[basic-improvements] VxWorks thread support

[Zack Weinberg <zack at codesourcery dot com>]

This patch reinstates support for threading under VxWorks.  It is not
complete - one must also add a chunk of code to the operating system.
More on that in a separate message.

I am open to better suggestions for how to deal with t-vxworks and
t-ppccomm fighting over LIB2FUNCS_EXTRA.

Tested by building a i686-linux -> powerpc-vxworks cross compiler, C
and C++ only, including a build of libgcc.a.  I haven't yet verified
that the binutils powerpc-vxworks is sane, so the assembler and linker
were configured for a powerpc-eabisim target.  (That verification is
next on my list.)

Applied to basic-improvements branch.

zw

	* gthr-vxworks.h: Rewritten from scratch.
	* config/vxlib.c: New file.
	* config/t-vxworks: Add config/vxlib.c to LIB2FUNCS_EXTRA.
	* config/rs6000/t-vxworks: Add config/vxlib.c to
	LIB2FUNCS_EXTRA here too, because of clash with
	config/rs6000/t-ppccomm.

===================================================================
Index: gthr-vxworks.h
--- gthr-vxworks.h	29 Oct 2002 05:08:20 -0000	1.10.20.1
+++ gthr-vxworks.h	5 Nov 2002 05:38:29 -0000
@@ -30,7 +30,74 @@ Software Foundation, 59 Temple Place - S
 #ifndef GCC_GTHR_VXWORKS_H
 #define GCC_GTHR_VXWORKS_H
 
-/* Temporarily on hiatus.  */
-#include "gthr-single.h"
+#ifdef _LIBOBJC
 
-#endif
+/* libobjc requires the optional pthreads component.  */
+#include "gthr-posix.h"
+
+#else
+
+#define __GTHREADS 1
+#define __gthread_active_p() 1
+
+/* Mutexes are easy, except that they need to be initialized at runtime.  */
+
+#include <semLib.h>
+
+typedef SEM_ID __gthread_mutex_t;
+#define __GTHREAD_MUTEX_INIT_FUNCTION __gthread_mutex_init_function
+
+static inline void
+__gthread_mutex_init_function (__gthread_mutex_t *mutex)
+{
+  *mutex = semMCreate (SEM_Q_PRIORITY | SEM_INVERSION_SAFE | SEM_DELETE_SAFE);
+}
+
+static inline int
+__gthread_mutex_lock (__gthread_mutex_t *mutex)
+{
+  return semTake (*mutex, WAIT_FOREVER);
+}
+
+static inline int
+__gthread_mutex_trylock (__gthread_mutex_t *mutex)
+{
+  return semTake (*mutex, NO_WAIT);
+}
+
+static inline int
+__gthread_mutex_unlock (__gthread_mutex_t *mutex)
+{
+  return semGive (*mutex);
+}
+
+/* pthread_once is complicated enough that it's implemented
+   out-of-line.  See config/vxlib.c.  */
+
+typedef struct
+{
+  volatile unsigned char busy;
+  volatile unsigned char done;
+}
+__gthread_once_t;
+
+#define __GTHREAD_ONCE_INIT { 0, 0 }
+
+extern int __gthread_once (__gthread_once_t *once, void (*func)(void));
+
+/* Thread-specific data requires a great deal of effort, since VxWorks
+   is not really set up for it.  See config/vxlib.c for the gory
+   details.  All the TSD routines are sufficiently complex that they
+   need to be implemented out of line.  */
+
+typedef unsigned int __gthread_key_t;
+
+extern int __gthread_key_create (__gthread_key_t *keyp, void (*dtor)(void *));
+extern int __gthread_key_delete (__gthread_key_t key);
+
+extern void *__gthread_getspecific (__gthread_key_t key);
+extern int __gthread_setspecific (__gthread_key_t key, void *ptr);
+
+#endif /* not _LIBOBJC */
+
+#endif /* gthr-vxworks.h */
===================================================================
Index: config/t-vxworks
--- config/t-vxworks	29 Oct 2002 08:09:20 -0000	1.1.2.1
+++ config/t-vxworks	5 Nov 2002 05:38:29 -0000
@@ -15,6 +15,9 @@ TARGET_LIBGCC2_CFLAGS =
 # Don't build libgcc.a with debug info
 LIBGCC2_DEBUG_CFLAGS =
 
