Author: Armin Rigo <[email protected]>
Branch: extradoc
Changeset: r4934:381602717702
Date: 2012-12-08 18:32 +0100
http://bitbucket.org/pypy/extradoc/changeset/381602717702/
Log: Fix a subtle bug
diff --git a/talk/stm2012/stmimpl.rst b/talk/stm2012/stmimpl.rst
--- a/talk/stm2012/stmimpl.rst
+++ b/talk/stm2012/stmimpl.rst
@@ -233,7 +233,9 @@
if v > start_time: # object too recent?
if V >= LOCKED: # object actually locked?
goto retry # spin-loop to start of func
- ValidateDuringTransaction() # try to move start_time forward
+ start_time = GetGlobalCurTime() # copy from the global time
+ if not ValidateDuringTransaction():# try to move start_time forward
+ AbortTransaction()
goto retry # restart searching from R
PossiblyUpdateChain(G, R, ...) # see below
return R
@@ -454,22 +456,26 @@
until it gets unlocked, because it might turn out to point to a more
recent version that is still older than the current global time.
+We also have to talk over both the ``list_of_read_objects`` and the
+keys of ``global_to_local``: neither of these two lists is included
+in the other.
+
Here is ``ValidateDuringTransaction``::
def ValidateDuringTransaction():
- start_time = GetGlobalCurTime() # copy from the global time
- for R in list_of_read_objects:
+ for R in list_of_read_objects + global_to_local.keys():
v = R->h_revision
if not (v & 1): # "is a pointer", i.e.
- AbortTransaction() # "has a more recent revision"
+ return False # "has a more recent revision"
if v >= LOCKED: # locked
spin loop retry # jump back to the "v = ..." line
+ return True
The last detection for inconsistency is during commit, when
``ValidateDuringCommit`` is called. It is a slightly more complex
version than ``ValidateDuringTransaction`` because it has to handle
-"locks" correctly. It also returns a True/False result instead of
-aborting::
+"locks" correctly. It can also ignore ``global_to_local``, because they
+are handled differently during commit.
def ValidateDuringCommit():
for R in list_of_read_objects:
@@ -707,7 +713,7 @@
cur_time = global_cur_time # try again
if start_time != cur_time:
start_time = cur_time
- if not ValidateDuringCommit():
+ if not ValidateDuringTransaction():
global_cur_time = cur_time # must restore the value
inevitable_mutex.release()
AbortTransaction()
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