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Mon, 19 Oct 2026 02:05:12 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([195.174.134.4]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48dfd4f576asm23527360f8f.32.2026.10.19.02.05.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Oct 2026 02:05:12 -0700 (PDT) Message-ID: <0055967d4571e7c8549dfa476fa6b15b93013701.camel@redhat.com> Subject: Re: [PATCH v2 10/15] tools/rv: Add BPF monitors From: Gabriele Monaco To: John Ogness , Alexei Starovoitov , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, bpf@vger.kernel.org, Steven Rostedt Cc: Nam Cao , Wen Yang , Tobias Schaffner , Viktor Malik Date: Mon, 19 Oct 2026 11:05:10 +0200 In-Reply-To: <87ik2zryzo.fsf@jogness.linutronix.de> References: <20261001152042.124445-1-gmonaco@redhat.com> <20261001152042.124445-11-gmonaco@redhat.com> <878q3xtptq.fsf@jogness.linutronix.de> <8B3FF026-6159-48CF-8FEA-AF2FACD2E4EB@redhat.com> <87bj8s8ih9.fsf@jogness.linutronix.de> <87v770uuyr.fsf@jogness.linutronix.de> <87ik2zryzo.fsf@jogness.linutronix.de> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0BrZXJuZWwub3JnPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmjKX2MCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfIQuAD+JulczTN6l7oJjyroySU55Fbjdvo52xiYYlMjPG7dCTsBAMFI7dSL5zg98I+8 cXY1J7kyNsY6/dcipqBM4RMaxXsOtCRHYWJyaWVsZSBNb25hY28gPGdtb25hY29AcmVkaGF0LmNvb T6InAQTFgoARAIbAwUJBaOagAULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgBYhBMrKEfgLgd0WcK eo9u9KbElYeE3yBQJoymCyAhkBAAoJEO9KbElYeE3yjX4BAJ/ETNnlHn8OjZPT77xGmal9kbT1bC1 7DfrYVISWV2Y1AP9HdAMhWNAvtCtN2S1beYjNybuK6IzWYcFfeOV+OBWRDQ== User-Agent: Evolution 3.60.2 (3.60.2-2.fc44) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: KcMMGE-4j0wlMc4VKuH9bWLMuCY1y34q1yUhiygOEYE_1792400714 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2026-10-18 at 14:16 +0206, John Ogness wrote: > My issue with the /dev/kmsg design is bogus timestamps. But let's just > drop my suggestion to allow eBPF programs to call printk(). Since the RV > move to eBPF will require new user workflows anyway, the users will need > to learn these new packages, tools, and output sources. The important > thing (for me) is RV violations can still be used effectively with > ftrace/perf, which they can (using globs in bpf_trace:bpf_trace_printk > filters). Alright, I'll focus on trace_printk for now. As I said, it's rather trivial= to add another reactor later. > @gmonaco: There should be clean glob-friendly RV bpf_trace_printk > strings so that filters can be easily and reliably set up. If I leave the LTL header unmodified, you'd get something like: rv: sleep: [] violation detected It should be glob-friendly enough, but I'll try it out. I wonder if string matching brings additional overhead (trace_printk itself does, if I recall correctly), but that's probably rather minor. Gabriele