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[212.8.243.115]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47a9e4d83bdsm58176872f8f.13.2026.07.10.01.27.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Jul 2026 01:27:30 -0700 (PDT) Message-ID: <0bc975ab8f3f7cf411ac0a5fa1c79d382827cdac.camel@redhat.com> Subject: Re: [PATCH 3/3] rv/reactors: add KUnit tests for reactor_panic From: Gabriele Monaco To: Wen Yang Cc: Nam Cao , linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 10 Jul 2026 10:27:28 +0200 In-Reply-To: <18dcc24d-329e-43f4-bc69-e368c1f1d066@linux.dev> References: <810f587d63c84b64067f990299be02b88f5d8106.1781541556.git.wen.yang@linux.dev> <18dcc24d-329e-43f4-bc69-e368c1f1d066@linux.dev> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0BrZXJuZWwub3JnPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmjKX2MCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfIQuAD+JulczTN6l7oJjyroySU55Fbjdvo52xiYYlMjPG7dCTsBAMFI7dSL5zg98I+8 cXY1J7kyNsY6/dcipqBM4RMaxXsOtCRHYWJyaWVsZSBNb25hY28gPGdtb25hY29AcmVkaGF0LmNvb T6InAQTFgoARAIbAwUJBaOagAULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgBYhBMrKEfgLgd0WcK eo9u9KbElYeE3yBQJoymCyAhkBAAoJEO9KbElYeE3yjX4BAJ/ETNnlHn8OjZPT77xGmal9kbT1bC1 7DfrYVISWV2Y1AP9HdAMhWNAvtCtN2S1beYjNybuK6IzWYcFfeOV+OBWRDQ== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2026-07-10 at 00:46 +0800, Wen Yang wrote: > Since rv_panic_reaction calls vpanic() which is __noreturn, direct=20 > testing is not feasible in KUnit. >=20 > A preparatory v2 drops reactor_printk_kunit.c and reactor_panic_kunit.c > entirely, replacing them with a single rv_reactors_kunit.c containing > two suites: >=20 > =C2=A0=C2=A0 rv_reactor_registration: register/unregister lifecycle, dupl= icate > =C2=A0=C2=A0=C2=A0=C2=A0 rejection (-EINVAL), name-too-long rejection, an= d safe unregister > =C2=A0=C2=A0=C2=A0=C2=A0 of a never-registered reactor. >=20 > =C2=A0=C2=A0 rv_react_dispatch: null-callback guard, callback invocation = check, > =C2=A0=C2=A0=C2=A0=C2=A0 and the mdelay lockdep stress test. >=20 >=20 > v2 also adds EXPORT_SYMBOL_GPL for rv_react(), rv_register_reactor(),=20 > and rv_unregister_reactor(), and the Kconfig entry is tristate. Alright, sounds good. > Additional fix: rv_unregister_reactor() >=20 > Testing exposed a real bug: rv_unregister_reactor() called list_del() > unconditionally.=C2=A0 On a never-registered reactor the list_head is > zero-initialised, so list_del() dereferences NULL->prev and crashes. > v2 adds a patch that iterates rv_reactors_list first and only calls > list_del() when the reactor is found.=C2=A0 test_unregister_nonexistent > documents and guards this behaviour. Mmh, besides unit testing, when can we even see a reactor unregistration be= fore it's ever registered? Do we really need to actively guard against this? What is probably an issue is to call unregistration also if registration fa= iled in reactors (which would cause the /bug/ you see, but shouldn't happen on current reactors anyway), we can fix that. I wouldn't guard against an issue that can only be triggered by broken code= . What am I missing? Thanks, Gabriele