logan
49445ded77
The kernel refuses to exec a file that is open for writing anywhere in the process, and these tests are parallel: a sibling's fork duplicates stubYtDlp's write descriptor in the moment it is open and carries it past our close, so the exec a moment later fails with ETXTBSY. That is the flake seen once locally and once in CI, both times on a tree with no Go in its diff. Closing sooner is not available -- os.WriteFile has already closed the file before anything execs it -- and O_CLOEXEC does not help, because the window is between another goroutine's fork and its own exec. syscall.ForkLock is the lock forkExec takes across that fork, so holding it over the write means no child can exist while the descriptor does. Measured on the helper itself under 12 concurrent writers: 176-189 of 2400 execs refused before, 0 of 2400 after, three runs each. Closes #146