fix(exec): detach child stdin to /dev/null so commits don't hang on a serial console#118
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…'t block on a serial console Exec() redirects the child's stdout/stderr but leaves stdin inherited from the parent (hex_config). On a serial-console install (IPMI Serial-over-LAN, /dev/ttyS0) the commit subprocesses inherit that UART as stdin. Tools that initialize a terminal on stdin -- e.g. mongosh during the mongodb module commit -- then block forever opening the controlling TTY in tty_port_block_til_ready (waiting for carrier; CLOCAL unset), stalling the entire policy apply at the mongodb stage. Commit subprocesses never read stdin, so redirect it to /dev/null, mirroring the existing stdout/stderr /dev/null handling. This makes commits independent of the console type (serial/SOL vs VGA). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Signed-off-by: Travis Wu <travis.wu@bigstack.co>
Add test_exec_stdin_01, which gives the parent process a non-/dev/null stdin and asserts an Exec()-spawned child still sees /dev/null -- guarding the serial-console hang fix. Wire a tests/ dir into the SDK library Makefile, since exec.cpp is compiled directly at the SDK root. Also condense the inline comment on the stdin redirect. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Signed-off-by: Travis Wu <travis.wu@bigstack.co>
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leechienpang
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Jun 29, 2026
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What type of PR is this?
/kind bug
What this PR does / why we need it
On a serial-console install (IPMI Serial-over-LAN,
/dev/ttyS0),hex_config's commit subprocesses inherit the UART as stdin.Exec()redirected the child's stdout/stderr but left stdin inherited from the parent. Tools that initialize a terminal on stdin — e.g.mongoshduring the mongodb module commit — then block forever opening the controlling TTY intty_port_block_til_ready(waiting for carrier;CLOCALunset), stalling the entire policy apply at the mongodb stage. VGA/console installs are unaffected because their stdin is not a blocking UART.Commit subprocesses never read stdin, so this redirects the child's stdin to
/dev/nullinExec(), mirroring the existing stdout/stderr/dev/nullhandling. Commits become independent of console type (serial/SoL vs VGA).Which issue(s) this PR fixes
Fixes bigstack-oss/cubecos#1016 (the cubecos tracking issue; cubecos picks up this fix via a hex submodule bump).
Special notes for your reviewer
Adds
test_exec_stdin_01: gives the parent process a non-/dev/nullstdin (/dev/zero) and asserts that anExec()-spawned child still sees/dev/null. Confirmed it fails without the fix (child inherits/dev/zero) and passes with it. Fullhex_sdk_librarymake testis green (128/128) in the centos9 jail.Also verified end-to-end downstream: a full serial-console (SoL) CubeCOS install on a build carrying this fix completes all 22 bootstrap stages — the mongodb stage no longer hangs.
Additional documentation
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