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fix: give back the thread ports a CPU sample is handed - #25
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task_threads returns a port for every thread along with the list, and only the list was released. Each port kept outlived its thread as a dead name, so an observed Performance panel, sampling once a second, left one behind in the app for every thread it ever ran.
heoblitz
approved these changes
Oct 15, 2026
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Summary
task_threadsreturns a send right for every thread along with the list, and the CPU sampler inNectoProcessMetricsreleased only the list (vm_deallocate). Each port it kept outlives its thread as a dead name, so while the Performance panel is observing — one sample a second — the app it runs in accumulates one Mach port name for every thread it ever ran. Each port is nowmach_port_deallocated before the list is freed.Changelog
Fix the Performance plugin leaking a Mach port per sampled thread in the connected app.
Test Plan
swift test: 161 tests in 11 suites passed. The new testreleasesThreadPortsparks a short-lived thread, takes aperformance.snapshot, ends the thread, 300 times over, and comparesmach_port_namescounts: onmainit leaks 301 names; with the fix the delta stays under the 100 allowed for noise.