From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-vs1-f49.google.com (mail-vs1-f49.google.com [209.85.217.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 12F933191D3 for ; Sat, 27 Jun 2026 17:49:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.217.49 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782582571; cv=none; b=fe3uH/KvGV0fMYFsMr66A/bnoiIW4a08Te/i5qesVgH/5Li0+sveBwQKtGyyMhEVaL1IRjteYkVV+FBs4ajgmew9X5MRYVNTHq2RyTzN5L+ieOqv7eRR5ufimJms9JhMd5hcy4SLHB3ZV7y0KhA2t2aoLtq1uDFO38z48t1RiYI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782582571; c=relaxed/simple; bh=YA+1i/UnBYMi612cEFEOy+3MzER+Xfj7iA6l8jGXb4M=; h=From:Date:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=uqBWml+sZkZLyg3tgy3QWUrv+O87pvRvuZ80rDtczf5Wgo6yto2O9I/3FkFj/I+vhxgFODDK2NfOTzrlCZA2Jf6Ma0Q2cxq0emG7r4fRbVPkP/4UBoQKuhzsPUWPYpC5apcJmHKqjk27WwGuY+hwyQUVSRZrQ70/uoTpSELuNvI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=D+APVrVB; arc=none smtp.client-ip=209.85.217.49 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="D+APVrVB" Received: by mail-vs1-f49.google.com with SMTP id ada2fe7eead31-734dfaa3d9bso1368703137.3 for ; Sat, 27 Jun 2026 10:49:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1782582569; x=1783187369; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:from:to:cc:subject:date:message-id:reply-to; bh=+uflCN5dEoFADXWjqBtV9JZXNhAeBkbLG/4dD0z7b4I=; b=D+APVrVB7sDaioieVdmISDPXpLFAuW6Z8ACka+jIwp7ns0TQdWs5MEy+Z/dxvn8VAa e29T4yf7lV++S7Zg1KPGSJLqvjfqzUAvUEu7tSGmqaCsQogJoe9MO5ZfM/HH/GhY8ux0 YW6ZINIMDlm8qugBnJpjrCnTOHTSXKlAPJF11MzR2txP/MrDTMvFDy0oCu+HsC/1rWic 5RnQmKwAXJpxLkTmgZLfBFUKtZnCgcM2yM4bDprDEVL6jHCMPi1e3zAqIe9XmKpm9HEA GY5jXZXmdNMNEJwgCkWWPPLSrpsmhX+cbfcTpaZTE+Q/IJm4Gxe+tsxjkBwBxlPFhi9j 4y8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782582569; x=1783187369; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:date:from:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=+uflCN5dEoFADXWjqBtV9JZXNhAeBkbLG/4dD0z7b4I=; b=PqUUeIMu/4oZdKofwSZTUgDueZByIGmBD+b2u0JJOasSn8YAx96fQWL6JX9u+IsMHx njexukp3km429O9/cpKM3IQuBHKMWWrHkqqQVz+A+J7Au+/GaNkqJExyEqcW5T2WvbBN qhHEInK69VLVIzAgV08VSlwca4FzBi1i4j0imqqaRivIqNzvGk2QFUxAnPn3draet/bd oEXBlqhOi7DTl451MaAH2uP2kazBxTDQHLLMvOd8EbVqwZsbgFcvlhLu1umQIvJ0ETjX 8L/qr1/yRxl9mfIIhJCDKPDCbkjO3S4uRXsHvNEEADrIpdZE4CGXgY6T7wofHcVH1o7d KUIA== X-Forwarded-Encrypted: i=1; AHgh+RrMqlC7kDhY5+zes4eXh20HMAPIMpN6/0f7oU/bmgarLUX32++l01xoY91+IMyZFlBm9kQYMvMtH8K6@vger.kernel.org X-Gm-Message-State: AOJu0YwFMCPZQaAD6n345B2swilczIyjDLQLSBJnx2EKYieZo8A0alT+ qfHnxN+5J6Tq2Cg0gq85COiUmiXb5rjjJxvXSY/LfX2sOyVXlHPUdwNg X-Gm-Gg: AfdE7cklfAcYEMa7Mis7thDMeypUqm5j0hAWxtq9OdOkZfj0F5+S7INGtg6kk6SiKnD mvncVlioC2SGjSV0foTa68X5j65rzd851aZUvQunhRDb+JoZrU8qOSi42ewNPupTRNVHNcMX5G6 Wq4pp1L39eEMgt/aQGu5vjhArajj/YmmKh4GPXR1A+Wsz6j9FYj5DYxb6FFt7TDZiDkIiq2/l7h J2cPfIQd8Mk4xhnXo0jLnEehraj6cHAa/4nkEF0w71f7/prJo/te8ohRFh++mENlUsiF1sgFTEf sqPSxhXvDW72C00aqIpCoby//sDaaxIXG1ckfdQ1sAt/InhTg5wV1pe+/HLGJAQmGbq2twDjpxH 4FZCUffyLXa1nNPfS/tyQKedUTpWZRddw84fqiHGMLMoHxSXUcg+yT51VxiRU7nmb7tDNG0H3aF 9uJiE5peHNik2yzYMwE8kf/ESACSR2qg3MA4xrCnLuQ1Jf X-Received: by 2002:a05:6102:440f:b0:730:db02:1d08 with SMTP id ada2fe7eead31-73434452fd5mr5471882137.10.1782582569056; Sat, 27 Jun 2026 10:49:29 -0700 (PDT) Received: from localhost (d-24-145-72-22.fl.cpe.atlanticbb.net. [24.145.72.22]) by smtp.gmail.com with ESMTPSA id a1e0cc1a2514c-96916e5b10dsm2811280241.4.2026.06.27.10.49.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 27 Jun 2026 10:49:28 -0700 (PDT) From: Yury Norov X-Google-Original-From: Yury Norov Date: Sat, 27 Jun 2026 13:49:27 -0400 To: David Laight Cc: Robin Murphy , Andrew Morton , Rasmus Villemoes , Russell King , Frank Li , Sascha Hauer , Pengutronix Kernel Team , Fabio Estevam , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Ian Rogers , Adrian Hunter , James Clark , Thomas Gleixner , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , "Rafael J. Wysocki" , Len Brown , Greg Kroah-Hartman , Danilo Krummrich , Chanwoo Choi , MyungJoo Ham , Kyungmin Park , Heiko Stuebner , Lorenzo Pieralisi , Xu Yilun , Tom Rix , Moritz Fischer , Yicong Yang , Jonathan Cameron , Dennis Dalessandro , Jason Gunthorpe , Leon Romanovsky , Dan Williams , Vishal Verma , Dave Jiang , Ira Weiny , Bjorn Helgaas , Shuai Xue , Will Deacon , Jiucheng Xu , Neil Armstrong , Kevin Hilman , Jerome Brunet , Martin Blumenstingl , Jing Zhang , Xu Yang , Linu Cherian , Gowthami Thiagarajan , Ji Sheng Teoh , Khuong Dinh , Daniel Lezcano , Zhang Rui , Lukasz Luba , Yury Norov , Kees Cook , Thomas =?iso-8859-1?Q?Wei=DFschuh?