From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id ABF68C4332F for ; Wed, 12 Oct 2022 13:13:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229484AbiJLNNr (ORCPT ); Wed, 12 Oct 2022 09:13:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55132 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229590AbiJLNNo (ORCPT ); Wed, 12 Oct 2022 09:13:44 -0400 Received: from mail-ed1-x532.google.com (mail-ed1-x532.google.com [IPv6:2a00:1450:4864:20::532]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6CFE080BF0 for ; Wed, 12 Oct 2022 06:13:28 -0700 (PDT) Received: by mail-ed1-x532.google.com with SMTP id m15so24358444edb.13 for ; Wed, 12 Oct 2022 06:13:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ventanamicro.com; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=Qec+PTzHVRJaCTYLMbLbFJcUxjGagA3lcOkRy3Fcpa0=; b=H8ZXF5cgpFfTnH9WMmsidkLVvJGK2QRQafdmcsaxlacZ0dMT33o30zQOTesinRlBQt Upa2RzZRvOczcNg3VHcZ3/QmtScT7DVwDYnnwJv6RD/jinZ9RkfDNf+fefI4vWIGQOyd mG5Bej+3NVpguxNW0668vRbI/oFDyRdAbRH3GgfYNWSvQXT3nt8Z2fAB9Ih9dPKJ5uVM 66xv++Ydk8nARhfySiRM2XRkF0X6R6PG3rTr+FvlhOUQ1wjQqeLGwbD5hB0YXfHn/WLG LG8Q71jcieCDM4asn7V9LOUVFHG4ueEMWNdlIfKZQNU7CnVWoE1fobla2Y6rOx+VZtnP 7nMw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Qec+PTzHVRJaCTYLMbLbFJcUxjGagA3lcOkRy3Fcpa0=; b=UKOUSWxJscZd1I+c3hip64rTsmpb+Xaf9OunEvXaV/8U9bPbVMnRyOM4KgR5N1I+7Y kL/OeIFzopq4o8WbSg8CrOguk9vZ0K1nkM2SFN83TItry9S7b3xDnPjN4sfZPx+t7PlE qz7VZJvlrUjl0/lBqbboDrECmQ9LVYar/gx465DIGl0kiL8XBVBlgJoeFuhMxhibMk66 Azk45DjSyTNTzYkZHIRYNO7B/e43N+me0XBwlQ+XT8ZKjGrQBWjcWJrbRogtnLUW5acA qP7zvvOIWhtEFxX/w8exmCr8Z18fs+/wud6Z3k5XfTAQevKWi0KBU4kFUdyPRXSUt/t7 oryg== X-Gm-Message-State: ACrzQf3sUA71IrLbtwGNN/FIA0WsS3Kxi5DvRqJW2u/aGfT3PM4pxjAl UIIagi+n3mrgxvFnTK1OS3nBmg== X-Google-Smtp-Source: AMsMyM4Z8GIXaJySZvnILH18H+0/tiWIyJ+Goli8Iw3sXUFq88849aAGyyIj+faT/QC287JNERqTvA== X-Received: by 2002:a05:6402:5256:b0:459:42b3:3d86 with SMTP id t22-20020a056402525600b0045942b33d86mr26362820edd.370.1665580406476; Wed, 12 Oct 2022 06:13:26 -0700 (PDT) Received: from localhost (cst2-173-61.cust.vodafone.cz. [31.30.173.61]) by smtp.gmail.com with ESMTPSA id v1-20020a1709067d8100b0078d957e65b6sm1279316ejo.23.2022.10.12.06.13.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Oct 2022 06:13:26 -0700 (PDT) Date: Wed, 12 Oct 2022 15:13:25 +0200 From: Andrew Jones To: Yury Norov Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Palmer Dabbelt , Paul Walmsley , Albert Ou Subject: Re: [PATCH v2] RISC-V: Fix /proc/cpuinfo cpumask warning Message-ID: <20221012131325.oc7onxqo7t46wxq5@kamzik> References: <20221012082949.1801222-1-ajones@ventanamicro.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 12, 2022 at 05:55:29AM -0700, Yury Norov wrote: > On Wed, Oct 12, 2022 at 10:29:49AM +0200, Andrew Jones wrote: > > Commit 78e5a3399421 ("cpumask: fix checking valid cpu range") has > > started issuing warnings[*] when cpu indices equal to nr_cpu_ids - 1 > > are passed to cpumask_next* functions. seq_read_iter() and cpuinfo's > > start and next seq operations implement a pattern like > > > > n = cpumask_next(n - 1, mask); > > show(n); > > while (1) { > > ++n; > > n = cpumask_next(n - 1, mask); > > if (n >= nr_cpu_ids) > > break; > > show(n); > > } > > Can you instead of sudo-code print show the real control flow? What > function hosts the infinite loop? The function is seq_read_iter(), which is pointed out above. I'd rather not reproduce / describe more than what I've done here, as the function is large. I'd be happy for reviewers to double check my pseudocode to make sure I got it and the analysis right, though. > > > which will issue the warning when reading /proc/cpuinfo. Ensure no > > warning is generated by validating the cpu index before calling > > cpumask_next(). > > > > [*] Warnings will only appear with DEBUG_PER_CPU_MAPS enabled. > > > > Signed-off-by: Andrew Jones > > Cc: Yury Norov > > --- > > v2: > > - Got comments on the x86 equivalent patch and made the same > > changes to this one > > - Added all the information I should have in the first place > > to the commit message [Boris] > > - Changed style of fix [Boris] > > > > > > arch/riscv/kernel/cpu.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c > > index 4aa8cd749441..63138b880b92 100644 > > --- a/arch/riscv/kernel/cpu.c > > +++ b/arch/riscv/kernel/cpu.c > > @@ -166,6 +166,9 @@ static void print_mmu(struct seq_file *f) > > > > static void *c_start(struct seq_file *m, loff_t *pos) > > { > > + if (*pos >= nr_cpu_ids) > > + return NULL; > > + > > *pos = cpumask_next(*pos - 1, cpu_online_mask); > > if ((*pos) < nr_cpu_ids) > > return (void *)(uintptr_t)(1 + *pos); > > OK, as far as I understood your explanations, *pos == nr_cpu_ids > is a valid index because it's used as stop-code for traversing. > > However, you're completely silencing cpumask_check(), including > those cases where *pos > nr_cpu_ids. I suspect there's no valid > cases for it. If so, the patch should look like: > > + if (*pos == nr_cpu_ids) > + return NULL; > + That makes sense and it's probably worth a v3. I'll wait and see if more comments roll in before sending though. > > The same for x86 patch. > > If it comes to v3, can you send both as a series? OK. I'll write a cover letter trying to explain that I don't expect them to both go through the same tree. Thanks, drew