.

wcfs/wcfs.go

@@ -420,6 +420,7 @@ package main
 // XXX describe locking
 //
 // head.zconnMu		write by handleδZ; read by read
+//			-> rlockZHead() + lockZHead() ?
 // ...
 
 // XXX locking: test with -race (many bugs are reported)
@@ -1438,8 +1439,8 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 	f := w.file
 
 	// register w to f here early, so that READs going in parallel to us
-	// preparing and processing initial pins, also send pins for read
-	// blocks. If we don't, we can miss to send pin for a freshly read
+	// preparing and processing initial pins, also send pins to w for read
+	// blocks. If we don't, we can miss to send pin to w for a freshly read
 	// block which could have revision > w.at:	XXX test
 	//
 	//                1   3    2   4
@@ -1456,7 +1457,7 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 	// pin for #3.
 	//
 	// NOTE for `unpin blk` head we can be sure there won't be simultaneous
-	// `pin blk` request, because:
+	// `pin blk` request, because:		XXX recheck
 	//
 	// - unpin means blk was previously pinned,
 	// - blk was pinned means it is tracked by δFtail,
@@ -1464,7 +1465,7 @@ func (wlink *WatchLink) setupWatch(ctx context.Context, foid zodb.Oid, at zodb.T
 	//   there is indeed no blk change in that region,
 	// - which means that δblk with rev > w.at might be only > head,
 	// - but such δblk are processed with zhead wlocked and we keep zhead
-	//   rlocked during pin setup. XXX rlock zhead
+	//   rlocked during pin setup.		XXX rlock zhead during setupWatch
 	//
 	//          δ                      δ
 	//      ----x----.------------]----x----

wcfs/wcfs_test.py

@@ -178,9 +178,7 @@ class tDB:
 
         # committed: (tail, head] + δF history
         t.tail   = t.root._p_jar.db().storage.lastTransaction()
-        t.head   = None # XXX -> property = dFtail[-1].rev ?
-        t._headv = []   # XXX -> just use dFtail[·].rev ?
-        t.dFtail = [] # of DF
+        t.dFtail = [] # of DF; head = dFtail[-1].rev
 
         # when ZBigFile(s) blocks were last accessed via wcfs.
         # this is updated only explicitly via ._blkaccess() .
@@ -194,6 +192,10 @@ class tDB:
         t._files    = set()
         t._wlinks   = set()
 
+    @property
+    def head(t):
+        return t.dFtail[-1].rev
+
     # close closes test database as well as all tracked files, watch links and wcfs.
     def close(t):
         for tf in t._files.copy():
@@ -253,8 +255,6 @@ class tDB:
 
         transaction.commit()
         head = last._p_serial
-        t.head = head
-        t._headv.append(head)
 
         print('\nM: commit -> %s' % t.hat(head))
         for zf, zfDelta in t._changed.items():
@@ -279,14 +279,14 @@ class tDB:
 
     # _wcsync makes sure wcfs is synchronized to latest committed transaction.
     def _wcsync(t):
-        while len(t._wc_zheadv) < len(t._headv):
+        while len(t._wc_zheadv) < len(t.dFtail):
             l = t._wc_zheadfh.readline()
             #print('> zhead read: %r' % l)
             l = l.rstrip('\n')
             wchead = fromhex(l)
             i = len(t._wc_zheadv)
-            if wchead != t._headv[i]:
-                raise RuntimeError("wcsync #%d: wczhead (%s) != zhead (%s)" % (i, h(wchead), h(t._headv[i])))
+            if wchead != t.dFtail[i].rev:
+                raise RuntimeError("wcsync #%d: wczhead (%s) != zhead (%s)" % (i, h(wchead), h(t.dFtail[i].rev)))
             t._wc_zheadv.append(wchead)
 
         # head/at = last txn of whole db
@@ -357,7 +357,7 @@ class tDB:
         if len(blkhistoryat) == 0:
             # blk did not existed @at       # XXX verify whether file was existing at all
             data = b''
-            rev  = t._headv[0]  # was hole - at0    XXX -> pin to z64
+            rev  = t.dFtail[0].rev  # was hole - at0    XXX -> pin to z64
         else:
             _ = blkhistoryat[-1]
             data = _.ddata[blk]
@@ -911,7 +911,7 @@ def _pinAt(t, zf, at):  # -> pin = {} blk -> rev
             # history of blk changes <= at
             blkhistoryat = [_.rev for _ in vdf if blk in _.ddata and _.rev <= at]
             if len(blkhistoryat) == 0:
-                pinrev = t._headv[0]    # was hole - at0  XXX -> pin to z64?
+                pinrev = t.dFtail[0].rev    # was hole - at0  XXX -> pin to z64?
             else:
                 pinrev = blkhistoryat[-1]
             assert pinrev <= at
@@ -1471,12 +1471,10 @@ def test_tidtime_notrough():
 #   @at2 (03cf7850500b5f66)
 @func(tDB)
 def hat(t, at):
-    try:
-        i = t._headv.index(at)
-    except ValueError:
-        return "@" + h(at)
-
+    for i, dF in enumerate(t.dFtail):
+        if dF.rev == at:
                 return "@at%d (%s)" % (i, h(at))
+    return "@" + h(at)
 
 
 # zfiles returns ZBigFiles that were ever changed under t.