Alexander A. Strelets created ZOOKEEPER-2891:
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Summary: SIGABRT from assert during fake completion on
zookeeper_close.
Key: ZOOKEEPER-2891
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2891
Project: ZooKeeper
Issue Type: Bug
Components: c client
Affects Versions: 3.4.10
Environment: Linux ubuntu 4.4.0-87-generic
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
https://github.com/apache/zookeeper.git
branch-3.4
Reporter: Alexander A. Strelets
Priority: Critical
Fix For: 3.4.10
Function *_deserialize_multi()_* hits *_assert(entry)_* when called for the so
called "Fake response" which is fabricated by the function _free_completions()_
for example when _zookeeper_close()_ is called while there is a pending _multi_
request.
Such fake response includes only the header but zero bytes for the body. Due to
this {{deserialize_MultiHeader(ia, "multiheader", &mhdr)}}, which is called
repeatedly for each {{completion_list_t *entry = dequeue_completion(clist)}},
does not assign the _mhdr_ and keeps _mhdr.done == 0_ as it was originally
initialized. Consequently the _while (!mhdr.done)_ does not ever end, and
finally falls into the _assert(entry)_ with _entry == NULL_ when all
sub-requests are "completed".
I propose to instruct the _deserialize_multi()_ function to break the loop on
_entry == NULL_ if it was called for an unsuccessfull overal status of the
multi response, and in particular for the fake response having _ZCLOSING_
(-116) status. I have introduced the _rc0_ parameter for this.
*Another issue* with this function is that even if the while-loop exited
properly, this function returns _rc == 0_, and this return code +overrides+ the
true status value with {{rc = deserialize_multi(xid, cptr, ia, rc)}} in the
_deserialize_response()_ function. So, the _multi_ response callback +handler
would be called with _rc == ZOK_ instead of _rc == ZCLOSING_+ which is strictly
wrong.
To fix this I propose initializing _rc_ with the introduced _rc0_ instead of
zero (which is _ZOK_ indeed).
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