[release/6.0] Make sure EventPipe streaming thread won't write session->streaming_thread after session free. #58710
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…hread after session free. In case where ep_disable is called by a different thread (close IPC command) there was a race between streaming threads setting session->streaming_thread to NULL and IPC command triggering a call to disable_holding_lock and freeing session. Resetting the streaming_thread in streaming thread must happens before it signals its shutdown event to prevent the race.
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jeffschwMSFT
approved these changes
Sep 7, 2021
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It looks like all the CI failures were Helix/Infrastructure related. I think a re-run should ameliorate them. |
josalem
approved these changes
Sep 7, 2021
ghost
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Backport of #58615 to release/6.0
/cc @lateralusX
Customer Impact
Race condition writing to memory after free causing rare, but hard to diagnose runtime AV's. Only reproduced on CI so far only seen on CoreCLR, but could happen on all platforms, including platforms handled by MonoVM. Crash described in several issues like #57461.
Testing
Have been hit on CI multiple times over the last 3 week's, so we should have CI test cases the runs this code path very frequently (since the window for this race condition is small).
Risk
Low, we have many CI tests cover this code path and resetting the memory area to NULL is currently done to preventing future issues if we add logic acting on this field (like restart streaming on existing session using a different streaming thread), so no code currently depends on the value written into the field and therefore not affected.