test(writer-lock): hold the lock with a live child, not a pid assumed alive - #1753
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test(writer-lock): hold the lock with a live child, not a pid assumed alive#1753bompus wants to merge 1 commit into
bompus wants to merge 1 commit into
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… alive The live-holder case wrote `pid: 1` and leaned on its own comment, "On Linux, PID 1 is almost always alive". Windows has no PID 1, so tryAcquireWriterLock read the holder as dead and acquired — the correct behaviour for a dead holder, and a failing assertion. The platform-specific part was the fixture, not the lock. A parked child process is alive on every platform, and not stealing from a live holder is what the lock actually promises, so the case now tests the promise rather than a number that happens to name a running process. The child is reaped in afterEach. Fixes colbymchenry#1752.
This was referenced Sep 8, 2026
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Fixes #1752.
The problem
writer lock (#1740) > reports taken when a live foreign pid holds the lockfails on Windows, on a cleanmain, with nothing else present:The fixture writes
pid: 1as its live foreign holder and says so in its own comment — "On Linux, PID 1 is almost always alive." Windows has no PID 1, sotryAcquireWriterLockreads the holder as dead, clears the stale lock and acquires. That is the correct behaviour for a dead holder; the assertion is failing on the fixture, not on the lock.The change
Spawn a parked child and use its pid. It is alive on every platform, and "does not steal from a live holder" is what the lock actually promises — so the case now tests the promise rather than a number that happens to name a running process. On Linux it also stops depending on the ambient assumption about init. The child is killed in
afterEach.The sibling
clears a stale dead-pid lock and acquirescase still covers the dead-holder direction with2147483646, so both sides of the branch stay tested.Verification
__tests__/writer-lock.test.ts4/4 passbb204f8without the change: 1 failed / 3 passed, the case aboveI have not been able to run the Linux arm; the change is platform-neutral by construction, but worth a CI look.
Why I noticed
A downstream promotion pipeline gates on a zero-failure suite, so this single test blocked a Windows host from promoting any build of
main. Not urgent for the lock itself, which behaves correctly throughout.