James Clampffer created HDFS-11436:
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Summary: libhdfs++: Fix race condition in ScopedResolver
Key: HDFS-11436
URL: https://issues.apache.org/jira/browse/HDFS-11436
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: James Clampffer
Assignee: James Clampffer
ScopedResolver holds a shared_ptr to a std::promise to do async stuff while the
calling thread blocks. The spec allows promise::set_value to unblock
future::wait immediately which causes future::get_value to race to read
whatever the promise contains before the state and value owned by the promise
is destroyed. In this case even though the ScopedResolver holds a shared_ptr
to the promise which looks like it'd prevent this but it's possible for wait to
unblock fast enough for the destructor on ScopedResolver to be called which
ends up destroying the promise. GCC's implementation tends of promises and
futures will hit this and will show up in valgrind as a bunch of invalid reads
if the timings are right to set up the race.
Simple fix right now is make sure the callback captures a shared_ptr to the
promise. Longer term fix may be to make a class that encapsulates the promise
and future with a reference counting mechanism to prevent more of these bugs
and use that instead of the std lib versions.
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