kqueue: drop watches directly in Close() instead of going through remove()#740
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…ove() Close() called w.Remove(name) in a loop after w.shared.close() marked the watcher closed, but w.Remove -> w.remove short-circuits on w.isClosed() and returns nil without calling unix.Close on the watch fd or touching the watches bookkeeping. Every directory (and each file inside it - a dir watch opens one fd per child on macOS) leaked its descriptor on Close, so long-running processes that recycle watchers (hot-reload dev servers, test harnesses) hit EMFILE after a few cycles (fsnotify#732). Iterate the paths directly in Close(): register the EV_DELETE kevent, unix.Close the fd, and drop the watches entry. The pre-existing kqueue.remove() path is unchanged, so Remove() on a live watcher keeps the same semantics; only Close() stops leaning on it. Adds TestCloseClearsWatchState: creates a watcher over a dir + file, calls Close, and asserts every watches map is drained. Fails on master (3 path entries, 3 wd entries, 2 byUser, 3 byDir remain) and passes with the fix. Fixes fsnotify#732 Signed-off-by: SAY-5 <SAY-5@users.noreply.github.com>
mattn
reviewed
Apr 22, 2026
| for _, name := range pathsToRemove { | ||
| w.Remove(name) | ||
| info, ok := w.watches.byPath(name) | ||
| if !ok { |
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if !ok {
w.watches.remove(0, name)
continue
}
mattn
suggested changes
Apr 22, 2026
Per @mattn's review on fsnotify#740: if the Close loop walks a name from w.path but byPath can't resolve it to a live w.wd entry, the w.path / w.byUser entries for that name are still live and would survive Close. Call w.watches.remove(0, name) on the not-ok branch so the lookup maps are left consistent even in that inconsistent-state corner case.
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Thanks @mattn — applied your suggestion. The not-ok branch now calls |
mattn
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Apr 22, 2026
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I'll look this in later again. Thank you
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Thank you |
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Summary
Fixes #732.
kqueue.Close()callsw.Remove(name)in a loop afterw.shared.close()has marked the watcher closed.w.Removeroutes throughw.remove, which short-circuits onw.isClosed()and returns nil without callingunix.Closeon the watch fd or dropping the watches bookkeeping. Every directory watch (and each file inside it — a dir watch opens one fd per child on macOS) leaked its descriptor onClose, so long-running processes that recycle watchers (hot-reload dev servers, test harnesses) hitEMFILEafter a few cycles.Fix
Iterate the paths directly in
Close(): register theEV_DELETEkevent,unix.Closethe fd, and drop thewatchesentry.kqueue.remove()is unchanged, soRemove()on a live watcher keeps the same semantics; onlyClose()stops leaning on it.Tests
Adds
TestCloseClearsWatchStateinbackend_kqueue_test.go: creates a watcher over a temp dir + file, callsClose, and asserts everywatchesmap is drained.watches.path: 3 entries,watches.wd: 3 entries,watches.byUser: 2 entries,watches.byDir: 3 entries.go test -count=1 ./...green on darwin;go vetclean.