+# Extra libgcc2 module used by gthr-vxworks.h functions
+LIB2FUNCS_EXTRA = $(srcdir)/config/vxlib.c
+
 # This ensures that the correct target headers are used; some
 # VxWorks system headers have names that collide with GCC's
 # internal (host) headers, e.g. regs.h.
===================================================================
Index: config/vxlib.c
--- config/vxlib.c	1 Jan 1970 00:00:00 -0000
+++ config/vxlib.c	5 Nov 2002 05:38:29 -0000
@@ -0,0 +1,310 @@
+/* Copyright (C) 2002 Free Software Foundation, Inc.
+   Contributed by Zack Weinberg <zack@codesourcery.com>
+
+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.  */
+
+/* Threads compatibility routines for libgcc2 for VxWorks.
+   These are out-of-line routines called from gthr-vxworks.h.  */
+
+/* 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.  */
+
+#include "tconfig.h"
+#include "tsystem.h"
+#include "gthr.h"
+
+#include <vxWorks.h>
+#include <vxLib.h>
+#include <taskLib.h>
+#include <taskHookLib.h>
+
+/* Init-once operation.
+
+   This would be a clone of the implementation from gthr-solaris.h,
+   except that we have a bootstrap problem - the whole point of this
+   exercise is to prevent double initialization, but if two threads
+   are racing with each other, once->mutex is liable to be initialized
+   by both.  Then each thread will lock its own mutex, and proceed to
+   call the initialization routine.
+
+   So instead we use a bare atomic primitive (vxTas()) to handle
+   mutual exclusion.  Threads losing the race then busy-wait, calling
+   taskDelay() to yield the processor, until the initialization is
+   completed.  Inefficient, but reliable.  */
+
+int
+__gthread_once (__gthread_once_t *guard, void (*func)(void))
+{
+  if (guard->done)
+    return 0;
+
+  while (!vxTas ((void *)&guard->busy))
+    taskDelay (1);
+
+  /* Only one thread at a time gets here.  Check ->done again, then
+     go ahead and call func() if no one has done it yet.  */
+  if (!guard->done)
+    {
+      func ();
+      guard->done = 1;
+    }
+
+  guard->busy = 0;
+  return 0;
+}
+
+/* Thread-specific data.
+
+   We reserve a field in the TCB to point to a dynamically allocated
+   array which is used to store TSD values.  A TSD key is simply an
+   offset in this array.  The exact location of the TCB field is not
+   known to this code nor to vxlib.c -- all access to it indirects
+   through the routines __gthread_get_tsd_data and
+   __gthread_set_tsd_data, which are provided by the VxWorks kernel.
+
+   There is also a global array which records which keys are valid and
+   which have destructors.
+
+   A task delete hook is installed to execute key destructors.  The
+   routines __gthread_enter_tsd_dtor_context and
+   __gthread_leave_tsd_dtor_context, which are also provided by the
+   kernel, ensure that it is safe to call free() on memory allocated
+   by the task being deleted.  (This is a no-op on VxWorks 5, but
+   a major undertaking on AE.)
+
+   Since this interface is used to allocate only a small number of
+   keys, the table size is small and static, which simplifies the
+   code quite a bit.  Revisit this if and when it becomes necessary.  */
+
+#define MAX_KEYS 4
+
+/* This is the structure pointed to by the pointer returned
+   by __gthread_get_tsd_data.  It must match the definition
+   in the kernel file defining __gthread_get_tsd_data.  */
+struct tsd_data
+{
+  void *values[MAX_KEYS];
+};
+
+
+/* kernel provided routines */
+extern void *__gthread_get_tsd_data (WIND_TCB *tcb);
+extern void __gthread_set_tsd_data (WIND_TCB *tcb, void *data);
+
+extern void __gthread_enter_tsd_dtor_context (WIND_TCB *tcb);
+extern void __gthread_leave_tsd_dtor_context (WIND_TCB *tcb);
+
+typedef void (*fet_callback_t) (WIND_TCB *, unsigned int);
+extern void __gthread_for_all_tasks (fet_callback_t fun, unsigned int number);
+
+/* This is a global structure which records all of the active keys.  A
+   key with NULL dtor is valid; a key with dtor == (void (*)(void))-1
+   is valid, but has no dtor.  */
+
+typedef void (*tsd_dtor) (void *);
+static tsd_dtor tsd_dtors[MAX_KEYS];
+#define KEY_INVALID ((tsd_dtor) 0)
+#define KEY_NO_DTOR ((tsd_dtor) -1)
+
+static __gthread_once_t tsd_init_guard = __GTHREAD_ONCE_INIT;
+static __gthread_mutex_t tsd_lock;
+
+/* Internal routines.  */
+
+/* The task TCB has just been deleted.  Call the destructor
+   function for each TSD key that has both a destructor and
+   a non-NULL specific value in this thread.  */
+
+static void
+tsd_delete_hook (WIND_TCB *tcb)
+{
+  struct tsd_data *data = __gthread_get_tsd_data (tcb);
+  __gthread_key_t key;
+
