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Miller" Cc: netdev@vger.kernel.org, linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Kconfig, DEFAULT_NETSCH, and shooting yourself in the foot.. Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1609618487_2273P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Sat, 02 Jan 2021 15:14:47 -0500 Message-ID: <16871.1609618487@turing-police> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org --==_Exmh_1609618487_2273P Content-Type: text/plain; charset=us-ascii Consider the following own goal I just discovered I scored: [~] zgrep -i fq_codel /proc/config.gz CONFIG_NET_SCH_FQ_CODEL=m CONFIG_DEFAULT_FQ_CODEL=y CONFIG_DEFAULT_NET_SCH="fq_codel" Obviously, fq_codel didn't get set as the default, because that happens before the module gets loaded (which may never happen if the sysadmin thinks the DEFAULT_NET_SCH already made it happen) Whoops. My bad, probably - but.... The deeper question, part 1: There's this chunk in net/sched/Kconfig: config DEFAULT_NET_SCH string default "pfifo_fast" if DEFAULT_PFIFO_FAST default "fq" if DEFAULT_FQ default "fq_codel" if DEFAULT_FQ_CODEL default "fq_pie" if DEFAULT_FQ_PIE default "sfq" if DEFAULT_SFQ default "pfifo_fast" endif (And a similar chunk right above it with a similar issue) Should those be "if (foo=y)" so =m can't be chosen? (I'll be happy to write the patch if that's what we want) Deeper question, part 2: Should there be a way in the Kconfig language to ensure that these two chunks can't accidentally get out of sync? There's other places in the kernel where similar issues arise - a few days ago I was chasing a CPU governor issue where it looked like it was possible to set a default that was a module and thus possibly not actually loaded. --==_Exmh_1609618487_2273P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Comment: Exmh version 2.9.0 11/07/2018 iQIVAwUBX/DUNwdmEQWDXROgAQLg4Q/+L5yhR7DcbE3S76pyo00K3oJHl/tAchR3 f1EkfqQkxO/6x7TQotHGUiVoPmWpY96nBPt9yocTMD+RC9rNg2wv5EeCbozHak+B By6upU5lV/sLEMZ0G+ClOMdsbP3ppK1dAs6aD60VKikEXBfH/VA5SDXmK3gROPLx Yc9DGFbSZwFFQ8mtVO9gVJ7NSj06dDSUuZdxNpRzN0cpzcCOCWzktn7gDTw+3Jgt rPLEiTLSBM0IcK4PJ5gEypR7bVG1/223wHAXFgyJC+8AqJOsPLywri9AwUShi3mQ /u7nAiIo0Qlz/viIpde7bMN6RlKzQHcWvH7qus6hWZ5HOyc8UBE8bDXYSrr+YB83 E7IC5dv4deZuC1YDePkjWo7hKH+WaoKIYQsDK6MY+YQ7LbqxV4aqU+ecB6AYdZBc RYfUfFdKNDlkA/mWD0Ez+4OUMf6U/fXhaNwHXdUpTRqOF8TbsvzDc5g9sJOGGQZp 6eUYSH5vr+qI5CFSgcpKRzRf1wAzMS+jBmemzBlhIWaw9+aM6NcMhLU1a/iCE6Fm Q0U8hlzef3FqWFnAKchzCth+IpflCa8+bn6Ue7HqEyEyDMl3ej038xl4+kQSxLpI Krbl3VVGt8auExUsSVRHTUk/c+s178ARJf4KuDTeivSUSqv0bWQu+1CrRuZnX9Lv FDKICwWsjxQ= =SQQS -----END PGP SIGNATURE----- --==_Exmh_1609618487_2273P--