From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A7D1C2E9ECA for ; Mon, 13 Oct 2025 07:30:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760340633; cv=none; b=MSbO3xX37u8e8N3/rHGPnCGPbiX9JYBfIRDkmjByyqfHLf3tAxb16HQsnG08MX4kGXwPo+HZR/9v1zG5IxwxhMCblavsj3DY0yjFzAimibOJXs51zD04338t4mv+/a6o+7YiSc5AZhJP+WrhHNYJM+XQncF99s4u/QAfl6MWm+Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760340633; c=relaxed/simple; bh=7hKulDyCiG2MZUrEpJuX55XdK4d3NXy+qGwlTfVda+Q=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=I3aQyftPPzT7UNZvnhiphM3O5jj/mCtxDxkoXuxkQ+5YGPcC8vaqUMyqbDqo13+2yQFyE4ttqwIm1DTl0Ji08Q+AdEutS2puDdyoUeKcA4hLncg8uiVU5Ojc+7n/87NEAXZNMXGWwp2wv0V3WdZAanXtFVaTNth5kSBk8Ondd6I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=B8UnPVfQ; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="B8UnPVfQ" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1760340630; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=jvcrm6KIUPUNpc7xmiZElApRSjY4cVtEn4dAkTy/70Q=; b=B8UnPVfQ9+61fnzki8AGahmrz3uL7Itgl/vUl01KV1td38bFseJds3Cj93BPlCA71/xTNP OHBCai8loIfrVpchdihMMt8DK4bKoBk/xyV8KITgRifY7FHbwarXBfJw5/DbOC2qQWhSUw pMzS49IcogthepLBzu496Ewi4KR4V3Y= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-682-2M0Gteh4OSODRO7zJSlXWQ-1; Mon, 13 Oct 2025 03:30:29 -0400 X-MC-Unique: 2M0Gteh4OSODRO7zJSlXWQ-1 X-Mimecast-MFC-AGG-ID: 2M0Gteh4OSODRO7zJSlXWQ_1760340628 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-46e4cb3e4deso14494495e9.1 for ; Mon, 13 Oct 2025 00:30:28 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760340628; x=1760945428; h=mime-version:user-agent:content-transfer-encoding:autocrypt :references:in-reply-to:date:cc:to:from:subject:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=jvcrm6KIUPUNpc7xmiZElApRSjY4cVtEn4dAkTy/70Q=; b=vGUjRm+nZOZPo7PkM1HZ5a5FGRZGZKIeoIF7jqQAeKsh+YIZUlH0ByM/psMW/nei+c VWrVld49JuW8Cj5xeFRRHScDwN/9T//axFLGoQ9NI7XBZ7Q+LDlkaNdhcTlp5bzH5Ro7 aBOaCQ297/u+hHq3Ve2McbQlGSxi/XEHfGGoCNr/Y/GqE50vD/2u0pAV6CI0Zn+C4Sjn NfBlUfb+woNBv857t03jfxWBxA5YaUIC1P+WfFavnEpj9BKd6DEM30YuQ9FjFdzZ0Owx g0vmR7YvC/w9slypK2rb8u3n+s7CudKceVDQg+GDQn068ccR1tr+K34XtJpKLdBiEMI6 AUBw== X-Forwarded-Encrypted: i=1; AJvYcCW93LY9Gm9oouZ041PziRLwatBWhMrJPb63lRGdaWqcBsKCI1ydQnXWACziungn4O76JH1EteAG2dWYDFc=@vger.kernel.org X-Gm-Message-State: AOJu0YyiKhDecJox/SHDB/80/iFGdLnvThMiMIOR1vnTmo0fOirtd/Qk UK4K383EuhaJtLSHADkc2qndwqG2pDt5iuW/n4g6oh2jIOWcGRiG5yXQ+o5N4MPtFAgTggGbY/q ho23ScLk9bUfa9jBIXRDyKnABTdH9v++sRgn85wLi11VgyuZ7+zfN7hFipsC8gzMSXwoMRSPeVE oB X-Gm-Gg: ASbGncs0YjkUiP0B/ZKuU53Vkrhwff6EMxX4O3ltFy1EKZnwBANihPUIiEfF4vvMroE dRqPBtcraPgOJQfVTuNyYEQgm6s9nn9EgnH4txYMAF+zuFg1W5slZTft6QCKDCprjAQbV8ScwDm hGbvlWYClyhsKTTR2LtxYWegSQ3kRdsMiNOEfe7HxMAIE6xhuEuwA0rA5mfDJ9UEq6uL+0bmZMA pHO4iaxwP4RhMRQdA7CZtR7jtpgu8TzqChIJoIarN/UCwUBl+1bm4s12atbeRoZSM5VmdeTX/wf +GsE85x5eROHy3BchrdlTw2HcSA1itS2PPpSFfd1Lls4XzM2wt3JnPC96V6jh2Lmvg== X-Received: by 2002:a05:600d:824b:b0:46f:c55e:a687 with SMTP id 5b1f17b1804b1-46fc55ea6f7mr15279195e9.7.1760340627724; Mon, 13 Oct 2025 00:30:27 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEC/F6R+8hlK3CtQbemkFUUvDibbdW2qqB3BO9HixY7B8LvjUh+PY8O3sgUpuovPDwK9I3d/A== X-Received: by 2002:a05:600d:824b:b0:46f:c55e:a687 with SMTP id 5b1f17b1804b1-46fc55ea6f7mr15279035e9.7.1760340627301; Mon, 13 Oct 2025 00:30:27 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.30]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fab3d2c1asm121363435e9.1.2025.10.13.00.30.