.

wcfs/client/wcfs.cpp

@@ -248,11 +248,16 @@ error _Conn::__pin1(PinReq *req) {
     tie(f, ok) = wconn._filehtab.get_(req->foid);
     if (!ok) {
         wconn._filehmu.unlock();
-        return fmt::errorf("unexpected pin: file not watched"); // why wcfs sent us this update?
+        // why wcfs sent us this update?
+        return fmt::errorf("unexpected pin: f<%s> not watched", v(req->foid));
     }
 
-
     // XXX relock wconn -> f
+    // wconn.mu.unlock()
+    // f.mu.lock()
+    //
+    // XXX (?) NOTE: _not_ taking wconn.atMu at all (think more / explain why)
+    //         (e.g. deadlock with Conn.resync (wlocks atMu))
 
     for (auto mmap : f->_mmaps) {   // TODO use ↑blk_start for binary search
         if (!(mmap->blk_start <= req->blk && req->blk < mmap->blk_stop()))
@@ -429,11 +434,10 @@ pair<Mapping, error> _FileH::mmap(int64_t blk_start, int64_t blk_len, VMA *vma)
         panic("(blk_start + blk_len)*f.blksize overflow int64");
     int64_t start    = blk_start*f.blksize;
 
-    // XXX wconn.atMu.RLock()
-    // XXX defer wconn.atMu.RUnlock()
-
     // NOTE virtmem lock is held by virtmem caller
-    // XXX f locking?
+    // XXX locking
+    // XXX + wconn.atMu.RLock() ? -> y (e.g. f.headfsize is used)
+    // f.mu.lock()
 
     // create memory with head/f mapping and applied pins
     // mmap-in zeros after f.size (else access to memory after file.size will raise SIGBUS)
@@ -505,6 +509,7 @@ error _Mapping::unmap() {
 
     // NOTE virtmem lock is held by virtmem caller
     // XXX locking
+    // wconn.atMu.RLock() + f.mu.lock()
 
     if (mmap->vma != nil) {
         mmap->_assertVMAOk();
@@ -618,6 +623,7 @@ error _Mapping::_remmapblk(int64_t blk, zodb::Tid at) {
             v(f->wconn->_wc->mountpoint), v(f->wconn->at), v(f->foid), blk, v(at));
 
     // XXX locking done by callers (document)
+    // XXX cannot use wconn.at ^^^ because pinner does not lock wconn.atMu at all?
 
     ASSERT(mmap->blk_start <= blk && blk < mmap->blk_stop());
     error err;