From patchwork Wed May 4 12:01:10 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 9012861 X-Patchwork-Delegate: rjw@sisk.pl Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 2E3E09F39D for ; Wed, 4 May 2016 11:58:05 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 3FDA920396 for ; Wed, 4 May 2016 11:58:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 57C59203A0 for ; Wed, 4 May 2016 11:58:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751981AbcEDL6B (ORCPT ); Wed, 4 May 2016 07:58:01 -0400 Received: from cloudserver094114.home.net.pl ([79.96.170.134]:62921 "HELO cloudserver094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751629AbcEDL6A (ORCPT ); Wed, 4 May 2016 07:58:00 -0400 Received: from 217.96.255.101.ipv4.supernova.orange.pl (217.96.255.101) (HELO vostro.rjw.lan) by serwer1319399.home.pl (79.96.170.134) with SMTP (IdeaSmtpServer v0.80.2) id 4fcaa7bd7488f26e; Wed, 4 May 2016 13:57:58 +0200 From: "Rafael J. Wysocki" To: Peter Zijlstra , Linux PM list Cc: kernel test robot , Steve Muckle , lkp@01.org, linux-kernel@vger.kernel.org, Vincent Guittot , Thomas Gleixner , "Rafael J. Wysocki" , Patrick Bellasi , Morten Rasmussen , Mike Galbraith , Michael Turquette , Juri Lelli , Dietmar Eggemann , Steve Muckle , Ingo Molnar , Srinivas Pandruvada Subject: [PATCH] intel_pstate: Fix intel_pstate_get() Date: Wed, 04 May 2016 14:01:10 +0200 Message-ID: <54177738.QIcPrzf0Y7@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/4.5.0-rc1+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20160503083231.GG3430@twins.programming.kicks-ass.net> References: <87mvo8gd44.fsf@yhuang-dev.intel.com> <20160503083231.GG3430@twins.programming.kicks-ass.net> MIME-Version: 1.0 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org X-Spam-Status: No, score=-9.0 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP From: Rafael J. Wysocki After commit 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" intel_pstate_get() calls get_avg_frequency() to compute the average frequency, which is problematic for two reasons. First, intel_pstate_get() may be invoked before the driver reads the CPU feedback registers for the first time and if that happens, get_avg_frequency() will attempt to divide by zero. Second, the get_avg_frequency() call in intel_pstate_get() is racy with respect to intel_pstate_sample() and it may end up returning completely meaningless values for this reason. Moreover, after commit 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" sample.core_pct_busy is never computed on Atom, but it is used in intel_pstate_adjust_busy_pstate() in that case too. To address those problems notice that if sample.core_pct_busy was used in the average frequency computation carried out by get_avg_frequency(), both the divide by zero problem and the race with respect to intel_pstate_sample() would be avoided. Accordingly, move the invocation of intel_pstate_calc_busy() from get_target_pstate_use_performance() to intel_pstate_update_util(), which also will take care of the uninitialized sample.core_pct_busy on Atom, and modify get_avg_frequency() to use sample.core_pct_busy as per the above. Reported-by: kernel test robot Link: http://marc.info/?l=linux-kernel&m=146226437623173&w=4 Fixes: 8fa520af5081 "intel_pstate: Remove freq calculation from intel_pstate_calc_busy()" Fixes: 7349ec0470b6 "intel_pstate: Move intel_pstate_calc_busy() into get_target_pstate_use_performance()" Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/intel_pstate.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Index: linux-pm/drivers/cpufreq/intel_pstate.c =================================================================== --- linux-pm.orig/drivers/cpufreq/intel_pstate.c +++ linux-pm/drivers/cpufreq/intel_pstate.c @@ -928,8 +928,9 @@ static inline bool intel_pstate_sample(s static inline int32_t get_avg_frequency(struct cpudata *cpu) { - return div64_u64(cpu->pstate.max_pstate_physical * cpu->sample.aperf * - cpu->pstate.scaling, cpu->sample.mperf); + return fp_toint(mul_fp(cpu->sample.core_pct_busy, + int_tofp(cpu->pstate.max_pstate_physical * + cpu->pstate.scaling / 100))); } static inline int32_t get_target_pstate_use_cpu_load(struct cpudata *cpu) @@ -972,8 +973,6 @@ static inline int32_t get_target_pstate_ int32_t core_busy, max_pstate, current_pstate, sample_ratio; u64 duration_ns; - intel_pstate_calc_busy(cpu); - /* * core_busy is the ratio of actual performance to max * max_pstate is the max non turbo pstate available @@ -1056,8 +1055,11 @@ static void intel_pstate_update_util(str if ((s64)delta_ns >= pid_params.sample_rate_ns) { bool sample_taken = intel_pstate_sample(cpu, time); - if (sample_taken && !hwp_active) - intel_pstate_adjust_busy_pstate(cpu); + if (sample_taken) { + intel_pstate_calc_busy(cpu); + if (!hwp_active) + intel_pstate_adjust_busy_pstate(cpu); + } } }