The scaler is multi-threaded (monitor and demand threads); invoke() forked
and, in the child, logged, snprintf'd and setenv()'d before execl(), which
can deadlock on a lock another thread held at fork time and block the
caller in waitpid() forever.
run_script() now posix_spawn()s `sh <script> -f <in.json>`: stdout and
stderr go to the output file through file actions, the provider variables
(PRO_CONF_DIR, PRO_DATA_DIR, PRO_LOG_DIR, PROVIDER_NAME) are passed as the
child's envp (provider_env()), the child starts with an empty signal mask
and default dispositions, and waitpid() retries on EINTR.
The scaler unit suite (scaler/testsuite) was never built; it is now the
meson test "autoscaler test", linked with -Wl,--wrap=fork so it counts
fork() calls during a provider call.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Design constraint (tech.md "Process Creation"): the controller, scheduler,
xcecd and anything that starts libxce threads never call fork, vfork,
forkpty, daemon, system, popen or uv_spawn; children start with posix_spawn()
or a systemd unit. A process proven single-threaded may fork, marked
/* xce-fork-ok: <why> */. Tests, harness, autoscaler (not finalized; bug-1969)
and the Go frontend are out of scope.
- scripts/check-no-fork.py scans src/{controller,scheduler,lib,worker}
(comment/string/#if 0 aware); runs as meson test "no-fork rule" in the
lib/controller/scheduler/worker suites and in the pre-commit hook.
- worker: drop xcecd's unused fork-based worker start paths
(process_manager_start_process, process_manager_start_worker; xcecd
starts xcecd_worker over D-Bus) and a dead #if 0 daemonize fork.
- xcecd_worker's fork/uv_spawn/system calls are marked: its call graph
from main(), callbacks included, reaches no pthread_create or libuv
thread-pool call.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
