Universe counters on slaves are in sync with master

Simple framework for remote counters.  The slaves ask
the master for a fresh value.  On the master the thread
manager answers with a bunch of fresh values (so that further
requests can be immediately satisfied).
Remote counters are guarded with a mutex on the master,
because all slave managers as well as the master thread
can access the counter at the same time.

I know the name sucks.  These counters are remote for the slaves,
and local for the master.  I'm open to suggestions...

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16713 85f007b7-540e-0410-9357-904b9bb8a0f7

1 files changed, 29 insertions, 0 deletions

diff --git a/lib/remoteCounter.ml b/lib/remoteCounter.ml
new file mode 100644
index 000000000..1983d2722
--- /dev/null
+++ b/lib/remoteCounter.ml
@@ -0,0 +1,29 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2012     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+type 'a getter = unit -> 'a
+type 'a installer = ('a getter) -> unit
+
+let new_counter a ~incr ~build =
+  let data = ref a in
+  let m = Mutex.create () in
+  let mk_thsafe_getter f () =
+    (* - slaves must use a remote counter getter, not this one! *)
+    (* - in the main process there is a race condition between slave
+         managers (that are threads) and the main thread, hence the mutex *)
+    if !Flags.coq_slave_mode > 0 then
+      Errors.anomaly(Pp.str"Slave processes must install remote counters");
+    Mutex.lock m; let x = f () in Mutex.unlock m;
+    build x in
+  let getter = ref (mk_thsafe_getter (fun () -> data := incr !data; !data)) in
+  let installer f =
+    if !Flags.coq_slave_mode < 1 then
+      Errors.anomaly(Pp.str"Only slave processes can install a remote counter")
+    else getter := f in
+  (fun () -> !getter ()), installer
+