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[2620:137:e000::1:20]) by mx.google.com with ESMTP id d31-20020a056402401f00b00459ff7667b4si3369768eda.203.2022.11.05.11.10.14; Sat, 05 Nov 2022 11:10:38 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@intel.com header.s=Intel header.b=PtTCtXZ8; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229863AbiKERkO (ORCPT + 99 others); Sat, 5 Nov 2022 13:40:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34452 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229517AbiKERkM (ORCPT ); Sat, 5 Nov 2022 13:40:12 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7EFBB1C938; Sat, 5 Nov 2022 10:40:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1667670011; x=1699206011; h=from:to:cc:subject:date:message-id; bh=YNstcQSEkgMBc3Az2kOerrMpu3CRH4Immut06G88wYs=; b=PtTCtXZ8oXDk6ikzs6KvqugGL3cGNR3SgsIQyJd9v3w4YmskIwmDYWLD cOm+C0muQk6/mtx9ucYmS/IdXUEpRNOGqWgjjAa5FsqOytlm5r6fX8AHp kVH+D8hqcjMZ3XXIGqpXTF9BxkeiRFk4XcvXU622m4d3lf99ooiA/7zwe QmqRx+dINADDlhIf29EKrhBMWuVp9ghJSsR0oZb6wVaWsSe++H3xWzY+i 95OsBygpEqkf38YagIm4aE5RHPACvh+QdT03r0Rrex5cOcFGmvrVDfZJ0 KntvFb2rw3dug9rXekkQBa6Olw1pIW313DObA21blaNWR5rSyosmE8LMG g==; X-IronPort-AV: E=McAfee;i="6500,9779,10522"; a="297672765" X-IronPort-AV: E=Sophos;i="5.96,140,1665471600"; d="scan'208";a="297672765" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 05 Nov 2022 10:40:10 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=McAfee;i="6500,9779,10522"; a="666729778" X-IronPort-AV: E=Sophos;i="5.96,140,1665471600"; d="scan'208";a="666729778" Received: from power-sh.sh.intel.com ([10.239.183.122]) by orsmga008.jf.intel.com with ESMTP; 05 Nov 2022 10:40:09 -0700 From: Zhang Rui To: rjw@rjwysocki.net, daniel.lezcano@linaro.org Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 1/3] cpuidle: ladder: Fix bogus comparison between s64 and u64 Date: Sun, 6 Nov 2022 01:42:23 +0800 Message-Id: <20221105174225.28673-1-rui.zhang@intel.com> X-Mailer: git-send-email 2.17.1 X-Spam-Status: No, score=-5.4 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1748680665729162354?= X-GMAIL-MSGID: =?utf-8?q?1748680665729162354?= ladder_device_state.threshold.promotion_time_ns/demotion_time_ns are u64 type. In ladder_select_state(), variable 'last_residency', as calculated by last_residency = dev->last_residency_ns - drv->states[last_idx].exit_latency_ns are s64 type, and it can be negative value. When this happens, comparing between 'last_residency' and 'promotion_time_ns/demotion_time_ns' become bogus. As a result, the ladder governor promotes or stays with current state errornously. -0 [001] d..1. 151.893396: ladder_select_state: last_idx 7, last_residency -373033 -0 [001] d..1. 151.893399: ladder_select_state: dev->last_residency_ns 106967, drv->states[last_idx].exit_latency_ns 480000 -0 [001] d..1. 151.893402: ladder_select_state: promote, last_state->threshold.promotion_time_ns 480000 -0 [001] d..1. 151.893404: ladder_select_state: ---> new state 7 -0 [001] d..1. 151.893465: ladder_select_state: last_idx 7, last_residency -463800 -0 [001] d..1. 151.893467: ladder_select_state: dev->last_residency_ns 16200, drv->states[last_idx].exit_latency_ns 480000 -0 [001] d..1. 151.893468: ladder_select_state: promote, last_state->threshold.promotion_time_ns 480000 -0 [001] dn.1. 151.893470: ladder_select_state: ---> new state 8 Given that promotion_time_ns/demotion_time_ns are initialized with cpuidle_state.exit_latency_ns, which is s64 type, and they are used to compare with 'last_residency', which is also s64 type, there is no reason to use u64 for promotion_time_ns/demotion_time_ns. With this patch, -0 [001] d..1. 523.578531: ladder_select_state: last_idx 8, last_residency -879453 -0 [001] d..1. 523.578531: ladder_select_state: dev->last_residency_ns 10547, drv->states[last_idx].exit_latency_ns 890000 -0 [001] d..1. 523.578532: ladder_select_state: demote , last_state->threshold.demotion_time_ns 890000 -0 [001] d..1. 523.578532: ladder_select_state: ---> new state 7 -0 [001] d..1. 523.580220: ladder_select_state: last_idx 7, last_residency -169629 -0 [001] d..1. 523.580221: ladder_select_state: dev->last_residency_ns 310371, drv->states[last_idx].exit_latency_ns 480000 -0 [001] d..1. 523.580221: ladder_select_state: demote , last_state->threshold.demotion_time_ns 480000 -0 [001] d..1. 523.580222: ladder_select_state: ---> new state 6 Signed-off-by: Zhang Rui --- drivers/cpuidle/governors/ladder.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/cpuidle/governors/ladder.c b/drivers/cpuidle/governors/ladder.c index 8e9058c4ea63..fb61118aef37 100644 --- a/drivers/cpuidle/governors/ladder.c +++ b/drivers/cpuidle/governors/ladder.c @@ -27,8 +27,8 @@ struct ladder_device_state { struct { u32 promotion_count; u32 demotion_count; - u64 promotion_time_ns; - u64 demotion_time_ns; + s64 promotion_time_ns; + s64 demotion_time_ns; } threshold; struct { int promotion_count;