#1188: STM.c:stmCommitNestedTransaction bogosity
-------------------------------+--------------------------------------------
Reporter: ms43 | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Runtime System | Version: 6.6
Severity: normal | Keywords:
Difficulty: Easy (1 hr) | Testcase:
Architecture: Multiple | Os: Multiple
-------------------------------+--------------------------------------------
there is a superfluous if (result) in stmCommitNestedTransaction in STM.c.
as a consequence, if check_read_only returns non-zero, revert_ownership
will not be called, which means that when the transaction is restarted and
reads a variable, that TVar will still be locked by the previous attempt,
resulting in an infinite loop in readTVar.
here is a patch (against ghc 6.6 darcs checked out on 2007-02-18).
{{{
--- /home/ms/www/ghc/rts/STM.c 2007-02-18 19:52:42.000000000 +0100
+++ ./STM.c 2007-03-02 23:27:53.000000000 +0100
@@ -1013,7 +1013,6 @@
// at the end of the call to validate_and_acquire_ownership. This
forms the
// linearization point of the commit.
- if (result) {
TRACE("%p : read-check succeeded\n", trec);
FOR_EACH_ENTRY(trec, e, {
// Merge each entry into the enclosing transaction record,
release all
@@ -1027,9 +1026,8 @@
merge_update_into(cap, et, s, e -> expected_value, e ->
new_value);
ACQ_ASSERT(s -> current_value != (StgClosure *)trec);
});
- } else {
+ } else {
revert_ownership(trec, FALSE);
- }
}
}
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1188>
GHC <http://www.haskell.org/ghc/>
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