[release/6.0] Fix memory leak in enqueue/dequeue of EventPipe callback data. #58244
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#56104 made sure provider callback data gets its own copy of filter data. This created a couple of memory leaks when queue/dequeue the callback data since callback data was not correctly freed in these scenarios leading to leaks of the copied filter data. Was detected running the manual EventPipe native unit tests on Windows using its build in use of _CrtMemCheckpoint (only available in debug builds) automatically detecting memory leaks. Fix makes sure callback data is moved into queue on enqueue and moved out in dequeue and that caller of dequeue make sure to free returned callback data using ep_provider_callback_data_fini when done using it. Doing a move instead of copy will also reduce the number of allocations when enqueue/dequeue callback data in provider callback queue.
marek-safar
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marek-safar
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Aug 27, 2021
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//CC @josalem, backport to net6. |
josalem
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Aug 27, 2021
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Backport of #58170 to release/6.0
/cc @lateralusX
Customer Impact
Small memory leak on each EventSource EventPipe provider enable/disable callback invocation introduced by #56104. Leak size is size of callback filter_data on enable and disable. Filter data is not used in all scenarios and for cases where filter data is not used nothing will be leaked. NOTE, memory leak affects both CoreCLR as well as Mono.
Testing
We have native EventPipe tests that can be run with automatic memory leak detection in debug build. It is currently not automated, so needs to be run manually (that's how this memory leak was found), https://github.com/dotnet/runtime/tree/main/src/mono/mono/eventpipe/test.
Risk
Low. Since the leak is small it can be discussed if we should leave it as is. Filter data can however be passed over our diagnostic IPC protocol when starting a session, so it is possible to trigger this memory leak over IPC.