From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtpout.efficios.com (smtpout.efficios.com [167.114.26.122]) by sourceware.org (Postfix) with ESMTPS id 559043858C66 for ; Thu, 12 Jan 2023 20:25:10 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 559043858C66 Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=efficios.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=efficios.com; s=smtpout1; t=1673555108; bh=ABVJWX1YFWwFvWg/I5xwpsfT16mnlQwmI7g0C+2Jyn4=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ojAdu+SEv3o0qPtQaYvRGeG2uLn5uKtQiXcB6KTM8h+Up41sF+U9Zx30cyDFDM+qL LDG5NyFvVCO4jjBEcBz22rctcdkokAyB1pMBrnCeEaVsx9WVh/f9jKOVA7wnL4DDOl tcMN2GybZ2mLvJMu93TI5WMZFsmdQl0uhCSsXeYeHWy2GoSJsJHJsdCD7ffRR1zN3B +ZpGR0poS6xwbmBnFXvwDKewIemlOq2Wa4FRlG5sZ37wDWHO2RZSIrm7Zbl2Fhc6fD 0nalsyGAGfmnQQ11U+kVZnmR+W6biaK4SK0UfiywloZmvBMynVfAafhQPTJZi+ezcE gySTVsWSA0Kuw== Received: from [172.16.0.101] (192-222-180-24.qc.cable.ebox.net [192.222.180.24]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4NtGJ42rQ1zg6p; Thu, 12 Jan 2023 15:25:08 -0500 (EST) Message-ID: <5c64b742-c41a-8c59-c0c8-8b4cdedaaba5@efficios.com> Date: Thu, 12 Jan 2023 15:25:42 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: rseq CPU ID not correct on 6.0 kernels for pinned threads Content-Language: en-US To: Florian Weimer Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Peter Zijlstra , libc-alpha@sourceware.org References: <87lem9cnxr.fsf@oldenburg.str.redhat.com> <8b52b0d6-c973-f959-b44a-1b54fb808a04@efficios.com> <871qnzpv9l.fsf@oldenburg.str.redhat.com> From: Mathieu Desnoyers In-Reply-To: <871qnzpv9l.fsf@oldenburg.str.redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-1.1 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,NICE_REPLY_A,SPAM_BODY,SPF_HELO_NONE,SPF_PASS,TXREP autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 2023-01-12 11:33, Florian Weimer wrote: > * Mathieu Desnoyers: > >> As you also point out, it can also be caused by some other task >> modifying the affinity of your task concurrently. You could print >> the result of sched_getaffinity on error to get a better idea of >> the expected vs actual mask. >> >> Lastly, it could be caused by CPU hotplug which would set all bits >> in the affinity mask as a fallback. As you mention it should not be >> the cause there. >> >> Can you share your kernel configuration ? > > Attached. > > cpupower frequency-info says: > > analyzing CPU 0: > driver: intel_cpufreq > CPUs which run at the same hardware frequency: 0 > CPUs which need to have their frequency coordinated by software: 0 > maximum transition latency: 20.0 us > hardware limits: 800 MHz - 4.60 GHz > available cpufreq governors: conservative ondemand userspace powersave performance schedutil > current policy: frequency should be within 800 MHz and 4.60 GHz. > The governor "schedutil" may decide which speed to use > within this range. > current CPU frequency: Unable to call hardware > current CPU frequency: 3.20 GHz (asserted by call to kernel) > boost state support: > Supported: yes > Active: yes > > And I have: kernel.sched_energy_aware = 1 > >> Is this on a physical machine or in a virtual machine ? > > I think it happened on both. > > I added additional error reporting to the test (running on kernel > 6.0.18-300.fc37.x86_64), and it seems that there is something that is > mucking with affinity masks: > > info: Detected CPU set size (in bits): 64 > info: Maximum test CPU: 19 > error: Pinned thread 17 ran on impossible cpu 7 > info: getcpu reported CPU 7, node 0 > info: CPU affinity mask: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 > error: Pinned thread 3 ran on impossible cpu 13 > info: getcpu reported CPU 13, node 0 > info: CPU affinity mask: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 > info: Main thread ran on 2 CPU(s) of 20 available CPU(s) > info: Other threads ran on 20 CPU(s) > > For each of these threads, the affinity mask should be a singleton set. > Now I need to find out if there is a process that changes affinity > settings. If it's not cpu hotunplug, then perhaps something like systemd modifies the AllowedCPUs of your cpuset concurrently ? Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. https://www.efficios.com