From a3379065eaff2012d3b07e73dc4579b734b7ce3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gr=C3=A9goire=20Henry?= <gregoire.henry@tezos.com>
Date: Mon, 4 Mar 2019 19:12:39 +0100
Subject: [PATCH] Distributed_db: fix concurency issue on `Peer_validator`
 creation

---
 src/lib_shell/chain_validator.ml | 63 +++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 25 deletions(-)

diff --git a/src/lib_shell/chain_validator.ml b/src/lib_shell/chain_validator.ml
index c0508dd26..d97d67469 100644
--- a/src/lib_shell/chain_validator.ml
+++ b/src/lib_shell/chain_validator.ml
@@ -76,7 +76,7 @@ module Types = struct
     mutable child:
       (state * (unit -> unit Lwt.t (* shutdown *))) option ;
     mutable prevalidator: Prevalidator.t option ;
-    active_peers: Peer_validator.t P2p_peer.Table.t ;
+    active_peers: Peer_validator.t tzresult Lwt.t P2p_peer.Table.t ;
     bootstrapped_peers: unit P2p_peer.Table.t ;
   }
 
@@ -128,25 +128,26 @@ let may_toggle_bootstrapped_chain w =
 let may_activate_peer_validator w peer_id =
   let nv = Worker.state w in
   match P2p_peer.Table.find_opt nv.active_peers peer_id with
-  |Some pv -> return pv
-  |None ->
-      Peer_validator.create
-        ~notify_new_block:(notify_new_block w)
-        ~notify_bootstrapped: begin fun () ->
-          P2p_peer.Table.add nv.bootstrapped_peers peer_id () ;
-          may_toggle_bootstrapped_chain w
-        end
-        ~notify_termination: begin fun _pv ->
-          P2p_peer.Table.remove nv.active_peers peer_id ;
-          P2p_peer.Table.remove nv.bootstrapped_peers peer_id ;
-        end
-        nv.parameters.peer_validator_limits
-        nv.parameters.block_validator
-        nv.parameters.chain_db
-        peer_id
-      >>=? fun pv ->
+  | Some pv ->
+      pv
+  | None ->
+      let pv =
+        Peer_validator.create
+          ~notify_new_block:(notify_new_block w)
+          ~notify_bootstrapped: begin fun () ->
+            P2p_peer.Table.add nv.bootstrapped_peers peer_id () ;
+            may_toggle_bootstrapped_chain w
+          end
+          ~notify_termination: begin fun _pv ->
+            P2p_peer.Table.remove nv.active_peers peer_id ;
+            P2p_peer.Table.remove nv.bootstrapped_peers peer_id ;
+          end
+          nv.parameters.peer_validator_limits
+          nv.parameters.block_validator
+          nv.parameters.chain_db
+          peer_id in
       P2p_peer.Table.add nv.active_peers peer_id pv ;
-      return pv
+      pv
 
 let may_update_checkpoint chain_state new_head =
   State.Chain.checkpoint chain_state >>= fun (old_level, _old_block) ->
@@ -339,15 +340,22 @@ let on_completion (type a) w  (req : a Request.t) (update : a) request_status =
 let on_close w =
   let nv = Worker.state w in
   Distributed_db.deactivate nv.parameters.chain_db >>= fun () ->
+  begin
+    P2p_peer.Table.fold
+      (fun _ pv acc ->
+         acc >>= fun acc ->
+         pv >|= function
+         | Ok pv -> Peer_validator.shutdown pv :: acc
+         | Error _ -> acc)
+      nv.active_peers (Lwt.return [])
+  end >>= fun pvs ->
   Lwt.join
     (begin match nv.prevalidator with
        | Some prevalidator -> Prevalidator.shutdown prevalidator
        | None -> Lwt.return_unit
      end ::
      Lwt_utils.may ~f:(fun (_, shutdown) -> shutdown ()) nv.child ::
-     P2p_peer.Table.fold
-       (fun _ pv acc -> Peer_validator.shutdown pv :: acc)
-       nv.active_peers []) >>= fun () ->
+     pvs) >>= fun () ->
   Lwt.return_unit
 
 let on_launch start_prevalidator w _ parameters =
@@ -413,9 +421,14 @@ let on_launch start_prevalidator w _ parameters =
     end ;
     disconnection = begin fun peer_id ->
       Lwt.async begin fun () ->
-        may_activate_peer_validator w peer_id >>=? fun pv ->
-        Peer_validator.shutdown pv >>= fun () ->
-        return_unit
+        let nv = Worker.state w in
+        match P2p_peer.Table.find_opt nv.active_peers peer_id with
+        | Some pv ->
+            pv >>=? fun pv ->
+            Peer_validator.shutdown pv >>= fun () ->
+            return_unit
+        | None ->
+            return_unit
       end
     end ;
   } ;