From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752691AbbC1QQM (ORCPT ); Sat, 28 Mar 2015 12:16:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54489 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750855AbbC1QQI (ORCPT ); Sat, 28 Mar 2015 12:16:08 -0400 Message-ID: <5516D3BC.6030704@redhat.com> Date: Sat, 28 Mar 2015 12:15:56 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Frederic Weisbecker CC: LKML , Li Zefan , Tejun Heo , Greg Kroah-Hartman Subject: Re: [PATCH 2/2] show nohz_full cpus in sysfs References: <1427493027-15955-1-git-send-email-riel@redhat.com> <1427493027-15955-3-git-send-email-riel@redhat.com> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/28/2015 12:02 PM, Frederic Weisbecker wrote: > 2015-03-27 22:50 GMT+01:00 : >> From: Rik van Riel >> >> Currently there is no way to query which CPUs are in nohz_full >> mode from userspace. > > Well you can watch dmesg | grep NO_HZ > But surely sysfs is more convenient from an app. > > I guess it's ok, as long as it's strictly Read Only. Here it seems to > be the case. And it's not chmod'able, right? I followed the other code for files in that directory. Quick testing shows that the cpu info files in /sys/devices/system/cpu are chmoddable, but writing to them fails with -EIO because there is no function set up to handle writes. So yeah, read only :) -- All rights reversed