Re: [PATCH v8] perf record: Fix unhandled POLLHUP on non_perf_event descriptors

On Thu, Aug 20, 2026 at 2:47 PM <[email protected]> wrote:
>
> > When processing POLLHUP on a non_perf_event control descriptor,
> > evlist__finalize_ctlfd() is invoked to finalize the setup, correctly
> > setting the core evlist's poll array file descriptor to -1. However,
> > this finalized teardown state is never propagated back to the
> > individual thread's local replica of the pollfd array.
> >
> > Consequently, on the next iteration of the main recording loop,
> > record__update_evlist_pollfd_from_thread() performs a strict
> > equivalence check between the core evlist's array and the thread's
> > localized poll array, detecting that the fd values no longer match.
> > This causes an immediate -EINVAL abort and a premature teardown.
> >
> > Fix the underlying logic within
> > record__update_evlist_pollfd_from_thread() to sustainably propagate
> > the finalized teardown statuses (-1) originating from the core evlist
> > back to the thread's localized poll structure. This correctly
> > maintains synchronization and entirely prevents the unhandled
> > index mismatch crashes.
> >
> > Additionally, add a unit test that explicitly validates that
> > fdarray__filter() preserves its invariants regarding
> > fdarray_flag__nonfilterable items to guard against regressions.
> >
> > Fixes: fb4751e79c45 ("perf record: Fix teardown hang on system-wide multi-threaded sessions")
> > Assisted-by: Gemini:gemini-3.1-pro
> > Signed-off-by: Ian Rogers <[email protected]>
>
> Sashiko has reviewed this patch and found no issues. It looks great!

Random unnecessary comment: v6, v7 and v8 only differ by comments. The
comments were added to avoid hallucinations in the issues Sashiko was
seeing; I wasn't seeing the issue internally. This is the first time
I've encountered this problem.

Thanks,
Ian

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>