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pybind/rados: fix object lifetime issues and other bugs in aio #7778

Merged
merged 2 commits into from Mar 1, 2016
Merged

pybind/rados: fix object lifetime issues and other bugs in aio #7778

merged 2 commits into from Mar 1, 2016

Commits on Feb 24, 2016

  1. pybind/rados: Fix error handling and leaks in aio 

    aio_read:
The reference to ret_s begins existing at PyBytes_FromStringAndSize and
is handed over to the callback if rados_aio_read succeeds. This creates
a lot of subtle scenarios where it might not be XDECREFed (e.g. if
a KeyboardInterrupt arrives at the wrong time). Instead, store the pointer
to that buffer in the completion object, and hand over responsibility for
the XDECREF to it. This guarantees that the "special" reference to this
incomplete object will be released when the completion object is
deallocated.

Also make sure we don't try to _PyBytes_Resize with a negative length.

Add a failure case to the aio_read test in test_rados.py

Completion: the wrapper methods weren't being called, which prevents
the completion objects from being freed until the Ioctx is. Fix this
and add a refcount check to the aio_read test.

Signed-off-by: Hector Martin <marcan@marcan.st>
    @marcan
    marcan committed Feb 24, 2016
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  2. pybind/rados: track completions before calling aio functions 

    Tracking completions is critical for memory safety - if the
aio function succeeds, the completion must be tracked. However,
if a KeyboardInterrupt or similar arrives between the call and
the tracking, the completion will not be tracked.

Fix this by tracking the completion before the aio call, and
explicitly cleaning up in the failure case.

This leaves the opposite problem, where an unexpected exception
(other than simple error return from the aio function) will cause
the completion to not be freed until the Ioctx is destroyed, but
that is a relatively minor issue.

Signed-off-by: Hector Martin <marcan@marcan.st>
    @marcan
    marcan committed Feb 24, 2016
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