Re: [PATCH] sched_ext/selftests: Fix bpf_link leak on assertion failure

Re: [PATCH] sched_ext/selftests: Fix bpf_link leak on assertion failure

[Tejun Heo]

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Hello,

In numa.c and rt_stall.c, the assertions check for SCX_EXIT_NONE — i.e.
the scheduler ran without error. bpf_link__destroy() triggers unregistration
which changes uei.kind to SCX_EXIT_UNREG, so moving it before the assertions
would make them always fail. Did you run the selftests after this patch?

A simpler approach would be using __attribute__((cleanup())) to auto-destroy
the link on any return path:

  static inline void autolink_destroy(struct bpf_link **linkp)
  {
  	if (*linkp)
  		bpf_link__destroy(*linkp);
  }

  #define __autolink __attribute__((cleanup(autolink_destroy)))

Then each test just does:

  struct bpf_link *link __autolink = bpf_map__attach_struct_ops(...);

No reordering needed — the link auto-destroys on any return, including
early returns from assertion failures.

Thanks.

--
tejun