Matt-Esch opened a new pull request, #15508:
URL: https://github.com/apache/pulsar/pull/15508
### Motivation
The pulsar-client-node library uses the c api to interact with the pulsar
client. The model for the c api is to pass in a `void *ctx` to async functions
with a callback. Typically, these callbacks free the context and rely heavily
on the fact that the callback is called once. I was able to reproducibly
trigger the close callback to call twice, resulting in a double free error in
pulsar-client-node.
### Modifications
My running theory is that the cause for this is a race condition in the
decrementing of `numberOfOpenHandlers` shared pointer. It is possible for two
threads to decrement the number in parallel, and to both end up with
`*numberOfOpenHandlers == 0`. This fix assumes this can happen and synchronizes
on the state, so even if this does happen, only one thread will be able to set
the state to `Closed` and create the subsequent shutdown task.
### Verifying this change
- [ ] Make sure that the change passes the CI checks.
- [ ] Run reproduction steps with pulsar-client-node using the new version
This change is already covered by existing tests, such as all of the tests
in ClientTest.cc. Given that this is a race condition it's not possible to
reproduce consistently for tests. I will run reproduction steps with
pulsar-client-node.
### Does this pull request potentially affect one of the following parts:
- Dependencies (does it add or upgrade a dependency): no
- The public API: no
- The schema: no
- The default values of configurations: no
- The wire protocol: no
- The rest endpoints: no
- The admin cli options: no
- Anything that affects deployment: no
### Documentation
- [ ] `doc-required`
- [x] `no-need-doc`
- [ ] `doc`
- [ ] `doc-added`
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