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[2620:137:e000::1:20]) by mx.google.com with ESMTP id n8-20020a056402060800b004aef418518asi6544626edv.282.2023.02.26.19.17.44; Sun, 26 Feb 2023 19:18:06 -0800 (PST) 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; 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=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231177AbjB0Ciz (ORCPT + 99 others); Sun, 26 Feb 2023 21:38:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60034 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231689AbjB0Cil (ORCPT ); Sun, 26 Feb 2023 21:38:41 -0500 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0B1393C0C; Sun, 26 Feb 2023 18:38:09 -0800 (PST) Received: from kwepemm600003.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4PQ4NK73DVzKq8Z; Mon, 27 Feb 2023 10:35:13 +0800 (CST) Received: from ubuntu1804.huawei.com (10.67.174.61) by kwepemm600003.china.huawei.com (7.193.23.202) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.21; Mon, 27 Feb 2023 10:37:10 +0800 From: Yang Jihong To: , , , , , , , , , , CC: Subject: [PATCH RESEND v3] perf/core: Fix hardlockup failure caused by perf throttle Date: Mon, 27 Feb 2023 10:35:08 +0800 Message-ID: <20230227023508.102230-1-yangjihong1@huawei.com> X-Mailer: git-send-email 2.30.GIT MIME-Version: 1.0 X-Originating-IP: [10.67.174.61] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600003.china.huawei.com (7.193.23.202) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED, SPF_HELO_NONE,SPF_PASS 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?1758952566843846456?= X-GMAIL-MSGID: =?utf-8?q?1758952566843846456?= commit e050e3f0a71bf ("perf: Fix broken interrupt rate throttling") introduces a change in throttling threshold judgment. Before this, compare hwc->interrupts and max_samples_per_tick, then increase hwc->interrupts by 1, but this commit reverses order of these two behaviors, causing the semantics of max_samples_per_tick to change. In literal sense of "max_samples_per_tick", if hwc->interrupts == max_samples_per_tick, it should not be throttled, therefore, the judgment condition should be changed to "hwc->interrupts > max_samples_per_tick". In fact, this may cause the hardlockup to fail, The minimum value of max_samples_per_tick may be 1, in this case, the return value of __perf_event_account_interrupt function is 1. As a result, nmi_watchdog gets throttled, which would stop PMU (Use x86 architecture as an example, see x86_pmu_handle_irq). Fixes: e050e3f0a71b ("perf: Fix broken interrupt rate throttling") Signed-off-by: Yang Jihong --- Changes since v2: - Add fixed commit. Changes since v1: - Modify commit title. kernel/events/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index f79fd8b87f75..0540a8653906 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9434,7 +9434,7 @@ __perf_event_account_interrupt(struct perf_event *event, int throttle) } else { hwc->interrupts++; if (unlikely(throttle - && hwc->interrupts >= max_samples_per_tick)) { + && hwc->interrupts > max_samples_per_tick)) { __this_cpu_inc(perf_throttled_count); tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS); hwc->interrupts = MAX_INTERRUPTS;