.

wcfs/client/wcfs.cpp

@@ -486,7 +486,7 @@ error _Conn::resync(zodb::Tid at) {
     //
     // NOTE we'll relock atMu as R in the second part of resync, so we prelock
     // wconn._filehMu.R as well while under atMu.W, to be sure that set of opened
-    // files stays the same during whole resync.
+    // files and their states stay the same during whole resync.
     bool atMuWLocked = true;
     wconn._atMu.Lock();
     wconn._filehMu.RLock();
@@ -529,7 +529,10 @@ error _Conn::resync(zodb::Tid at) {
         // TODO if file has no mappings and was not used during whole prev
         // cycle - forget and stop watching it
 
-        // XXX not yet ready f
+        // opening or closing fileh, whose setup/teardown is handled by
+        // Conn.open and FileH.close correspondingly.
+        if (f._state != _FileHOpened)
+            continue;
 
         // update f._headfsize and remmap to head/f zero regions that are now covered by head/f
         struct stat st;
@@ -569,7 +572,8 @@ error _Conn::resync(zodb::Tid at) {
     // - we need to hold atMu.R to avoid race wrt e.g. other resync which changes at.
     // - we cannot just do regular `atMu.Unlock + atMu.RLock()` because then
     //   there is e.g. a race window in between Unlock and RLock where wconn.at can be changed.
-    //   XXX also deadlock, because it will become wconn._filehMu.lock + wconn._atMu lock
+    //   Also if we Unlock and Rlock, it will produce deadlock, because locking
+    //   order will change to reverse: wconn._filehMu.R + wconn._atMu.R
     //
     // Now other calls, e.g. Conn.open, can be running simultaneously to us,
     // but since we already set wconn.at to new value it is ok. For example
@@ -663,7 +667,7 @@ retry:
         return make_pair(f, nil);
     }
 
-    // create "opening" FileH entry and perform open with wconn._filehMu released
+    // create "opening" FileH entry and perform open with wconn._filehMu released.
     // NOTE wconn._atMu.R is still held because FileH._open relies on wconn.at being stable.
     f = adoptref(new _FileH());
     f->wconn      = newref(&wconn);

wcfs/client/wcfs.h

@@ -231,7 +231,7 @@ struct _FileH : object {
     Conn        wconn;
     zodb::Oid   foid;       // ZBigFile root object ID (does not change after fileh open)
 
-    // protect by wconn.filehMu
+    // protect by wconn._filehMu
     _FileHState _state;  // opening/opened/closing/closed
     int         _nopen;  // number of times Conn.open returned this fileh