Linux

An industrial gateway (TI AM64x, Linux PREEMPT_RT) measured 30–60 ms Modbus-TCP RTT and 50–80 ms RTU jitter against a Windows simulator. After correcting the measurement semantics and running a three-step orthogonal isolation loopback (localhost → dual-NIC netns direct link → dual RS-485 crossover), the jitter is attributed to the test peer under these test conditions: board-side pure software stack 0.69 ms, physical NIC 1.02 ms, serial 4.15 ms (wire time about 70%); peer-side interventions such as the FTDI Latency Timer pinned the Windows bench’s measured lower bound at 45–50 ms, from which a reference timeout baseline is derived; a single gateway transaction consumes roughly 1%–15% of the end-to-end link budget — not a blocker.

How the first automated Linux release pipeline for Modbus-Tools (Qt 6 / C++) converged over multiple CI rounds. Six of the seven cross-platform failure classes share one pattern: “it ran elsewhere” is merely a localized surface phenomenon, not proof of correctness. From GNU ld member stripping and epoll/Winsock event ordering, through undefined behavior from two Qt socket engines fighting over one fd, to ELF RUNPATH contract splitting — building a deterministic release pipeline.

An industrial PC (TI AM64x heterogeneous SoC, A53 Linux + R5F RTOS, 24V supply) garbles continuously on a 3-wire RS-232 port at correct 115200 8N1 settings. Via SSH, the tx/rx/fe counters in /proc/tty/driver/serial verified both directions of the channel, ruling out software and unit defects; garbling persisted with only GND connected and vanished the moment the laptop’s power adapter was unplugged — a ground loop between the 24V industrial supply and mains. Dual-isolation converter verified in practice: no interference with the laptop plugged in.

A postmortem on a failed recovery path under Rootless Podman + Systemd user units, covering confirmed contributing factors, concrete remediation work, validation steps, and remaining risks.