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 X-Spam-Level: X-Spam-Status: No, score=-7.6 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD57BC433FE for ; Fri, 10 Sep 2021 07:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C0B8F60FC0 for ; Fri, 10 Sep 2021 07:59:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231671AbhIJIA7 (ORCPT ); Fri, 10 Sep 2021 04:00:59 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:9412 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231502AbhIJIA6 (ORCPT ); Fri, 10 Sep 2021 04:00:58 -0400 Received: from dggemv704-chm.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4H5Spg0MfRz8yG8; Fri, 10 Sep 2021 15:55:23 +0800 (CST) Received: from dggpemm500001.china.huawei.com (7.185.36.107) by dggemv704-chm.china.huawei.com (10.3.19.47) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Fri, 10 Sep 2021 15:59:44 +0800 Received: from [10.174.177.243] (10.174.177.243) by dggpemm500001.china.huawei.com (7.185.36.107) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.8; Fri, 10 Sep 2021 15:59:44 +0800 Subject: Re: [BUG] amba: Remove deferred device addition To: Saravana Kannan CC: Rob Herring , "linux-kernel@vger.kernel.org" , Frank Rowand , , Russell King , "Linus Walleij" , linux-arm-kernel , Dmitry Torokhov , References: <20210816074619.177383-1-wangkefeng.wang@huawei.com> <20210816074619.177383-4-wangkefeng.wang@huawei.com> <85b28900-5f42-b997-2ded-0b952bc2a03e@huawei.com> <265bb783-10da-a7c1-2625-055dec5643a3@huawei.com> From: Kefeng Wang Message-ID: <4a8b0a6d-b1d5-ffe9-8e31-61844cb9bd89@huawei.com> Date: Fri, 10 Sep 2021 15:59:43 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/9/9 11:30, Saravana Kannan wrote: > On Fri, Aug 27, 2021 at 6:09 PM Kefeng Wang wrote: >> >> On 2021/8/28 3:09, Saravana Kannan wrote: >>> On Fri, Aug 27, 2021 at 7:38 AM Kefeng Wang wrote: >>>> On 2021/8/27 8:04, Saravana Kannan wrote: >>>>> On Thu, Aug 26, 2021 at 1:22 AM Kefeng Wang wrote: >>>>>>>>> Btw, I've been working on [1] cleaning up the one-off deferred probe >>>>>>>>> solution that we have for amba devices. That causes a bunch of other >>>>>>>>> headaches. Your patch 3/3 takes us further in the wrong direction by >>>>>>>>> adding more reasons for delaying the addition of the device. >>>>>> Hi Saravana, I try the link[1], but with it, there is a crash when boot >>>>>> (qemu-system-arm -M vexpress-a15), >>> I'm assuming it's this one? >>> arch/arm/boot/dts/vexpress-v2p-ca15_a7.dts >> I use arch/arm/boot/dts/vexpress-v2p-ca15-tc1.dts. >> >> qemu-system-arm -M vexpress-a15 -dtb vexpress-v2p-ca15-tc1.dtb -cpu >> cortex-a15 -smp 2 -m size=3G -kernel zImage -rtc base=localtime -initrd >> initrd-arm32 -append 'console=ttyAMA0 cma=0 kfence.sample_interval=0 >> earlyprintk debug ' -device virtio-net-device,netdev=net8 -netdev >> type=tap,id=net8,script=/etc/qemu-ifup,downscript=/etc/qemu-ifdown >> -nographic >> >>>>> Hi, >>>>> >>>>> It's hard to make sense of the logs. Looks like two different threads >>>>> might be printing to the log at the same time? Can you please enable >>>>> the config that prints the thread ID (forgot what it's called) and >>>>> collect this again? With what I could tell the crash seems to be >>>>> happening somewhere in platform_match(), but that's not related to >>>>> this patch at all? >>>> Can you reproduce it? it is very likely related(without your patch, the >>>> boot is fine), >>> Sorry, I haven't ever setup qemu and booted vexpress. Thanks for your help. >>> >>>> the NULL ptr is about serio, it is registed from amba driver. >>>> >>>> ambakmi_driver_init >>>> >>>> -- amba_kmi_probe >>>> >>>> -- __serio_register_port >>> Thanks for the pointer. I took a look at the logs and the code. It's >>> very strange. As you can see from the backtrace, platform_match() is >>> being called for the device_add() from serio_handle_event(). But the >>> device that gets added there is on the serio_bus which obviously >>> should be using the