Merge pull request #585 from ocaml/thread-safety

Thread safety updates

Author: vouillon

lib/mark_infos.ml

@@ -5,7 +5,8 @@ type t = int array
 let make marks =
   let len = 1 + List.fold_left ~f:(fun ma (i, _) -> max ma i) ~init:(-1) marks in
   let t = Array.make len (-1) in
-  List.iter ~f:(fun (i, v) -> t.(i) <- v) marks;
+  let set (i, v) = t.(i) <- v in
+  List.iter ~f:set marks;
   t
 ;;
 

lib/pmark.ml

@@ -3,13 +3,8 @@ module Pmark = struct
 
   let equal (x : int) (y : int) = x = y
   let compare (x : int) (y : int) = compare x y
-  let r = ref 0
-
-  let gen () =
-    incr r;
-    !r
-  ;;
-
+  let r = Atomic.make 1
+  let gen () = Atomic.fetch_and_add r 1
   let pp = Format.pp_print_int
 end
 

lib_test/concurrency/suppress.txt

@@ -16,3 +16,7 @@ race_top:^camlRe__Automata.status
 
 # Race within Compile.final
 race_top:^camlRe__Compile.final
+
+# Spurious data race due to the two-step initialization in Mark_info.make
+# (between Mark_info.make and other functions in module Mark_infos)
+race_top:^camlRe__Mark_infos.set

lib_test/concurrency/test.ml

@@ -81,12 +81,16 @@ let execute ~short re a =
     (inverse_permutation a)
     (Array.map
        (fun i ->
-         try Some (Re.exec ~pos:(if short then 30 - 7 else 0) re strings.(i)) with
+         try
+           Some
+             (Re.Group.all_offset
+              @@ Re.exec ~pos:(if short then 30 - 7 else 0) re strings.(i))
+         with
          | Not_found -> None)
        a)
 ;;
 
-let compare_groups g g' = Re.Group.(all_offset g = all_offset g')
+let compare_groups g g' = g = g'
 
 let concurrent f f' =
   let barrier = Barrier.create 2 in