Definition
Plain language
A Unix signal that instantly freezes a running program in place, so it can be woken up again later exactly as it was.
As stated in the literature
The POSIX signal that unconditionally suspends a process's execution; used in DeltaCR to freeze a forked parent process as a fast-restore checkpoint template.
Also called: stop signal
Why it matters: It lets a system snapshot a process in place for fast restoration, providing a cheap way to checkpoint and revive work.
For example, sending SIGSTOP to a running program freezes it mid-task like hitting pause, so it can be resumed later exactly where it left off.
Heard on the show
“The parent gets immediately frozen with a stop signal.”Episode 068 — The OS Trick That Makes Tree Search Practical for Coding Agents