nptl: Disable fork and atfork on MMU-less systems.

They do not work on MMU-less systems.

For atfork, implement a hidden function that always returns EPERM.

	* libpthread/nptl/sysdeps/unix/sysv/linux/fork.c: Disable if
	__ARCH_USE_MMU__ is not defined.
	* libpthread/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c
	(__libc_pthread_init): Handle __ARCH_USE_MMU__.
	* libpthread/nptl/sysdeps/unix/sysv/linux/register-atfork.c: Likewise.
	* libpthread/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c: Likewise.

Signed-off-by: Mickaël Guêné <mickael.guene@st.com>
Signed-off-by: Christophe Lyon <christophe.lyon@st.com>

libpthread/nptl/sysdeps/unix/sysv/linux/fork.c

@@ -28,6 +28,7 @@
 #include <atomic.h>
 #include <errno.h>
 
+#ifdef __ARCH_USE_MMU__
 unsigned long int *__fork_generation_pointer;
 
 
@@ -206,3 +207,5 @@ fork (void)
   return pid;
 }
 libc_hidden_def(fork)
+
+#endif /* __ARCH_USE_MMU__ */

libpthread/nptl/sysdeps/unix/sysv/linux/libc_pthread_init.c

@@ -40,10 +40,14 @@ __libc_pthread_init (
      void (*reclaim) (void))
 {
   /* Remember the pointer to the generation counter in libpthread.  */
+#ifdef __ARCH_USE_MMU__
   __fork_generation_pointer = ptr;
+#endif
 
   /* Called by a child after fork.  */
+#ifdef __ARCH_USE_MMU__
   __register_atfork (NULL, NULL, reclaim, NULL);
+#endif
 
 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
   return &__libc_multiple_threads;

libpthread/nptl/sysdeps/unix/sysv/linux/register-atfork.c

@@ -24,6 +24,7 @@
 #include <tls.h>
 
 
+#ifdef __ARCH_USE_MMU__
 /* Lock to protect allocation and deallocation of fork handlers.  */
 int __fork_lock = LLL_LOCK_INITIALIZER;
 
@@ -118,6 +119,18 @@ __linkin_atfork (struct fork_handler *newp)
   while (catomic_compare_and_exchange_bool_acq (&__fork_handlers,
 						newp, newp->next) != 0);
 }
+#else
+int
+__register_atfork (
+     void (*prepare) (void),
+     void (*parent) (void),
+     void (*child) (void),
+     void *dso_handle)
+{
+    return EPERM;
+}
+libc_hidden_def (__register_atfork)
+#endif
 
 #if 0
 libc_freeres_fn (free_mem)
@@ -145,4 +158,3 @@ libc_freeres_fn (free_mem)
     }
 }
 #endif
-

libpthread/nptl/sysdeps/unix/sysv/linux/unregister-atfork.c

@@ -22,7 +22,7 @@
 #include <atomic.h>
 #include <tls.h>
 
-
+#ifdef __ARCH_USE_MMU__
 void
 __unregister_atfork (
      void *dso_handle)
@@ -120,3 +120,11 @@ __unregister_atfork (
       deleted = deleted->next;
     }
 }
+#else
+void
+__unregister_atfork (
+     void *dso_handle)
+{
+    /* Nothing to do.  */
+}
+#endif