= , Aboorva Devarajan , "Ritesh Harjani (IBM)" , Ilkka Koskinen , Besar Wicaksono , Ma Ke , Chengwen Feng , linux-arm-kernel@lists.infradead.org, imx@lists.linux.dev, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-perf-users@vger.kernel.org, linux-acpi@vger.kernel.org, driver-core@lists.linux.dev, linux-pm@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-fpga@vger.kernel.org, linux-rdma@vger.kernel.org, nvdimm@lists.linux.dev, linux-pci@vger.kernel.org, linux-amlogic@lists.infradead.org, linux-cxl@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH 13/16] perf: Use sysfs_emit() for cpumask show callbacks Message-ID: References: <20260528183625.870813-1-ynorov@nvidia.com> <20260528183625.870813-14-ynorov@nvidia.com> <7e980b99-1e4e-408b-8ebd-4d28116e7ad5@arm.com> <20260529130619.12f24264@pumpkin> Precedence: bulk X-Mailing-List: linux-rdma@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260529130619.12f24264@pumpkin> On Fri, May 29, 2026 at 01:06:19PM +0100, David Laight wrote: > On Fri, 29 May 2026 12:05:08 +0100 > Robin Murphy wrote: > > > On 2026-05-28 7:36 pm, Yury Norov wrote: > > > These callbacks are sysfs show paths. > > > > > > Use sysfs_emit() and cpumask_pr_args() to emit the masks. > > > > > > This prepares for removing cpumap_print_to_pagebuf(). > > > > TBH, looking at this diff I think it only shows the value of having a > > helper to abstract the boilerplate... > > > > I'm not sure I agree with the argument of removing something entirely > > just because it may occasionally be misused, but could we at least have > > something like: > > > > #define sysfs_emit_cpumask(buf, mask) \ > > sysfs_emit((buf), "%*pbl\n", cpumask_pr_args(mask)) > > > > to save the mess in all the many places where the current > > cpumap_print_to_pagebuf() usage _is_ entirely appropriate? This way you have to add 2 wrappers: #define sysfs_emit_cpulist(buf, mask) \ sysfs_emit((buf), "%*pbl\n", cpumask_pr_args(mask)) and #define sysfs_emit_cpumask(buf, mask) \ sysfs_emit((buf), "%*pb\n", cpumask_pr_args(mask)) There are people who complain even about DIV_ROUND_UP(), how hard it is to keep all that helpers in memory, and all that things. https://lore.kernel.org/all/20260304124805.GB2277644@noisy.programming.kicks-ass.net/ Disagree about DIV_ROUND_UP() (because yeah, I'm bad in math), but this sysfs_emit_cpumask() is a complete syntax redundancy. Once we have it, people will do this type of things: tmp = kmalloc(PAGE_SIZE); sysfs_emit_cpumask(tmp, mask); sysfs_emit(buf, "my prefix: %s\n", tmp); kfree(tmp); Patch #1 in this series is one example. My series that removes bitmap_print_to_pagebuf() will give you more: https://lore.kernel.org/all/20260303200842.124996-2-ynorov@nvidia.com/ It doesn't mean that *you* will misuse the API. It means that *I* will have to inspect the codebase for that type of bugs periodically. So, the overall state is simple: we've got well-established printf()-like functions that people know and understand, and we also have exotic APIs here and there with a non-standard interface and a clear potential to misuse. In this case, they have historical roots, but now we don't need them. > That has the advantage of letting you change how it is done (again) > without having to find all the callers. You mean things like silencing the prints or adding a prefix? If you believe that perf subsystem would benefit from it - that's OK. Just please keep it local. The kernel globally doesn't need to 'change how it is done' beyond the lib/vsprintf. The kernel really needs people to use something that the other people are familiar with. Thanks, Yury