.

wcfs/notes.txt

@@ -180,22 +180,22 @@ if we try to upload data to kernel pagecache from under serving read request,
 this can deadlock.
 
 Another case that needs to be cared about is interaction between uploadBlk and
-zwatcher: zconnMu being RWMutex, does not allow new RLocks to be taken once
+zwatcher: zheadMu being RWMutex, does not allow new RLocks to be taken once
 Lock request has been issued. Thus the following scenario is possible::
 
    uploadBlk      os.Read        zwatcher
 
                   page.Lock
-   zconnMu.Rlock
-                                 zconnMu.Lock
+   zheadMu.Rlock
+                                 zheadMu.Lock
    page.Lock
-                  zconnMu.Rlock
+                  zheadMu.Rlock
 
 
-- zwatcher is waiting for uploadBlk to release zconnMu;
+- zwatcher is waiting for uploadBlk to release zheadMu;
 - uploadBlk is waiting for os.Read to release page;
-- os.Read is waiting for zwatcher to release zconnMu;
+- os.Read is waiting for zwatcher to release zheadMu;
 - deadlock.
 
 To avoid such deadlocks zwatcher asks OS cache uploaders to pause while it is
-running, and retries taking zconnMu.Lock until all uploaders are indeed paused.
+running, and retries taking zheadMu.Lock until all uploaders are indeed paused.

wcfs/wcfs.go

@@ -310,8 +310,6 @@ package main
 //    4.6) processing ZODB invalidations and serving file reads (see 7) are
 //      organized to be mutually exclusive.
 //
-//	(TODO head.zheadMu -> special mutex with Lock(ctx) so that Lock could be canceled)
-//
 // 5) after OS file cache was invalidated, we resync zhead to new database
 //    view corresponding to tid.
 //
@@ -489,7 +487,7 @@ type Head struct {
 
 	// ZODB connection for everything under this head
 
-	// zheadMu protects access to zconn & live _objects_ associated with it.
+	// zheadMu protects zconn.At & live _objects_ associated with it.
 	// while it is rlocked zconn is guaranteed to stay viewing database at
 	// particular view.
 	//
@@ -665,6 +663,15 @@ func (_ *zodbCacheControl) PCacheClassify(obj zodb.IPersistent) zodb.PCachePolic
 	return 0
 }
 
+// -------- zhead lock/wait --------
+
+// TODO head.zheadMu -> special mutex with Lock(ctx) so that Lock wait could be canceled
+
+func (head *Head) zheadRLock()   { head.zheadMu.RLock() }
+func (head *Head) zheadRUnlock() { head.zheadMu.RUnlock() }
+func (head *Head) zheadLock()    { head.zheadMu.Lock() }
+func (head *Head) zheadUnlock()  { head.zheadMu.Unlock() }
+
 // -------- 4) ZODB invalidation -> OS cache --------
 
 func traceZWatch(format string, argv ...interface{}) {

wcfs/δftail.go

@@ -230,7 +230,7 @@ func (δFtail *ΔFtail) Update(δZ *zodb.EventCommit, zhead *ZConn) ΔF {
 
 		switch obj := obj.(type) {
 		case zBlk:	// ZBlk*
-			// z.infile locking: since we write-locked head.zconnMu
+			// z.infile locking: since we write-locked head.zheadMu
 			// - no other fuse reads are running, and thus no one
 			// is mutating z.infile. XXX recheck
 			z := obj.inΔFtail()