Fix several issues uncovered while investigating recent CI failures #155

These variables are unused, as `ProcessManager.create_from_pid` now parses the maps file itself; the caller doesn't need to. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

Previously we were pausing the process only after we had already fetched the processes mappings, leading to a potential TOCTOU issue: the fetched mappings might be stale by the time the process was paused and we were ready to use them. Handle this by creating a new `ProcessTracer` class responsible for pausing the process. This class matches the behavior that was previously found in `BlockingProcessMemoryManager`, except that it's not also an instance of `AbstractRemoteMemoryManager`: it handles only tracing the process on construction, and detaching on destruction. In blocking mode, we create a `ProcessTracer` before reading the mappings. Later, we pass it to the `ProcessManager`, which takes over ownership of it, destroying it when we're done analyzing the process and want to detach. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

By having the tracer expose the list of thread IDs that it stopped, the manager can avoid a call to find the list of thread IDs itself. Since every thread must be paused when there is a tracer, the tracer's list of threads must be accurate. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

Previously, we were fetching the process's list of threads once, and iterating over that list attaching to each thread. This is racy, though: after we get the list of threads and before we've suspended every thread, it's still possible for new threads to start or old threads to finish. Handle this by fetching the list of threads at least twice. When we encounter an error trying to attach to a thread, don't report it unless the next call to list all of the threads says that thread still belongs to the process we're attaching to (if the thread has disappeared from the list, then the reason we failed to attach to that thread is that it has died). Similarly, if any new threads show up in the second list of threads, we'll try to pause those, repeating this until the set of threads that we've paused contains every thread that the process currently owns. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

This is called from C++ code that doesn't know how to propagate a Python exception if one should occur. Tell Cython not to allow an exception to escape from this function, and to instead print and discard one if it should occur. Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

Leverage our existing `_try_to_decode_string` function which uses `errors="replace"` for decoding, guaranteeing that log messages won't be lost entirely if they contain non-UTF-8 data. Also, pass the log message around as a C++ string rather than a C string, which is more efficient anyway (since the size is known and doesn't need to be computed). Signed-off-by: Matt Wozniski <mwozniski@bloomberg.net>

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Fix several issues uncovered while investigating recent CI failures #155

Fix several issues uncovered while investigating recent CI failures #155

Commits on Nov 17, 2023