test-worker: capture tracebacks more reliably The traceback test may have traceback caused by SIGTERM. Instead of grepping "Traceback", explicitly grep the exception we care about. This makes the test less flaky.

worker: rewrite error handling so os._exit covers all cases Previously the worker error handling is like: pid = os.fork() --+ if pid == 0: | .... | problematic .... --+ try: --+ .... | worker error handling --+ If a signal arrives when Python is executing the "problematic" lines, an external error handling (dispatch.py) will take over the control flow and it's no longer guaranteed "os._exit" is called (see 86cd09bc13ba for why it is necessary). This patch rewrites the error handling so it covers all possible code paths for a worker even during fork. Note: "os.getpid() == parentpid" is used to test if the process is parent or not intentionally, instead of checking "pid", because "pid = os.fork()" may be not atomic - it's possible that that a signal hits the worker before the assignment completes [1]. The newly added test replaces "os.fork" to exercise that extreme case. [1]: CPython compiles "pid = os.fork()" to 2 byte codes: "CALL_FUNCTION" and "STORE_FAST", so it's probably not atomic: def f(): pid = os.fork() dis.dis(f) 2 0 LOAD_GLOBAL 0 (os) 3 LOAD_ATTR 1 (fork) 6 CALL_FUNCTION 0 9 STORE_FAST 0 (pid) 12 LOAD_CONST 0 (None) 15 RETURN_VALUE

dispatch: take over SignalInterrupt handling from scmutil dispatch handles KeyboardInterrupt already. This makes the code more consistent, and makes worker not print "killed!" if it receives SIGTERM in most cases (in rare cases there is still "killed!" printed, which will be fixed by the next patch).