Subj : Re: Can C++ local static objects be made thread safe?
To   : comp.programming.threads
From : SenderX
Date : Sat Jan 22 2005 07:20 pm

> Your "7: ..." inside synchronized region is pointless.

Doh! Yes it is.


> And, again,
> your linuxoidic notation to express unidirectional constraints is
> just awful.

Humm. How about:


/*
sink-store barrier
   extern void ac_cpu_i686_mb_store_ssb
   ( void**, void* )
*/
align 16
ac_cpu_i686_mb_store_ssb PROC
 mov ecx, [esp + 4]
 mov eax, [esp + 8]
 sfence
 mov [ecx], eax
 ret
ac_cpu_i686_mb_store_ssb ENDP


/*
hoist-load barrier with dd "hint"
   extern void* ac_cpu_i686_mb_load_ddhlb
   ( void** )
*/
align 16
ac_cpu_i686_mb_load_ddhlb PROC
 mov ecx, [esp + 4]
 mov eax, [ecx]
 lfence
 ret
ac_cpu_i686_mb_load_ddhlb ENDP



/* pseudo-code */


1.  static T *shared = 0;


2.  T *local = ac_cpu_i686_mb_load_ddhlb( &shared );
3.  if ( ! local )
4.  {  ac_mutex_lock( &static_mutex );
5.     if ( ! ( local = shared ) )
6.     {  local = ac_cpu_i686_mb_store_ssb( &shared, new T ); }
7.     ac_mutex_unlock( &static_mutex );
    }


;)

.