[PATCH] Fix PR49484, gthr requirements update (target maintainers have a looksee)

[Richard Guenther <rguenther at suse dot de>]

This fixes PR49484 by protecting __gcov_flush against concurrent
execution.  To be able to use the gthread facility I have to
introduce the requirement that __GTHREAD_MUTEX_INIT_FUNCTION
is always available, even if __GTHREAD_MUTEX_INIT is available as
otherwise no dynamic initialization of a mutex is possible.
I have adjusted gthr-posix.h and gthr-single.h only - target
maintainers, please update your ports accordingly in advance.

Boostrap and regtest on x86_64-unknown-linux-gnu is ongoing,
but this looks like something for stage1 anyway.

Richard.

2012-01-18  Richard Guenther  <rguenther@suse.de>

	* gthr.h (__GTHREAD_MUTEX_INIT_FUNCTION): Adjust specification.
	* gthr-posix.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.
	(__gthread_mutex_init_function): New function.
	* gthr-single.h (__GTHREAD_MUTEX_INIT_FUNCTION): Define.

	PR gcov/49484
	* libgcov.c: Include gthr.h.
	(__gcov_flush_mx): New global variable.
	(init_mx, init_mx_once): New functions.
	(__gcov_flush): Protect self with a mutex.
	(__gcov_fork): Re-initialize mutex after forking.
	* unwind-dw2-fde.c: Change condition under which to use
	__GTHREAD_MUTEX_INIT_FUNCTION.

Index: libgcc/libgcov.c
===================================================================
*** libgcc/libgcov.c	(revision 183270)
--- libgcc/libgcov.c	(working copy)
*************** see the files COPYING3 and COPYING.RUNTI
*** 30,35 ****
--- 30,36 ----
  #include "coretypes.h"
  #include "tm.h"
  #include "libgcc_tm.h"
+ #include "gthr.h"
  
  #if defined(inhibit_libc)
  #define IN_LIBGCOV (-1)
*************** __gcov_init (struct gcov_info *info)
*** 705,710 ****
--- 706,730 ----
    info->version = 0;
  }
  
+ #ifdef __GTHREAD_MUTEX_INIT
+ ATTRIBUTE_HIDDEN __gthread_mutex_t __gcov_flush_mx = __GTHREAD_MUTEX_INIT;
+ #define init_mx_once()
+ #else
+ __gthread_mutex_t __gcov_flush_mx ATTRIBUTE_HIDDEN;
+ 
+ static void
+ init_mx (void)
+ {
+   __GTHREAD_MUTEX_INIT_FUNCTION (&mx);
+ }
+ static void
+ init_mx_once (void)
+ {
+   static __gthread_once_t once = __GTHREAD_ONCE_INIT;
+   __gthread_once (&once, init_mx);
+ }
+ #endif
+ 
  /* Called before fork or exec - write out profile information gathered so
     far and reset it to zero.  This avoids duplication or loss of the
     profile information gathered so far.  */
*************** __gcov_flush (void)
*** 714,719 ****
--- 734,742 ----
  {
    const struct gcov_info *gi_ptr;
  
+   init_mx_once ();
+   __gthread_mutex_lock (&__gcov_flush_mx);
+ 
    gcov_exit ();
    for (gi_ptr = gcov_list; gi_ptr; gi_ptr = gi_ptr->next)
      {
*************** __gcov_flush (void)
*** 737,742 ****
--- 760,767 ----
  	    }
  	}
      }
+ 
+   __gthread_mutex_unlock (&__gcov_flush_mx);
  }
  
  #endif /* L_gcov */
*************** __gcov_ior_profiler (gcov_type *counters
*** 975,982 ****
  pid_t
  __gcov_fork (void)
  {
    __gcov_flush ();
!   return fork ();
  }
  #endif
  
--- 1000,1012 ----
  pid_t
  __gcov_fork (void)
  {
+   pid_t pid;
+   extern __gthread_mutex_t __gcov_flush_mx;
    __gcov_flush ();
!   pid = fork ();
!   if (pid == 0)
!     __GTHREAD_MUTEX_INIT_FUNCTION (&__gcov_flush_mx);
!   return pid;
  }
  #endif
  
