Work around for bug in threads + blocking io streamlined

5 files changed, 70 insertions, 26 deletions

diff --git a/lib/cThread.ml b/lib/cThread.ml
new file mode 100644
index 0000000000..a38c88d802
--- /dev/null
+++ b/lib/cThread.ml
@@ -0,0 +1,48 @@
+(************************************************************************)
+(*  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        *)
+(************************************************************************)
+
+let prepare_in_channel_for_thread_friendly_io ic =
+  Unix.set_nonblock (Unix.descr_of_in_channel ic)
+
+let thread_friendly_read_fd fd s ~off ~len =
+  let rec loop () =
+    try Unix.read fd s off len
+    with Unix.Unix_error((Unix.EWOULDBLOCK|Unix.EAGAIN),_,_) ->
+      while not (Thread.wait_timed_read fd 1.0) do Thread.yield () done;
+      loop ()
+  in 
+    loop ()
+
+let thread_friendly_read ic s ~off ~len =
+  try
+    let fd = Unix.descr_of_in_channel ic in
+    thread_friendly_read_fd fd s ~off ~len
+  with Unix.Unix_error _ -> 0
+
+let really_read_fd fd s off len =
+  let i = ref 0 in
+  while !i < len do
+    let off = off + !i in
+    let len = len - !i in
+    let r = thread_friendly_read_fd fd s ~off ~len in
+    if r = 0 then raise End_of_file;
+    i := !i + r
+  done
+
+let thread_friendly_input_value ic =
+  try
+    let fd = Unix.descr_of_in_channel ic in
+    let header = String.create Marshal.header_size in
+    really_read_fd fd header 0 Marshal.header_size;
+    let body_size = Marshal.data_size header 0 in
+    let msg = String.create (body_size + Marshal.header_size) in
+    String.blit header 0 msg 0 Marshal.header_size;
+    really_read_fd fd msg Marshal.header_size body_size;
+    Marshal.from_string msg 0
+  with Unix.Unix_error _ -> raise End_of_file
+
diff --git a/lib/cThread.mli b/lib/cThread.mli
new file mode 100644
index 0000000000..6c635748e9
--- /dev/null
+++ b/lib/cThread.mli
@@ -0,0 +1,21 @@
+(************************************************************************)
+(*  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        *)
+(************************************************************************)
+
+(* As of OCaml 4.01.0 input_value and input do not quite work well
+ * with threads.  The symptom is the following.  Two threads, each
+ * of them blocked on a read (on different channels).  One is not
+ * woken up even if data is available.  When the other one gets data
+ * then the stuck one is eventually unblocked too.  Unix.select with
+ * an unbounded wait has the same problem. *)
+
+(* Use only the following functions on the channel *)
+val prepare_in_channel_for_thread_friendly_io : in_channel -> unit
+val thread_friendly_input_value : in_channel -> 'a
+val thread_friendly_read :
+  in_channel -> string -> off:int -> len:int -> int
+
diff --git a/lib/lib.mllib b/lib/lib.mllib
index be15eca600..9ba1e15b9b 100644
--- a/lib/lib.mllib
+++ b/lib/lib.mllib
@@ -8,6 +8,7 @@ Segmenttree
 Unicodetable
 Unicode
 System
+CThread
 Spawn
 Spawned
 Trie
diff --git a/lib/spawned.ml b/lib/spawned.ml
index 29cf517690..9c304435b5 100644
--- a/lib/spawned.ml
+++ b/lib/spawned.ml
@@ -83,25 +83,3 @@ let get_channels () =
   | None -> Errors.anomaly(Pp.str "init_channels not called")
   | Some(ic, oc) -> ic, oc
 
-let prepare_in_channel_for_thread_friendly_blocking_input ic =
-  if Sys.os_type = "Win32" then Unix.set_nonblock (Unix.descr_of_in_channel ic)
-  else ()
-
-let thread_friendly_blocking_input ic =
-  if Sys.os_type = "Win32" then
-    let open Unix in
-    let open Thread in
-    let fd = descr_of_in_channel ic in
-    let rec loop buf n =
-      try read fd buf 0 n
-      with
-      | Unix.Unix_error((Unix.EWOULDBLOCK|Unix.EAGAIN),_,_) ->
-          (* We wait for some data explicitly yielding each second *)
-          while not (wait_timed_read fd 1.0) do yield () done;
-          loop buf n
-      | Unix.Unix_error _ -> 0
-    in 
-      loop
-  else
-    (fun buf n -> Pervasives.input ic buf 0 n)
-
diff --git a/lib/spawned.mli b/lib/spawned.mli
index bc5649a2fa..18b88dc64b 100644
--- a/lib/spawned.mli
+++ b/lib/spawned.mli
@@ -20,7 +20,3 @@ val init_channels : unit -> unit
 (* Once initialized, these are the channels to talk with our master *)
 val get_channels : unit -> in_channel * out_channel
 
-(* In multi threaded environments on windows blocking calls do
-   prevent context switch.  This seems a huge BUG, here a work around *)
-val prepare_in_channel_for_thread_friendly_blocking_input : in_channel -> unit
-val thread_friendly_blocking_input : in_channel -> string -> int -> int