serio_bus_match. >> Yes, I am confused too. >>>> +Dmitry and input maillist, is there some known issue about serio ? >>>> >>>> I add some debug, the full log is attached. >>>> >>>> [ 2.958355][ T41] input: AT Raw Set 2 keyboard as >>>> /devices/platform/bus@8000000/bus@8000000:motherboard-bus/bus@8000000:motherboard-bus:iofpga-bus@300000000/1c060000.kmi/serio0/input/input0 >>>> [ 2.977441][ T41] serio serio1: pdev c1e05508, pdev->name (null), >>>> drv c1090fc0, drv->name vexpress-reset >>> Based on the logs you added, it's pretty clear we are getting to >>> platform_match(). It's also strange that the drv->name is >>> vexpress-reset >> ... >>>> [ 3.003113][ T41] Backtrace: >>>> [ 3.003451][ T41] [] (strcmp) from [] (platform_match+0xdc/0xf0) >>>> [ 3.003963][ T41] [] (platform_match) from [] (__device_attach_driver+0x3c/0xf4) >>>> [ 3.004769][ T41] [] (__device_attach_driver) from [] (bus_for_each_drv+0x68/0xc8) >>>> [ 3.005481][ T41] [] (bus_for_each_drv) from [] (__device_attach+0xf0/0x16c) >>>> [ 3.006152][ T41] [] (__device_attach) from [] (device_initial_probe+0x1c/0x20) >>>> [ 3.006853][ T41] [] (device_initial_probe) from [] (bus_probe_device+0x94/0x9c) >>>> [ 3.007259][ T41] [] (bus_probe_device) from [] (device_add+0x408/0x8b8) >>>> [ 3.007900][ T41] [] (device_add) from [] (serio_handle_event+0x1b8/0x234) >>>> [ 3.008824][ T41] [] (serio_handle_event) from [] (process_one_work+0x238/0x594) >>>> [ 3.009737][ T41] [] (process_one_work) from [] (worker_thread+0x5c/0x5f4) >>>> [ 3.010638][ T41] [] (worker_thread) from [] (kthread+0x178/0x194) >>>> [ 3.011496][ T41] [] (kthread) from [] (ret_from_fork+0x14/0x24) >>>> [ 3.011860][ T41] Exception stack(0xc1675fb0 to 0xc1675ff8) >>> But the platform_match() is happening for the device_add() from >>> serio_event_handle() that's adding a device to the serio_bus and it >>> should be using serio_bus_match(). >>> >>> I haven't reached any conclusion yet, but my current thought process >>> is that it's either: >>> 1. My patch is somehow causing list corruption. But I don't directly >>> touch any list in my change (other than deleting a list entirely), so >>> it's not clear how that would be happening. >> Maybe some concurrent driver load？ >> >>> 2. Without my patch, these AMBA device's probe would be delayed at >>> least until 5 seconds or possibly later. I'm wondering if my patch is >>> catching some bad timing assumptions in other code. >> After Rob's patch, It will retry soon. >> >> commit 039599c92d3b2e73689e8b6e519d653fd4770abb >> Author: Rob Herring >> Date: Wed Apr 29 15:58:12 2020 -0500 >> >> amba: Retry adding deferred devices at late_initcall >> >> If amba bus devices defer when adding, the amba bus code simply retries >> adding the devices every 5 seconds. This doesn't work well as it >> completely unsynchronized with starting the init process which can >> happen in less than 5 secs. Add a retry during late_initcall. If the >> amba devices are added, then deferred probe takes over. If the >> dependencies have not probed at this point, then there's no improvement >> over previous behavior. To completely solve this, we'd need to retry >> after every successful probe as deferred probe does. >> >> The list_empty() check now happens outside the mutex, but the mutex >> wasn't necessary in the first place. >> >> This needed to use deferred probe instead of fragile initcall ordering >> on 32-bit VExpress systems where the apb_pclk has a number of probe >> dependencies (vexpress-sysregs, vexpress-config). >> >> >>> You might be able to test out theory (2) by DEFERRED_DEVICE_TIMEOUT to >>> a much smaller number. Say 500ms or 100ms. If it doesn't crash, it >>> doesn't mean it's not (2), but if it does, then we know for sure it's >>> (2). >> ok, I will try this one, but due to above patch, it may not work. > Were you able to find anything more? I can't find any clue， and have no time to check this for now, is there any news from your side? > > -Saravana > . >