Index: src/m3core.h
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/m3core.h,v
retrieving revision 1.8
diff -u -r1.8 m3core.h
--- src/m3core.h	19 Mar 2010 17:07:58 -0000	1.8
+++ src/m3core.h	19 Mar 2010 17:08:41 -0000
@@ -404,6 +404,13 @@
 UINT32 __cdecl Uin__htonl(UINT32 x);
 UINT16 __cdecl Uin__htons(UINT16 x);
 
+typedef void (*PThreadForkHandler)(void);
+
+INTEGER
+RTOS__PThreadAtFork(PThreadForkHandler prep,
+                    PThreadForkHandler parent,
+                    PThreadForkHandler child);
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
Index: src/runtime/common/RTCollector.m3
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/runtime/common/RTCollector.m3,v
retrieving revision 1.88
diff -u -r1.88 RTCollector.m3
--- src/runtime/common/RTCollector.m3	15 Dec 2009 19:52:08 -0000	1.88
+++ src/runtime/common/RTCollector.m3	19 Mar 2010 17:08:42 -0000
@@ -2033,19 +2033,31 @@
 
 VAR startedWeakCleaner := FALSE;
 
-PROCEDURE WeakRefFromRef (r: REFANY; p: WeakRefCleanUpProc := NIL): WeakRef =
+PROCEDURE StartWeakCleaner () =
   VAR
     start := FALSE;
-    result: WeakRef;
   BEGIN
-    <* ASSERT r # NIL *>
     TRY
       RTOS.LockHeap();
-      (* create a WeakCleaner thread the first time through *)
-      IF p # NIL AND NOT startedWeakCleaner THEN
+      IF NOT startedWeakCleaner THEN
         start := TRUE;
         startedWeakCleaner := TRUE;
       END;
+    FINALLY
+      RTOS.UnlockHeap();
+    END;
+    IF start THEN
+      EVAL Thread.Fork(NEW(Thread.Closure, apply := WeakCleaner));
+    END;
+  END StartWeakCleaner;
+
+PROCEDURE WeakRefFromRef (r: REFANY; p: WeakRefCleanUpProc := NIL): WeakRef =
+  VAR
+    result: WeakRef;
+  BEGIN
+    <* ASSERT r # NIL *>
+    TRY
+      RTOS.LockHeap();
       (* if necessary, expand weakTable *)
       IF weakFree0 = -1 THEN ExpandWeakTable(); END;
       IF p # NIL THEN
@@ -2075,9 +2087,8 @@
     FINALLY
       RTOS.UnlockHeap();
     END;
-    IF start THEN
-      EVAL Thread.Fork(NEW(Thread.Closure, apply := WeakCleaner));
-    END;
+    (* create a WeakCleaner thread the first time through *)
+    StartWeakCleaner();
     RETURN result;
   END WeakRefFromRef;
 
@@ -2771,8 +2782,24 @@
 
 (*** INITIALIZATION ***)
 
+PROCEDURE PThreadForkChild() =
+  BEGIN
+    IF startedForeground THEN
+      StartBackgroundCollection();
+    END;
+    IF startedBackground THEN
+      StartBackgroundCollection();
+    END;
+    IF startedWeakCleaner THEN
+      StartWeakCleaner();
+    END;
+  END PThreadForkChild;
+
 PROCEDURE Init () =
+  VAR r: INTEGER;
   BEGIN
+    r := RTOS.PThreadAtFork((*prepare*)NIL, (*parent*)NIL, PThreadForkChild);
+    <* ASSERT r = 0 *>
     IF RTParams.IsPresent("paranoidgc") THEN InstallSanityCheck(); END;
     IF RTParams.IsPresent("nogc") THEN disableCount := 1; END;
     IF RTParams.IsPresent("noincremental") THEN incremental := FALSE; END;
Index: src/runtime/common/RTOS.i3
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/runtime/common/RTOS.i3,v
retrieving revision 1.10
diff -u -r1.10 RTOS.i3
--- src/runtime/common/RTOS.i3	8 Sep 2009 05:54:55 -0000	1.10
+++ src/runtime/common/RTOS.i3	19 Mar 2010 17:08:42 -0000
@@ -5,7 +5,7 @@
 (*|      modified on Sun Feb 21 14:15:00 PST 1993 by jdd        *)
 (*|      modified on Wed Jan 27 22:27:27 PST 1993 by mjordan    *)
 
