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[212.8.243.115]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482b14c3775sm3207741f8f.26.2026.08.19.00.12.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Aug 2026 00:12:45 -0700 (PDT) Message-ID: Subject: Re: [PATCH v3 1/4] rv/reactors: use context-sensitive lockdep wait type in rv_react() From: Gabriele Monaco To: Nam Cao , wen.yang@linux.dev Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas =?ISO-8859-1?Q?Wei=DFschuh?= Date: Wed, 19 Aug 2026 09:12:43 +0200 In-Reply-To: <87zeylnos3.fsf@yellow.woof> References: <26526e555baa5118325b2383e9f7f0f8f9b6a199.1786294920.git.wen.yang@linux.dev> <38decc4f7ef5b6f03b37705c7e97f22a7e40d7e2.camel@redhat.com> <87zeylnos3.fsf@yellow.woof> 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 Mon, 2026-08-17 at 10:18 +0200, Nam Cao wrote: > Gabriele Monaco writes: >=20 > > On Mon, 2026-08-10 at 01:10 +0800, wen.yang@linux.dev=C2=A0wrote: > > > From: Wen Yang > > >=20 > > > Reactors must not explicitly take locks, so they should comply with > > > LD_WAIT_FREE.=C2=A0 However, reactor callbacks can run with preemptio= n > > > enabled on any kernel (not just PREEMPT_RT).=C2=A0 If a timer interru= pt > > > fires during the callback, the interrupt exit path schedules and > > > acquires rq->__lock (LD_WAIT_SPIN) while the lockdep override map tha= t > > > declared LD_WAIT_FREE is still held, triggering a spurious > > > "Invalid wait context" warning: > ... > > Anyway, I'd appreciate comments/acks from the other folks in the loop >=20 > Sorry, I do not know enough about lockdep to comment on this. >=20 > FWIW, I would rather just use LD_WAIT_SPIN and keep things > simple. Context-sensitive code paths "feels wrong" to me. Spinning > should either be allowed or forbidden. Making it dynamic "feels like" it > will bring further complications down the road. >=20 > But that's just my intuition. I don't have a strong opinion on this, but since there's no one in the kern= el using LD_WAIT_FREE as inner type, that feels like a hint to go down the sim= ple route too and allow LD_WAIT_SPIN. If a reactor ever uses spinlocks, lockdep would already complain on its own= if that ends up being an issue, wouldn't it? Gabriele