extern int __register_atfork (void (*__prepare) (void),