Make log pipe test tolerate restricted kernels

[bneradt]

Some CI environments do not permit unprivileged processes to increase
FIFO buffer sizes, even when the requested size is below the system
maximum. The log_pipe AuTest treats this kernel policy as a product
failure and cannot run in those environments.

This makes the test accept only the corresponding Operation not permitted diagnostic when the FIFO remains unchanged, while continuing
to reject other errors and fatal diagnostics. It also waits briefly for
asynchronous diagnostic output before deciding whether the size check
failed.

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Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (2)

tests/gold_tests/logging/pipe_buffer_is_larger_than.py:61

• The diags log scan can raise a UnicodeDecodeError (or match an unrelated permission error) and incorrectly fail or pass the verifier. It’s safer to decode with replacement and to require that the permission error corresponds to the specific FIFO being checked.

        for _ in range(50):
            if os.path.exists(diags_log):
                with open(diags_log, encoding='utf-8') as diags:
                    diagnostics = diags.read()
                    if "Set pipe size failed" in diagnostics and "Operation not permitted" in diagnostics:
                        print("Success. The kernel denied increasing the pipe buffer for the unprivileged ATS user.")
                        return 0
            time.sleep(0.1)

tests/gold_tests/logging/log_pipe.test.py:136

• The negative-lookahead currently only permits the exact string immediately after "ERROR:". If the diags log includes timestamps/tags between "ERROR:" and the message, the allowed "Operation not permitted" line will still be treated as an unexpected error. Consider allowing arbitrary text after "ERROR:" before the permitted substring, and also re-adding the default "Unrecognized configuration value" exclusion since disable_log_checks disables it.

ts.Disk.diags_log.Content += Testers.ExcludesExpression(
    r"ERROR:(?! Set pipe size failed for pipe .*: Operation not permitted)", "The diagnostics should contain no unexpected errors.")
ts.Disk.diags_log.Content += Testers.ExcludesExpression("FATAL:", "The diagnostics should contain no fatal errors.")

[maskit]

Looks reasonable.

[cmcfarlen]

Cherry-picked to the 10.2.x branch as 9bafe09 for the 10.2.0 release.