+  if (data)
+    {
+      __gthread_enter_tsd_dtor_context (tcb);
+      for (key = 0; key < MAX_KEYS; key++)
+	{
+	  if (tsd_dtors[key] == KEY_INVALID || tsd_dtors[key] == KEY_NO_DTOR)
+	    continue;
+	  if (data->values[key])
+	    tsd_dtors[key] (data->values[key]);
+	}
+      free (data);
+      __gthread_set_tsd_data (tcb, 0);
+      __gthread_leave_tsd_dtor_context (tcb);
+    }
+} 
+
+/* Initialize global data used by the TSD system.  */
+static void
+tsd_init (void)
+{
+  taskDeleteHookAdd ((FUNCPTR)tsd_delete_hook);
+  __GTHREAD_MUTEX_INIT_FUNCTION (&tsd_lock);
+}
+
+/* External interface */
+
+/* Store in KEYP a value which can be passed to __gthread_setspecific/
+   __gthread_getspecific to store and retrive a value which is
+   specific to each calling thread.  If DTOR is not NULL, it will be
+   called when a thread terminates with a non-NULL specific value for
+   this key, with the value as its sole argument.  */
+
+int
+__gthread_key_create (__gthread_key_t *keyp, tsd_dtor dtor)
+{
+  __gthread_key_t key;
+
+  __gthread_once (&tsd_init_guard, tsd_init);
+
+  if (__gthread_mutex_lock (&tsd_lock) == ERROR)
+    return errno;
+
+  for (key = 0; key < MAX_KEYS; key++)
+    if (tsd_dtors[key] == KEY_INVALID)
+      goto found_slot;
+
+  /* no room */
+  __gthread_mutex_unlock (&tsd_lock);
+  return EAGAIN;
+
+ found_slot:
+  tsd_dtors[key] = dtor ? dtor : KEY_NO_DTOR;
+  *keyp = key;
+  __gthread_mutex_unlock (&tsd_lock);
+  return 0;
+}
+
+/* Subroutine of __gthread_key_delete.  Clear the thread-specific
+   value associated with key INDEX in TCB.  */
+
+static void
+key_delete_iter (WIND_TCB *tcb, unsigned int index)
+{
+  struct tsd_data *data = __gthread_get_tsd_data (tcb);
+  if (data)
+    data->values[index] = 0;
+}
+
+/* Invalidate KEY; it can no longer be used as an argument to
+   setspecific/getspecific.  Note that this does NOT call destructor
+   functions for any live values for this key.  */
+int
+__gthread_key_delete (__gthread_key_t key)
+{
+  if (key >= MAX_KEYS)
+    return EINVAL;
+
+  __gthread_once (&tsd_init_guard, tsd_init);
+
+  if (__gthread_mutex_lock (&tsd_lock) == ERROR)
+    return errno;
+
+  if (tsd_dtors[key] == KEY_INVALID)
+    {
+      __gthread_mutex_unlock (&tsd_lock);
+      return EINVAL;
+    }
+
+  __gthread_for_all_tasks (key_delete_iter, key);
+
+  tsd_dtors[key] = KEY_INVALID;
+
+  __gthread_mutex_unlock (&tsd_lock);
+  return 0;
+}
+
+/* Retrieve the thread-specific value for KEY.  If it has never been
+   set in this thread, or KEY is invalid, returns NULL.
+
+   It does not matter if this function races with key_create or
+   key_delete; the worst that can happen is you get a value other than
+   the one that a serialized implementation would have provided.  */
+
+void *
+__gthread_getspecific (__gthread_key_t key)
+{
+  struct tsd_data *data;
+
+  if (key >= MAX_KEYS || tsd_dtors[key] == KEY_INVALID)
+    return 0;
+
+  data = __gthread_get_tsd_data (taskTcb (taskIdSelf ()));
+
+  if (data)
+    return data->values[key];
+  else
+    return 0;
+}
+
+/* Set the thread-specific value for KEY.  If KEY is invalid, or
+   memory allocation fails, returns -1, otherwise 0.
+
+   It does matter if this function races with key_create/key_delete,
+   so we have to take the lock, which should be okay since this is
+   called much less often than getspecific (usually once per key
+   per thread).  */
+
+int
+__gthread_setspecific (__gthread_key_t key, void *value)
+{
+  struct tsd_data *data;
+  WIND_TCB *tcb;
+
+  if (key >= MAX_KEYS)
+    return EINVAL;
+
+  __gthread_once (&tsd_init_guard, tsd_init);
+
+  if (__gthread_mutex_lock (&tsd_lock) == ERROR)
+    return errno;
+
+  if (tsd_dtors[key] == KEY_INVALID)
+    {
+      __gthread_mutex_unlock (&tsd_lock);
+      return EINVAL;
+    }
+
+  tcb = taskTcb (taskIdSelf ());
+  data = __gthread_get_tsd_data (tcb);
+  if (!data)
+    {
+      data = calloc (MAX_KEYS, sizeof (void *));
+      if (!data)
+	{
+	  __gthread_mutex_unlock (&tsd_lock);
+	  return ENOMEM;
+	}
+      __gthread_set_tsd_data (tcb, data);
+    }
+
+  data->values[key] = value;
+
+  __gthread_mutex_unlock (&tsd_lock);
+  return 0;
+}
+
+
+
===================================================================
Index: config/rs6000/t-vxworks
--- config/rs6000/t-vxworks	29 Oct 2002 08:09:20 -0000	1.1.2.1
+++ config/rs6000/t-vxworks	5 Nov 2002 05:38:29 -0000
@@ -5,3 +5,6 @@ MULTILIB_DIRNAMES = PPC403gnu PPC405gnu 
 		    PPC603gnu PPC604gnu PPC860gnu
 
 MULTILIB_MATCHES  = t604=
+
+# Put vxlib.c back in LIB2FUNCS_EXTRA (t-ppccomm clobbers it).
+LIB2FUNCS_EXTRA += $(srcdir)/config/vxlib.c