From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756551Ab0EJKZ5 (ORCPT ); Mon, 10 May 2010 06:25:57 -0400 Received: from fgwmail5.fujitsu.co.jp ([192.51.44.35]:33210 "EHLO fgwmail5.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756432Ab0EJKZz (ORCPT ); Mon, 10 May 2010 06:25:55 -0400 X-SecurityPolicyCheck: OK by SHieldMailChecker v1.5.1 Message-ID: <9D38EE7159934A5C85505E9517638040@rainbow> From: "Iram Shahzad" To: References: <20090206060328.181057235@goodmis.org> Subject: hrtimer: about hres_active Date: Mon, 10 May 2010 19:27:06 +0900 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-2022-jp"; reply-type=original Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.5843 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.5579 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi I am trying to understand the purpose of "hres_active" of hrtimer and have the following question in this regard. It seems "hres_active" indicates whether high resolution mode is active or not. But I am not clear about the idea behind it. I see that hres_active is initialized to 0 here: hrtimer_init_hres and set to 1 here: hrtimer_run_pending -> hrtimer_switch_to_hres That means hrtimer becomes "active" at the 1st timer softirq and remains so forever. Is this understanding correct? My original concern is as follows: hrtimer_get_next_event returns KTIME_MAX when hrtimer is "active". So if the above understanding is correct, then after the 1st timer softirq it will always return KTIME_MAX. This means cpu_idle will never take the hrtimer event into account and will always base its decision on the next event of the timer wheel. Is this intended behaviour? I would highly appreciate any information about this. Please CC me because I am not a member of this ML. Best regards Iram