From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 87451C433EF for ; Thu, 24 Mar 2022 14:14:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350773AbiCXOPx (ORCPT ); Thu, 24 Mar 2022 10:15:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45474 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350758AbiCXOPw (ORCPT ); Thu, 24 Mar 2022 10:15:52 -0400 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CDDA21FCD0; Thu, 24 Mar 2022 07:14:16 -0700 (PDT) X-UUID: 0aa1160529f245fdb62e2fb6ad6abbe5-20220324 X-UUID: 0aa1160529f245fdb62e2fb6ad6abbe5-20220324 Received: from mtkmbs10n1.mediatek.inc [(172.21.101.34)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-GCM-SHA384 256/256) with ESMTP id 1102049120; Thu, 24 Mar 2022 22:14:10 +0800 Received: from mtkcas11.mediatek.inc (172.21.101.40) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id 15.2.792.15; Thu, 24 Mar 2022 22:14:09 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas11.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Thu, 24 Mar 2022 22:14:08 +0800 From: Lecopzer Chen To: CC: , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: [PATCH v3 0/5] Support hld delayed init based on Pseudo-NMI for arm64 Date: Thu, 24 Mar 2022 22:14:00 +0800 Message-ID: <20220324141405.10835-1-lecopzer.chen@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 Content-Type: text/plain X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-perf-users@vger.kernel.org As we already used hld internally for arm64 since 2020, there still doesn't have a proper commit on the upstream and we badly need it. This serise rework on 5.17 from [1] and the origin author is Pingfan Liu Sumit Garg Qoute from [1]: > Hard lockup detector is helpful to diagnose unpaired irq enable/disable. > But the current watchdog framework can not cope with arm64 hw perf event > easily. > On arm64, when lockup_detector_init()->watchdog_nmi_probe(), PMU is not > ready until device_initcall(armv8_pmu_driver_init). And it is deeply > integrated with the driver model and cpuhp. Hence it is hard to push the > initialization of armv8_pmu_driver_init() before smp_init(). > But it is easy to take an opposite approach by enabling watchdog_hld to > get the capability of PMU async. > The async model is achieved by expanding watchdog_nmi_probe() with > -EBUSY, and a re-initializing work_struct which waits on a > wait_queue_head. Provide an API - retry_lockup_detector_init() for anyone who needs to delayed init lockup detector. The original assumption is: nobody should use delayed probe after lockup_detector_check() (which has __init attribute). That is, anyone uses this API must call between lockup_detector_init() and lockup_detector_check(), and the caller must have __init attribute The delayed init flow is: 1. lockup_detector_init() get -EBUSY from arch code, set allow_lockup_detector_init_retry=true 2. PMU arch code init done, call retry_lockup_detector_init(). 3. retry_lockup_detector_init() queue the work only when allow_lockup_detector_init_retry=true which means nobody should call this before lockup_detector_init(). 4. the work lockup_detector_delay_init() is doing without wait event. if probe success, set allow_lockup_detector_init_retry=false. 5. at late_initcall_sync(), lockup_detector_check() call flush_work() first to avoid previous retry_lockup_detector_init() is not scheduled. And then test whether allow_lockup_detector_init_retry is false, if it's true, means we have pending init un-finished, than forcely queue work again and flush_work to make sure the __init section won't be freed before the work done. [1] https://lore.kernel.org/lkml/20211014024155.15253-1-kernelfans@gmail.com/ v3: 1. Tweak commit message in patch 04 2. Remove wait event 3. s/lockup_detector_pending_init/allow_lockup_detector_init_retry/ 4. provide api retry_lockup_detector_init() v2: 1. Tweak commit message in patch 01/02/04/05 2. Remove vobose WARN in patch 04 within watchdog core. 3. Change from three states variable: detector_delay_init_state to two states variable: allow_lockup_detector_init_retry Thanks Petr Mladek for the idea. > 1. lockup_detector_work() called before lockup_detector_check(). > In this case, wait_event() will wait until lockup_detector_check() > clears detector_delay_pending_init and calls wake_up(). > 2. lockup_detector_check() called before lockup_detector_work(). > In this case, wait_even() will immediately continue because > it will see cleared detector_delay_pending_init. 4. Add comment in code in patch 04/05 for two states variable changing. https://lore.kernel.org/lkml/20220307154729.13477-1-lecopzer.chen@mediatek.com/ Lecopzer Chen (4): kernel/watchdog: remove WATCHDOG_DEFAULT kernel/watchdog: change watchdog_nmi_enable() to void kernel/watchdog: Adapt the watchdog_hld interface for async model arm64: Enable perf events based hard lockup detector Pingfan Liu (1): kernel/watchdog_hld: Ensure CPU-bound context when creating hardlockup detector event arch/arm64/Kconfig | 2 + arch/arm64/kernel/Makefile | 1 + arch/arm64/kernel/perf_event.c | 12 +++++- arch/sparc/kernel/nmi.c | 8 ++-- drivers/perf/arm_pmu.c | 5 +++ include/linux/nmi.h | 5 ++- include/linux/perf/arm_pmu.h | 2 + kernel/watchdog.c | 67 +++++++++++++++++++++++++++++++--- kernel/watchdog_hld.c | 8 +++- 9 files changed, 95 insertions(+), 15 deletions(-) -- 2.25.1