-(* "RTOS" is a private interface that provides the low-level,
+(* "RTOS" is a semi-private interface that provides the low-level,
    OS-specific memory allocation and shutdown routines. *)
 
 INTERFACE RTOS;
@@ -40,4 +40,13 @@
 (* Write the "n" bytes beginning at address "a" to the standard
    error output file or console. *)
 
+(* ThreadF__PThreadAtFork calls pthread_atfork
+ * on pthreads platform, otherwise does nothing.
+ * Return value is from pthread_atform, 0 for success,
+ * always 0 with user threads and Win32 threads.
+ *)
+TYPE PThreadForkHandler = PROCEDURE();
+<* EXTERNAL RTOS__PThreadAtFork *>
+PROCEDURE PThreadAtFork(prep, parent, child: PThreadForkHandler): INTEGER;
+
 END RTOS.
Index: src/runtime/common/m3makefile
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/runtime/common/m3makefile,v
retrieving revision 1.27
diff -u -r1.27 m3makefile
--- src/runtime/common/m3makefile	14 Dec 2009 08:09:48 -0000	1.27
+++ src/runtime/common/m3makefile	19 Mar 2010 17:08:42 -0000
@@ -58,7 +58,7 @@
 Interface ("RTSignal")
 Interface ("RTStack")
 Interface ("RTTypeSRC")
-interface ("RTOS")
+Interface ("RTOS")
 
 proc FileExists(a) is
     return not stale (a, a)
Index: src/thread/POSIX/ThreadPosixC.c
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/thread/POSIX/ThreadPosixC.c,v
retrieving revision 1.32
diff -u -r1.32 ThreadPosixC.c
--- src/thread/POSIX/ThreadPosixC.c	16 Dec 2009 12:21:36 -0000	1.32
+++ src/thread/POSIX/ThreadPosixC.c	19 Mar 2010 17:08:42 -0000
@@ -279,6 +279,14 @@
 #endif
 }
 
+INTEGER
+RTOS__PThreadAtFork(PThreadForkHandler prep,
+                    PThreadForkHandler parent,
+                    PThreadForkHandler child)
+{
+    return 0;
+}
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
Index: src/thread/PTHREAD/ThreadPThread.m3
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/thread/PTHREAD/ThreadPThread.m3,v
retrieving revision 1.233
diff -u -r1.233 ThreadPThread.m3
--- src/thread/PTHREAD/ThreadPThread.m3	18 Mar 2010 11:12:10 -0000	1.233
+++ src/thread/PTHREAD/ThreadPThread.m3	19 Mar 2010 17:08:42 -0000
@@ -6,7 +6,7 @@
 Scheduler, SchedulerPosix, RTOS, RTHooks, ThreadPThread;
 
 IMPORT Cerrno, FloatMode, MutexRep,
-       RTCollectorSRC, RTError, RTHeapRep, RTIO, RTParams,
+       RTCollectorSRC, RTError, RTHeapRep, RTIO, RTOS, RTParams,
        RTPerfTool, RTProcess, ThreadEvent, Time,
        Unix, Utime, Word, Usched,
        Uerror, Uexec;
@@ -1294,18 +1294,18 @@
 
 (*-------------------------------------------------------- Initialization ---*)
 
