.

wcfs/client/wcfs.cpp

@@ -149,7 +149,6 @@ error _Conn::close() {
     if (!errors::Is(err, context::canceled)) // canceled - ok
         reterr1(err);
 
-
     // pinner is stopped - now close all files - both that have no mappings and
     // that still have opened mappings.
     //
@@ -194,9 +193,9 @@ error _Conn::_pinner(context::Context ctx) {
     }
 
     // mark the connection non-operational if the pinner fails
-    wconn._mu.lock();   // XXX locking ok? -> merge into below where lock is held? XXX + atMu.R ?
+    wconn._mu.lock();   // XXX locking ok? -> merge into below where lock is held?
     if (wconn._downErr == nil) {
-        wconn._downErr = fmt::errorf("no longer operational due to: %w", err);
+        wconn._downErr = fmt::errorf("no longer operational due to: %w", err);  // XXX err=nil ?
         // XXX make all fileh and mapping invalid.
     }
     wconn._mu.unlock();
@@ -335,10 +334,13 @@ error _Conn::__pin1(PinReq *req) {
 pair<FileH, error> _Conn::open(zodb::Oid foid) {
     _Conn& wconn = *this;
     error err;
-    xerr::Contextf E("%s: open f<%s>", v(wconn), v(foid));
 
-    // XXX wconn._atMu.RLock()
-    // XXX defer wconn._atMu.RUnlock()
+    wconn._atMu.RLock();
+    defer([&]() {
+        wconn._atMu.RUnlock();
+    });
+
+    xerr::Contextf E("%s: open f<%s>", v(wconn), v(foid));
 
     wconn._mu.lock();
 
@@ -361,6 +363,7 @@ pair<FileH, error> _Conn::open(zodb::Oid foid) {
     }
 
     // create in-flight-opening FileH entry and perform open with wconn._mu released
+    // NOTE wconn._atMu is still held because open relies on wconn.at being stable.
     f = adoptref(new _FileH());
     f->wconn      = newref(&wconn);
     f->foid       = foid;
@@ -388,6 +391,11 @@ pair<FileH, error> _Conn::open(zodb::Oid foid) {
 }
 
 // _open performs actual open of FileH marked as "in-flight-open" in wconn.filehTab.
+//
+// Called with:
+// - wconn.atMu held
+// - wconn.mu   not locked
+// - f.mu       not locked
 error _FileH::_open() {
     _FileH* f = this;
     Conn    wconn = f->wconn;
@@ -415,7 +423,7 @@ error _FileH::_open() {
                         v(f->_headf->name()), f->_headfsize, f->blksize);
 
     // start watching f
-    // NOTE we are _not_ holding wconn.mu nor f.mu  XXX wconn.atMu?
+    // NOTE we are _not_ holding wconn.mu nor f.mu - only wconn.atMu to rely on wconn.at being stable.
     string ack;
     tie(ack, err) = wconn->_wlink->sendReq(context::background(), fmt::sprintf("watch %s @%s", v(foid), v(wconn->at)));
     if (err != nil)