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([2620:10d:c090:500::7:b877]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2946dda72ddsm1605075ad.6.2025.10.22.15.04.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Oct 2025 15:04:52 -0700 (PDT) Message-ID: <93e428555500f60c3dbcb04b79807d3ffce024c5.camel@gmail.com> Subject: Re: [PATCH bpf-next v1] selftests/bpf: Add ABBCCA case for rqspinlock stress test From: Eduard Zingerman To: Kumar Kartikeya Dwivedi , bpf@vger.kernel.org Cc: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Martin KaFai Lau , kkd@meta.com, kernel-team@meta.com Date: Wed, 22 Oct 2025 15:04:51 -0700 In-Reply-To: <20251022175402.211176-1-memxor@gmail.com> References: <20251022175402.211176-1-memxor@gmail.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2025-10-22 at 17:54 +0000, Kumar Kartikeya Dwivedi wrote: > Introduce a new mode for the rqspinlock stress test that exercises a > deadlock that won't be detected by the AA and ABBA checks, such that we > always reliably trigger the timeout fallback. We need 4 CPUs for this > particular case, as CPU 0 is untouched, and three participant CPUs for > triggering the ABBCCA case. >=20 > Refactor the lock acquisition paths in the module to better reflect the > three modes and choose the right lock depending on the context. >=20 > Signed-off-by: Kumar Kartikeya Dwivedi > --- The overhaul makes sense to me and the code is easy to follow. The only nit I have is that test does not fail if deadlock is not detected. E.g. if I remove raw_res_spin_unlock_irqrestore() call in nmi_cb(), there are stall splats in dmesg, but test harness reports success. I suggest adding some signal that all kthreads terminated successfully. Acked-by: Eduard Zingerman [...]