.

wcfs/internal/wcfs.h

@@ -102,7 +102,7 @@ typedef refptr<struct _Conn> Conn;
 struct _Conn : object {
     WCFS        *_wc;
     zodb::Tid   at;
-    WatchLink   _wlink; // watch/receive pins for created mappings
+    WatchLink   _wlink; // watch/receive pins for mappings created under this conn
 
     sync::Mutex             _filehmu;
     dict<zodb::Oid, FileH>  _filehtab; // {} foid -> fileh
@@ -131,8 +131,9 @@ private:
 
 // FileH represent isolated file view under Conn.
 //
-// The file view is maintained to be as of @Conn.at database state.
-// The file view uses /head/<file>/data primarilty and @revX/<file>/data pin overrides.
+// The file view is maintained to be as of @Conn.at database state even in the
+// presence of simultaneous database changes. The file view uses
+// /head/<file>/data primarily and @revX/<file>/data pin overrides.
 //
 // Use .mmap to map file view into memory.
 typedef refptr<struct _FileH> FileH;

wcfs/wcfs_test.py

@@ -1720,21 +1720,30 @@ class tMapping(object):
         dataok += b'\0'*(fh.blksize - len(dataok))   # trailing zeros
 
         blkview = t.mmap.mem[blk_inmmap*fh.blksize:][:fh.blksize]
-        # XXX first access without GIL, so that e.g. if there is timeout on
-        # wcfs.py side, _abort_ontimeout could run and kill WCFS.
-        # FIXME also test with GIL locked, since wcfs.py pinner must be itself
-        # running without GIL.  XXX
-        #_ = read_nogil(blkview[:1])
-        _ = blkview[0] # NOTE with gil
+        # NOTE access to memory goes _with_ GIL: this verifies that wcfs pinner
+        # is implemented in fully nogil mode because if that was not the case,
+        # the pinner would deadlock trying to acquire GIL in its thread while
+        # user thread that triggered the access is already holding the GIL.
+        #
+        #      - - - - - -
+        #     |           |
+        #        pinner <------.
+        #     |           |   wcfs
+        #        client -------^
+        #     |           |
+        #      - - - - - -
+        #     client process
+        #
+        _ = blkview[0]
         assert _ == dataok[0]
         assert blkview.tobytes() == dataok
 
     # XXX assertData
 
 
-# test_wcfspy_virtmem verifies wcfs.py integration with virtmem.
+# test_wcfs_virtmem unit-tests virtmem layer of wcfs client.
 @func
-def test_wcfspy_virtmem():
+def test_wcfs_virtmem():
     t = tDB(); zf = t.zfile
     defer(t.close)
 
@@ -1746,6 +1755,13 @@ def test_wcfspy_virtmem():
 
     fh = wconn.open(zf._p_oid)
     defer(fh.close)
+    # pinned(fh) returns fh.pinned with rev wrapped into tAt.
+    # XXX better wrap FileH into tFileH and do this automatically in .pinned ?
+    def pinned(fh):
+        p = fh.pinned.copy()
+        for blk in p:
+            p[blk] = tAt(t, p[blk])
+        return p
 
     # create mmap with 1 block beyond file size
     m1 = fh.mmap(2, 3)
@@ -1757,14 +1773,6 @@ def test_wcfspy_virtmem():
 
     tm1 = tMapping(m1)
 
-    # pinned returns fh.pinned with rev wrapped into tAt.
-    # XXX better wrap FileH into tFileH and do this automatically in .pinned ?
-    def pinned(fh):
-        p = fh.pinned.copy()
-        for blk in p:
-            p[blk] = tAt(t, p[blk])
-        return p
-
     #assertCache(m1, [0,0,0])
     assert pinned(fh) == {}