.

wcfs/client/wcfs.cpp

@@ -385,22 +385,29 @@ error _Conn::__pin1(PinReq *req) {
         wconn._atMu.RUnlock();
     });
 
+    // lock wconn.filehMu.R to lookup fileh in wconn.filehTab.
+    // keep wconn.filehMu.R during whole __pin1 to make sure that e.g.
+    // simultaneous close does not remove f from wconn.filehTab.
+    // TODO keeping filehMu.R during whole pin is not needed and locking can be made more granular.
+    //
     // NOTE no deadlock wrt Conn.resync, Conn.open, FileH.close - they all send
     // "watch" outside of wconn.filehMu.
     wconn._filehMu.RLock();
-    // XXX +incref f, so that simultaneous close does not remove f from wconn.filehTab ?
-    // XXX or just make FileH.close lock f too to synchronize with pinner?
-    // XXX or just keep wconn._filehMu.R during whole __pin1()
+    defer([&]() {
+        wconn._filehMu.RUnlock();
+    });
+
     tie(f, ok) = wconn._filehTab.get_(req->foid);
     if (!ok) {
-        wconn._filehMu.RUnlock();
         // why wcfs sent us this update?
         return fmt::errorf("unexpected pin: f<%s> not watched", v(req->foid));
     }
 
-    // XXX <- f._openReady ?
+    // NOTE no need to check f._state as we need to go only through f.mmaps, and
+    // wcfs server can send us pins at any state, including "opening" - to pin
+    // our view to requested @at, and "closing" - due to other clients
+    // accessing wcfs/head/f simultaneously.
 
-    wconn._filehMu.RUnlock(); // XXX maybe `f.mu.lock() -> wconn.filehMu.unlock()` to avoid race with FileH close?
     f->_mu.lock();
     defer([&]() {
         f->_mu.unlock();
@@ -447,7 +454,7 @@ error _Conn::__pin1(PinReq *req) {
         if (err != nil)
             return err;
 
-        //trace("\t-> remmaped");   XXX
+        //trace("\t-> remmaped");
     }
 
     // update f._pinned