From c792d70ac7cccfcc0faf466ff23943b3808f4d6c Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Wed, 13 Sep 2017 18:39:14 +0200
Subject: [PATCH] assertions and cleanup in `CCPool`

---
 src/threads/CCPool.ml | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/threads/CCPool.ml b/src/threads/CCPool.ml
index 1863e2a8..914461cc 100644
--- a/src/threads/CCPool.ml
+++ b/src/threads/CCPool.ml
@@ -69,6 +69,8 @@ module Make(P : PARAM) = struct
 
   let incr_size_ p = p.cur_size <- p.cur_size + 1
   let decr_size_ p = p.cur_size <- p.cur_size - 1
+  let incr_idle_ p = p.cur_idle <- p.cur_idle + 1
+  let decr_idle_ p = p.cur_idle <- p.cur_idle - 1
 
   (* next thing a thread should do *)
   type command =
@@ -85,8 +87,7 @@ module Make(P : PARAM) = struct
       assert (pool.cur_size > 0);
       decr_size_ pool;
       Die
-    )
-    else if Queue.is_empty pool.jobs then Wait
+    ) else if Queue.is_empty pool.jobs then Wait
     else (
       let job = Queue.pop pool.jobs in
       Process job
@@ -94,6 +95,8 @@ module Make(P : PARAM) = struct
 
   (* Thread: entry point. They seek jobs in the queue *)
   let rec serve pool =
+    assert (pool.cur_size <= P.max_size);
+    assert (pool.cur_size > 0);
     let cmd = with_lock_ pool get_next_ in
     run_cmd cmd
 
@@ -101,7 +104,12 @@ module Make(P : PARAM) = struct
   and run_cmd = function
     | Die -> ()
     | Wait ->
-      with_lock_ pool (fun p -> Condition.wait p.cond p.mutex)
+      with_lock_ pool
+        (fun p ->
+           incr_idle_ pool;
+           Condition.wait p.cond p.mutex;
+           decr_idle_ pool);
+      serve pool
     | Process (Job1 (f, x)) ->
       begin try ignore (f x) with e -> pool.exn_handler e end; serve pool
     | Process (Job2 (f, x, y)) ->
@@ -116,6 +124,8 @@ module Make(P : PARAM) = struct
 
   (* launch the minimum required number of threads *)
   let () =
+    if P.min_size < 0 then invalid_arg "CCPool: min_size must be >= 0";
+    if P.min_size > P.max_size then invalid_arg "CCPool: min_size must be <= max_size";
     for _i = 1 to P.min_size do launch_worker_ pool done
 
   (* heuristic criterion for starting a new thread. *)
@@ -137,7 +147,7 @@ module Make(P : PARAM) = struct
          ) else (
            (* cannot start thread, push and wait for some worker to pick it up *)
            Queue.push job pool.jobs;
-           Condition.signal pool.cond; (* wake up *)
+           Condition.signal pool.cond; (* wake up some worker, if any *)
            (* might want to process in the background, if all threads are busy *)
            if pool.cur_idle = 0 && can_start_thread_ pool then (
              incr_size_ pool;
@@ -264,7 +274,7 @@ module Make(P : PARAM) = struct
           let l = List.rev_map (fun i ->
             Fut.make
               (fun () ->
-                Thread.delay 0.05;
+                Thread.delay 0.01;
                 1
             )) l in
           let l' = List.map Fut.get l in