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Tue, 29 Jul 2025 01:46:54 -0700 (PDT) X-Google-Smtp-Source: AGHT+IENm4rGB9QH5ZR2b+CQxX8IopxI/UqZi4w2Zrp9xW5q/tHuwjGtN0qFNHlnuI29FnnDzuK6cw== X-Received: by 2002:a05:600c:a088:b0:456:1608:c807 with SMTP id 5b1f17b1804b1-4588adc3677mr39809655e9.26.1753778814422; Tue, 29 Jul 2025 01:46:54 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.42]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b78dd6cb0fsm2299807f8f.29.2025.07.29.01.46.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 29 Jul 2025 01:46:53 -0700 (PDT) Message-ID: <76d7e572aae2ccd1699a461aded7a6146f6d8215.camel@redhat.com> Subject: Re: [PATCH v5 7/9] rv: Replace tss and sncid monitors with more complete sts From: Gabriele Monaco To: Nam Cao Cc: linux-kernel@vger.kernel.org, Steven Rostedt , linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Ingo Molnar , Peter Zijlstra , Tomas Glozar , Juri Lelli , Clark Williams , John Kacur Date: Tue, 29 Jul 2025 10:46:51 +0200 In-Reply-To: <20250728155332.sbkepHj7@linutronix.de> References: <20250728135022.255578-1-gmonaco@redhat.com> <20250728135022.255578-8-gmonaco@redhat.com> <20250728155332.sbkepHj7@linutronix.de> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP 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: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2025-07-28 at 17:53 +0200, Nam Cao wrote: > I gave this a try on riscv64 and observed some errors: >=20 > [=C2=A0 620.696055] rv: monitor sts does not allow event sched_switch on > state enable_to_exit > [=C2=A0 621.047705] rv: monitor sts does not allow event sched_switch on > state enable_to_exit > [=C2=A0 642.440209] rv: monitor sts does not allow event sched_switch on > state enable_to_exit >=20 > I tested with two user programs: >=20 > =C2=A0=C2=A0=C2=A0 int main() { asm ("unimp"); } > =C2=A0=C2=A0=C2=A0 int main() { asm ("ebreak"); } >=20 > The two programs are repeatedly executed: >=20 > =C2=A0=C2=A0=C2=A0 #!/bin/bash > =C2=A0=C2=A0=C2=A0 ./test1 & > =C2=A0=C2=A0=C2=A0 ./test2 & > =C2=A0=C2=A0=C2=A0 # ... repeat lots of time >=20 > Any idea? Mmh I see what you're doing here.. Those instructions are supposed to raise some sort of exception in the CPU which apparently disables and enables interrupts without raising an interrupt handler tracepoint (the discriminator for this monitor). This lets the monitor believe we passed the time a switch is possible and complain when it actually sees one. I still couldn't reproduce it on my VM, yet I find the timing a bit strange: it's alright we handle the illegal instruction like this, but do we really end up doing that while scheduling although it doesn't look like an interrupt?! Could you share a bit more about your riscv setup? It might some configuration/hardware specific thing. Thanks for finding this, Gabriele