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Oct 2025 00:30:26 -0700 (PDT) Message-ID: <646db9e9d956f009d53bfabf8b8287c034279066.camel@redhat.com> Subject: Re: [PATCH v2 20/20] rv: Add deadline monitors From: Gabriele Monaco To: Nam Cao , linux-kernel@vger.kernel.org, Steven Rostedt , Jonathan Corbet , Masami Hiramatsu , linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org Cc: Tomas Glozar , Juri Lelli , Clark Williams , John Kacur Date: Mon, 13 Oct 2025 09:30:24 +0200 In-Reply-To: <87a51yyf0o.fsf@yellow.woof> References: <20250919140954.104920-1-gmonaco@redhat.com> <20250919140954.104920-21-gmonaco@redhat.com> <87a51yyf0o.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 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-10-10 at 17:04 +0200, Nam Cao wrote: > Gabriele Monaco writes: > > +/* > > + * Dummy values if not available > > + */ > > +#ifndef __NR_sched_setscheduler > > +#define __NR_sched_setscheduler -1 > > +#endif > > +#ifndef __NR_sched_setattr > > +#define __NR_sched_setattr -2 > > +#endif >=20 > You can use __COUNTER__ intead, would make it easier to add to or remove > from this list later on. Right, good point. > > +static void handle_syscall(void *data, struct pt_regs *regs, long id) > > +{ > > + struct task_struct *p; > > + int new_policy =3D -1; > > + > > + new_policy =3D extract_params(regs, id, &p); > > + if (new_policy < 0 || new_policy =3D=3D p->policy) > > + return; > > + if (p->policy =3D=3D SCHED_DEADLINE) > > + da_reset(EXPAND_ID(&p->dl, DL_TASK)); > > + else if (new_policy =3D=3D SCHED_DEADLINE) > > + da_create_conditional(EXPAND_ID(&p->dl, DL_TASK), > > GFP_NOWAIT); > > +} >=20 > What if the syscall fails for any reason? Wouldn't the monitor stores > incorrect information? Yes, that could happen, this seems an issue only in the throttle monitor wh= en failing a DEADLINE->NORMAL, other cases are at most resetting the monitor. In this case, the monitor is really saying: a deadline task is no longer deadline, so its runtime should be counted as fair server. If the syscall d= oes fail, we are assuming the fair server as armed (not running) for a bit more= . Here I couldn't find a nice way to handle this: if I attach only to the sys= call return, I see if it succeeded but I lost the previous policy, attaching to = both (and keep a per-cpu storage just for this process) seems a bit overcomplica= ted. I see this can potentially lead to errors in the monitor, but I'm not sure = the extra complexity is worth it here, considering this failure might only happ= en if a user really makes wrong calls. I tried to avoid creating a new tracepoint on a successful policy change. What do you think? Thanks, Gabriele