-PROCEDURE Init ()=
+PROCEDURE InitWithStackBase (stackbase: ADDRESS) =
   VAR
     self: T;
     me: Activation;
   BEGIN
-    InitC(ADR(self));
+    InitC(stackbase);
 
     me := NEW(Activation,
               mutex := pthread_mutex_new(),
               cond := pthread_cond_new());
     InitActivations(me);
-    me.stackbase := ADR(self); (* not quite accurate but hopefully ok *)
+    me.stackbase := stackbase;
     IF me.mutex = NIL OR me.cond = NIL THEN
       Die(ThisLine(), "Thread initialization failed.");
     END;
@@ -1322,8 +1322,48 @@
     IF RTParams.IsPresent("foregroundgc") THEN
       RTCollectorSRC.StartForegroundCollection();
     END;
+  END InitWithStackBase;
+
+PROCEDURE Init ()=
+  VAR r: INTEGER;
+  BEGIN
+    r := RTOS.PThreadAtFork(PThreadAtForkPrepare, PThreadAtForkParent, PThreadAtForkChild);
+    IF r # 0 THEN DieI(ThisLine(), r) END;
+    InitWithStackBase(ADR(r)); (* not quite accurate but hopefully ok *)
   END Init;
 
+VAR locks := ARRAY [0..3] OF pthread_mutex_t{
+			 activeMu, slotsMu, initMu, perfMu};
+
+PROCEDURE PThreadAtForkPrepare() =
+  VAR r: int;
+  BEGIN
+    joinMu.acquire();
+    LockHeap();
+    FOR i := FIRST(locks) TO LAST(locks) DO
+      r := pthread_mutex_lock(locks[i]);
+      IF r # 0 THEN DieI(ThisLine(), r) END;
+    END;
+    (* Walk activations and lock all threads? *)
+  END PThreadAtForkPrepare;
+
+PROCEDURE PThreadAtForkParent() =
+  VAR r: int;
+  BEGIN
+    FOR i := LAST(locks) TO FIRST(locks) BY -1 DO
+      r := pthread_mutex_unlock(locks[i]);
+      IF r # 0 THEN DieI(ThisLine(), r) END;
+    END;
+    UnlockHeap();
+    joinMu.release();
+  END PThreadAtForkParent;
+
+PROCEDURE PThreadAtForkChild() =
+  BEGIN
+    PThreadAtForkParent();
+    InitWithStackBase(GetActivation().stackbase);
+  END PThreadAtForkChild;
+
 (*------------------------------------------------------------- collector ---*)
 (* These procedures provide synchronization primitives for the allocator
    and collector. *)
Index: src/thread/PTHREAD/ThreadPThreadC.c
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/thread/PTHREAD/ThreadPThreadC.c,v
retrieving revision 1.123
diff -u -r1.123 ThreadPThreadC.c
--- src/thread/PTHREAD/ThreadPThreadC.c	25 Feb 2010 08:31:36 -0000	1.123
+++ src/thread/PTHREAD/ThreadPThreadC.c	19 Mar 2010 17:08:42 -0000
@@ -414,6 +414,14 @@
 #endif
 }
 
+INTEGER
+RTOS__PThreadAtFork(PThreadForkHandler prep,
+                    PThreadForkHandler parent,
+                    PThreadForkHandler child)
+{
+    return pthread_atfork(prep, parent, child);
+}
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
Index: src/thread/WIN32/ThreadWin32C.c
===================================================================
RCS file: /usr/cvs/cm3/m3-libs/m3core/src/thread/WIN32/ThreadWin32C.c,v
retrieving revision 1.64
diff -u -r1.64 ThreadWin32C.c
--- src/thread/WIN32/ThreadWin32C.c	16 Jan 2010 12:44:56 -0000	1.64
+++ src/thread/WIN32/ThreadWin32C.c	19 Mar 2010 17:08:42 -0000
@@ -146,6 +146,15 @@
     p(bottom, __getReg(?)); /* bsp? bspstore? try numbers until we find it? */
 #endif
   }
+
+/*-------------------------------------------------------------------------*/
+
+INTEGER
+RTOS__PThreadAtFork(PThreadForkHandler prep,
+                    PThreadForkHandler parent,
+                    PThreadForkHandler child)
+{
+    return 0;
 }
 
 /*-------------------------------------------------------------------------*/