From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 58758265CC8; Tue, 1 Jul 2025 09:20:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.188 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751361659; cv=none; b=eEk9zUnPBo3mzAdRWznMBT0+YPWMPeyHTutB78Ss/dRMyNjSp7GtNFqr2MZjKz20rI4ox/qX9r+Wa8vAouvI6Kdm+F9dV/ozhxapmS/rn8n79FmY0jhKMBokTnZtNG81GIs43qjRf5J2/5rpx3N/OF2tVpimGp4kE2nxSffXgYM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1751361659; c=relaxed/simple; bh=P3XzVml8VOYHlwM4nPlymyPxhWlJy6Gon8cEG/DVKTk=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=iRMpuYEuD9nTxrlmAb2ooSBZig4XzIZtcWplrQpzRHlyT4Np9PptTf687G/ClPYahz/DH5twZkLVcKw2W8PzMVc78VYfrFMs9yjXpOy3cio1Kz0ynrbjcd+C8FfSnynWgHS/mnhua1PW7TJFC/6LdFrpE/PBXF5qN6Ul6ZDXuK0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.188 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.88.105]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4bWcpc59kdzWfv4; Tue, 1 Jul 2025 17:16:24 +0800 (CST) Received: from dggemv706-chm.china.huawei.com (unknown [10.3.19.33]) by mail.maildlp.com (Postfix) with ESMTPS id E15A51402CF; Tue, 1 Jul 2025 17:20:46 +0800 (CST) Received: from kwepemn200010.china.huawei.com (7.202.194.133) by dggemv706-chm.china.huawei.com (10.3.19.33) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 1 Jul 2025 17:20:46 +0800 Received: from [10.174.178.56] (10.174.178.56) by kwepemn200010.china.huawei.com (7.202.194.133) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Tue, 1 Jul 2025 17:20:45 +0800 Message-ID: <09e4d018-3db4-404e-a8f0-041cdee15a62@huawei.com> Date: Tue, 1 Jul 2025 17:20:45 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [QUESTION] problems report: rcu_read_unlock_special() called in irq_exit() causes dead loop To: Joel Fernandes , , "Xiongfeng Wang" CC: Joel Fernandes , , Frederic Weisbecker , Boqun Feng , , , , , "Wangshaobo (bobo)" , Xie XiuQi References: <9acd5f9f-6732-7701-6880-4b51190aa070@huawei.com> <3ce6f3ce-5dfb-8c59-cb7b-4619b70f8d25@huawei.com> <20250603185939.GA1109523@joelnvbox> <066e8121-c6c5-48ac-b35a-e6430d986dff@nvidia.com> Content-Language: en-GB From: Qi Xi In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To kwepemn200010.china.huawei.com (7.202.194.133) Hello everyone, Friendly ping about this problem :) Qi On 2025/6/6 2:56, Joel Fernandes wrote: > > On 6/4/2025 8:26 AM, Paul E. McKenney wrote: >>>>>>>> Or just don't send subsequent self-IPIs if we just sent one for the >>>>>>>> rdp. Chances are, if we did not get the scheduler's attention during >>>>>>>> the first one, we may not in subsequent ones I think. Plus we do send >>>>>>>> other IPIs already if the grace period was over extended (from the FQS >>>>>>>> loop), maybe we can tweak that? >>>>>>> Thanks a lot for your reply. I think it's hard for me to fix this issue as >>>>>>> above without introducing new bugs. I barely understand the RCU code. But I'm >>>>>>> very glad to help test if you have any code modifiction need to. I have >>>>>>> the VM and the syskaller benchmark which can reproduce the problem. >>>>>> Sure, I understand. This is already incredibly valuable so thank you again. >>>>>> Will request for your testing help soon. I also have a test module now which >>>>>> can sort-off reproduce this. Keep you posted! >>>>> Oh sorry I meant to ask - could you provide the full kernel log and also is >>>>> there a standalone reproducer syzcaller binary one can run to reproduce it in a VM? >>> Sorry, I communicate with the teams who maintain the syzkaller tools. He said >>> I can't send the syskaller binary out of the company. Sorry, but I can help to >>> reproduce. It's not complicate and not time consuming. >>> >>> I found the origin log which use kernel v6.6. But it's not complete. >>> Then I reprouce the problem using the latest kernel. >>> Both logs are attached as attachments. >>> >> Looking at both the v6.6 version and Joel's fix, I am forced to conclude >> that this bug has been there for a very long time. Thank you for your >> testing efforts and Joel for the fix! > Thanks. I am still working on polishing the fix Xiongfeng tested. I hope to have > it out next week for review. As we discussed I will split the context-tracking > API into a separate patch and will also add a separate documentation > comment-patch on why we need the irq_work. > > thanks, > > - Joel