Re: Applied: PATCH for thread-safe C++ static local initialization

["Joel Sherrill <joel at OARcorp dot com>" <joel dot sherrill at OARcorp dot com>]

Jason Merrill wrote:
> Here's the patch I'm applying.  The major change in this version is that
> instead of emulating a recursive mutex in the libsupc++ code, I added
> recursive mutex support to gthr.  I implemented it for most of the thread
> targets; I didn't implement it for rtems, though, which relies on OS hooks.
> I suppose I could implement it there in terms of the current hooks, but
> thought I'd leave that decision to the rtems folks (hi, Joel!).  I tried to
> test on solaris and dce threads, but failed for various reasons; I would
> appreciate testing and feedback on all non-posix thread targets.

Sorry for the delay.  I took some time off.

If I understand the intent, this looks easy for RTEMS.  I have attached
a modified gthr-rtems.h (not compiled yet) which should come close to
making the RTEMS GCC part right.

The second step requires some information on your intended use of this
mutex.  RTEMS allows pretty fine grained control over mutex attributes.
I just to make sure we have the right attributes on the mutexes.

Currently, the regular gcc mutex uses priority blocking and
priority inheritance protocol when there is contention and blocking.
But it does not allow nesting.

 + Is this really the right mutex attributes for GCC?
 + Do you just want to use the same attributes plus allow nesting on
   (recursive locking) on this new type of mutex?
 + Would it be wrong to allow nesting on the older type of mutex
   and just make the two types equivalent?

Also what GCC major/minor version should be test to see if
this support is to be included in our adapter file.


--
Joel Sherrill, Ph.D.             Director of Research & Development
joel@OARcorp.com                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
   Support Available             (256) 722-9985

/* RTEMS threads compatibility routines for libgcc2 and libobjc.
   by: Rosimildo da Silva( rdasilva@connecttel.com ) */
/* Compile this one with gcc.  */
/* Copyright (C) 1997, 1999, 2000, 2002, 2003 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

GCC 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 General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

/* As a special exception, if you link this library with other files,
   some of which are compiled with GCC, to produce an executable,
   this library does not by itself cause the resulting executable
   to be covered by the GNU General Public License.
   This exception does not however invalidate any other reasons why
   the executable file might be covered by the GNU General Public License.  */

#ifndef GCC_GTHR_RTEMS_H
#define GCC_GTHR_RTEMS_H

#ifdef __cplusplus
extern "C" {
#endif

#define __GTHREADS 1

#define __GTHREAD_ONCE_INIT  0
#define __GTHREAD_MUTEX_INIT 0
#define __GTHREAD_MUTEX_INIT_FUNCTION  rtems_gxx_mutex_init
#define __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION  rtems_gxx_recursive_mutex_init

/* Avoid dependency on rtems specific headers.  */
typedef void *__gthread_key_t;
typedef int   __gthread_once_t;
typedef void *__gthread_mutex_t;
typedef void *__gthread_recursive_mutex_t;

/*
 * External functions provided by RTEMS. They are very similar to their POSIX
 * counterparts. A "Wrapper API" is being use to avoid dependency on any RTEMS
 * header files.
 */

/* generic per task variables */
extern int rtems_gxx_once (__gthread_once_t *once, void (*func) (void));
extern int rtems_gxx_key_create (__gthread_key_t *key, void (*dtor) (void *));
extern int rtems_gxx_key_delete (__gthread_key_t key);
extern void *rtems_gxx_getspecific (__gthread_key_t key);
extern int rtems_gxx_setspecific (__gthread_key_t key, const void *ptr);

/* mutex support */
extern void rtems_gxx_mutex_init (__gthread_mutex_t *mutex);
extern int rtems_gxx_mutex_lock (__gthread_mutex_t *mutex);
extern int rtems_gxx_mutex_trylock (__gthread_mutex_t *mutex);
extern int rtems_gxx_mutex_unlock (__gthread_mutex_t *mutex);

/* recursive mutex support */
extern void rtems_gxx_recursive_mutex_init (__gthread_recursive_mutex_t *mutex);
extern int rtems_gxx_recursive_mutex_lock (__gthread_recursive_mutex_t *mutex);
extern int rtems_gxx_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex);
extern int rtems_gxx_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex);


/* RTEMS threading is always active */
static inline int
__gthread_active_p (void)
{
  return 1;
}

/* Wrapper calls */
static inline int
__gthread_once (__gthread_once_t *once, void (*func) (void))
{
   return rtems_gxx_once( once, func );
}

static inline int
__gthread_key_create (__gthread_key_t *key, void (*dtor) (void *))
{
  return rtems_gxx_key_create( key, dtor );
}

static inline int
__gthread_key_delete (__gthread_key_t key)
{
  return rtems_gxx_key_delete (key);
}

static inline void *
__gthread_getspecific (__gthread_key_t key)
{
  return rtems_gxx_getspecific (key);
}

static inline int
__gthread_setspecific (__gthread_key_t key, const void *ptr)
{
  return rtems_gxx_setspecific (key, ptr);
}

static inline int
__gthread_mutex_lock (__gthread_mutex_t *mutex)
{
    return rtems_gxx_mutex_lock (mutex);
}

static inline int
__gthread_mutex_trylock (__gthread_mutex_t *mutex)
{
    return rtems_gxx_mutex_trylock (mutex);
}

static inline int
__gthread_mutex_unlock (__gthread_mutex_t *mutex)
{
    return rtems_gxx_mutex_unlock( mutex );
}

static inline int
__gthread_recursive_mutex_lock (__gthread_recursive_mutex_t *mutex)
{
    return rtems_gxx_recursive_mutex_lock (mutex);
}

static inline int
__gthread_recursive_mutex_trylock (__gthread_recursive_mutex_t *mutex)
{
    return rtems_gxx_recursive_mutex_trylock (mutex);
}

static inline int
__gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *mutex)
{
    return rtems_gxx_recursive_mutex_unlock( mutex );
}

#ifdef __cplusplus
}
#endif

#endif /* ! GCC_GTHR_RTEMS_H */