| commit | 44a1f7e7cabebff853ccfbbb669f79673a2ec335 | [log] [tgz] |
|---|---|---|
| author | David Peixotto <peix@meta.com> | Thu Sep 18 08:20:09 2025 -0700 |
| committer | GitHub <noreply@github.com> | Thu Sep 18 08:20:09 2025 -0700 |
| tree | 53dca7e6fc24ced5995336a6eb170ce329a8d3af | |
| parent | 6e47bff24d83ea4db74cf548146baf6170aeb9f0 [diff] |
[lldb] Fix unsafe map mutation in ProcessElfCore::FindModuleUUID (#159444)
The `ProcessElfCore::FindModuleUUID` function can be called by multiple
threads at the same time when `target.parallel-module-load` is true. We
were using the `operator[]` to lookup the UUID which will mutate the map
when the key is not present. This is unsafe in a multi-threaded contex
so we now use a read-only `find` operation and explicitly return an
invalid UUID when the key is not present.
The `m_uuids` map can follow a create-then-query pattern. It is
populated in the `DoLoadCore` function which looks like it is only
called in a single-threaded context so we do not need extra locking as
long as we keep the other accesses read-only.
Other fixes I considered
* Use a lock to protect access - We don't need to modify the map after
creation so we can allow concurrent read-only access.
* Store the map in a const pointer container to prevent accidental
mutation in other places.
- Only accessed in one place currently so just added a comment.
* Store the UUID in the NT_FILE_Entry after building the mapping
correctly in `UpdateBuildIdForNTFileEntries`. - The map lets us avoid a
linear search in `FindModuleUUID`.
This commit also reverts the temporary workaround from #159395 which
disabled parallel module loading to avoid the test failure.
Fixes #159377
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