Index: libgcc/unwind-dw2-fde.c
===================================================================
*** libgcc/unwind-dw2-fde.c	(revision 183270)
--- libgcc/unwind-dw2-fde.c	(working copy)
*************** static struct object *seen_objects;
*** 47,57 ****
  
  #ifdef __GTHREAD_MUTEX_INIT
  static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;
  #else
  static __gthread_mutex_t object_mutex;
- #endif
  
- #ifdef __GTHREAD_MUTEX_INIT_FUNCTION
  static void
  init_object_mutex (void)
  {
--- 47,56 ----
  
  #ifdef __GTHREAD_MUTEX_INIT
  static __gthread_mutex_t object_mutex = __GTHREAD_MUTEX_INIT;
+ #define init_object_mutex_once()
  #else
  static __gthread_mutex_t object_mutex;
  
  static void
  init_object_mutex (void)
  {
*************** init_object_mutex_once (void)
*** 64,71 ****
    static __gthread_once_t once = __GTHREAD_ONCE_INIT;
    __gthread_once (&once, init_object_mutex);
  }
- #else
- #define init_object_mutex_once()
  #endif
  
  /* Called from crtbegin.o to register the unwind info for an object.  */
--- 63,68 ----
Index: libgcc/gthr-posix.h
===================================================================
*** libgcc/gthr-posix.h	(revision 183270)
--- libgcc/gthr-posix.h	(working copy)
*************** typedef struct timespec __gthread_time_t
*** 63,68 ****
--- 63,69 ----
  #define __GTHREAD_HAS_COND	1
  
  #define __GTHREAD_MUTEX_INIT PTHREAD_MUTEX_INITIALIZER
+ #define __GTHREAD_MUTEX_INIT_FUNCTION __gthread_mutex_init_function
  #define __GTHREAD_ONCE_INIT PTHREAD_ONCE_INIT
  #if defined(PTHREAD_RECURSIVE_MUTEX_INITIALIZER)
  #define __GTHREAD_RECURSIVE_MUTEX_INIT PTHREAD_RECURSIVE_MUTEX_INITIALIZER
*************** __gthread_setspecific (__gthread_key_t _
*** 731,736 ****
--- 732,745 ----
  }
  
  static inline int
+ __gthread_mutex_init_function (__gthread_mutex_t *__mutex)
+ {
+   if (__gthread_active_p ())
+     return __gthrw_(pthread_mutex_init) (__mutex, NULL);
+   return 0;
+ }
+ 
+ static inline int
  __gthread_mutex_destroy (__gthread_mutex_t *__mutex)
  {
    if (__gthread_active_p ())
Index: libgcc/gthr-single.h
===================================================================
*** libgcc/gthr-single.h	(revision 183270)
--- libgcc/gthr-single.h	(working copy)
*************** typedef int __gthread_recursive_mutex_t;
*** 36,41 ****
--- 36,42 ----
  
  #define __GTHREAD_ONCE_INIT 0
  #define __GTHREAD_MUTEX_INIT 0
+ #define __GTHREAD_MUTEX_INIT_FUNCTION (mx)
  #define __GTHREAD_RECURSIVE_MUTEX_INIT 0
  
  #define UNUSED __attribute__((unused))
Index: libgcc/gthr.h
===================================================================
--- libgcc/gthr.h	(revision 183270)
+++ libgcc/gthr.h	(working copy)
@@ -52,11 +52,12 @@ see the files COPYING3 and COPYING.RUNTI
      		to initialize __gthread_mutex_t to get a fast
 		non-recursive mutex.
      __GTHREAD_MUTEX_INIT_FUNCTION
-     		some systems can't initialize a mutex without a
-		function call.  On such systems, define this to a
-		function which looks like this:
+		to initialize __gthread_mutex_t to get a fast
+		non-recursive mutex.
+		Define this to a function which looks like this:
 		  void __GTHREAD_MUTEX_INIT_FUNCTION (__gthread_mutex_t *)
-		Don't define __GTHREAD_MUTEX_INIT in this case
+     		Some systems can't initialize a mutex without a
+		function call.  Don't define __GTHREAD_MUTEX_INIT in this case.
      __GTHREAD_RECURSIVE_MUTEX_INIT
      __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION
      		as above, but for a recursive mutex.