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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7B59AC021AA for ; Thu, 20 Feb 2025 01:36:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1441D4401B6; Wed, 19 Feb 2025 20:36:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 0F48D4401AE; Wed, 19 Feb 2025 20:36:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EFE3A4401B6; Wed, 19 Feb 2025 20:36:23 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id D38614401AE for ; Wed, 19 Feb 2025 20:36:23 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 5DF0AB1945 for ; Thu, 20 Feb 2025 01:36:23 +0000 (UTC) X-FDA: 83138607846.04.0EC0063 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf12.hostedemail.com (Postfix) with ESMTP id EF8C340006 for ; Thu, 20 Feb 2025 01:36:20 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="J9t8+mu/"; spf=pass (imf12.hostedemail.com: domain of llong@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=llong@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1740015381; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=Dyt+UyexCy2S6NSt7d7+7qR1hd7bun67cNPljmVUdxA=; b=jUVWWRNMOcZJ+XTje8DM6rbqlrtNmSqwbcFdICpJiPP5c23NXwdOWX7BWWv4ZaugCeZXy2 v03cQrkQ2Kava4ciy12QTo0WSVOvFwSrUYe3gdzkCzoAydEhfLvTMDCvvhLoJHH++BGiQE a3Cnrd+PdFSJ+HxzyPj6XdKu7C3DNbw= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b="J9t8+mu/"; spf=pass (imf12.hostedemail.com: domain of llong@redhat.com designates 170.10.129.124 as permitted sender) smtp.mailfrom=llong@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1740015381; a=rsa-sha256; cv=none; b=JB4yWHKn7p105Fn2KGSRvLJDXOtVI1VwjclgXcApu0Itupd1pCj3zNCFOkzktZRjII4gmi w2Z4eQ/RjiwenEoCuypqAFLNJrJ5Tkp2YzthCAsP6ps1vANpkOE4KQjofsVOSE6Yl4kr9q v/ZZrVJmeu09Gi2BrjNX1gdVWImvSRI= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1740015380; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=Dyt+UyexCy2S6NSt7d7+7qR1hd7bun67cNPljmVUdxA=; b=J9t8+mu/5BOmK6HrivX7UBXqPR5SfT5hGxMRGs3ngmAj+wfmuJ/yyJAUBg/wA7LTNwO/tW +5CVIge5JtDgmuE0UhxcQZBqU1EvUjGzjC51z+cx5iFniNxL3LMozf0+eXNbvSHdR2x/M2 8vRU/dCpj3NLRZFZUjpcAQrAZqZniBQ= Received: from mail-oa1-f69.google.com (mail-oa1-f69.google.com [209.85.160.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-13-0nyxe7PCPlu-XeUnS7Y1ug-1; Wed, 19 Feb 2025 20:36:17 -0500 X-MC-Unique: 0nyxe7PCPlu-XeUnS7Y1ug-1 X-Mimecast-MFC-AGG-ID: 0nyxe7PCPlu-XeUnS7Y1ug_1740015376 Received: by mail-oa1-f69.google.com with SMTP id 586e51a60fabf-2bcf138c13dso475301fac.0 for ; Wed, 19 Feb 2025 17:36:16 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1740015376; x=1740620176; h=content-transfer-encoding:in-reply-to:content-language:references :cc:to:subject:user-agent:mime-version:date:message-id:from :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Dyt+UyexCy2S6NSt7d7+7qR1hd7bun67cNPljmVUdxA=; b=xIexikm5KXCa/8GwQZlEn+9R//CORMu354OHPNFdhQlMdhMM9Dwyai5QVBTlsscr8w EKulMvYyNdHJ4d2CrxE3dou6fI7s52zZWqSNf+KtLf1v0ln+4YjGA39tCzgIhUAN8cAc AXUzUmS18uXBktPD/zVcNqFc+VEG/u92bZvDQeB2DJgjwy+/hkswK1f2xQn7uIrqaPEH Qci0OPztK1ePsnwC33Y0VwEA+qvafTnZuDVywrqfb5KbS7J25iTcQsw/YUvFzKjAwhxP h3O3coQIxfbI466pi8lSSDh/hNzrF7EudiJZzEJXlTRwYXtJFYEs3f3XyubIKDQjwn7u hmTg== X-Forwarded-Encrypted: i=1; AJvYcCV3d3W9aro3aWSx6P9zjt6aqzQu9YPnboX66/AcnphpHBHTYmCwwfVF7iwh6MlxczKeBFletFtAJA==@kvack.org X-Gm-Message-State: AOJu0Yy8ZX4H4aCEqVd+ZByD2qtTaJLLvuoQy6rukiBvfiuyagxJCLIB gsZrcFVHr82a3qeuCRCkHc6XbSkJvye73ybR2VGrozfg0kuP7QAEFttHu2LjgkBnoz3hP3ULt2i h0/8EBPwGW7+uGXZ9w1d7ZWuLiNEJVgH0Gfrb+62bbqESv7e8 X-Gm-Gg: ASbGncuHbgVnat3aHF5BjY+IAZXXgQMkNax+nS77DycNIv4zI3XOzkMq2e3oVAvdjuK 25z7sFpKd0M3RvKbmfXdiPXl6sIzb5LejnLEG8u4cVS9OQy//KMUgYveQCJT3kiqGZ/jIcflPBx 3VyIw0TIRV5LlzyY5b1ijiRf4TVl5IfGOCXYMoY6uxdmLZuVHIQG4TqH5kufsa7R9dahSNQCLlj YakoluvGumCpAua6iuqE4OMFREr5QQTZmPjz3P4rzDG44lGgYJ1WpW0DPtJZlJg4shQ3d1nAHlI IlsjHyNyiBLmZaaDYFUxpw1FSQo1PGKDWNhCrkQ9XeI7PvlJ X-Received: by 2002:a05:6871:6ac:b0:29f:8a1b:f76b with SMTP id 586e51a60fabf-2bc99a93119mr14390395fac.9.1740015376273; Wed, 19 Feb 2025 17:36:16 -0800 (PST) X-Google-Smtp-Source: AGHT+IEc3qdhIgt6MllXMs8VtuUxscrVHayzDGAXSY9S4MfEFS3lGK7gLdXU7IIbu3ceV0bvAY3SAQ== X-Received: by 2002:a05:6871:6ac:b0:29f:8a1b:f76b with SMTP id 586e51a60fabf-2bc99a93119mr14390384fac.9.1740015375998; Wed, 19 Feb 2025 17:36:15 -0800 (PST) Received: from ?IPV6:2601:188:c100:5710:627d:9ff:fe85:9ade? ([2601:188:c100:5710:627d:9ff:fe85:9ade]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7272fb6eb19sm1559968a34.27.2025.02.19.17.36.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 19 Feb 2025 17:36:15 -0800 (PST) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: Date: Wed, 19 Feb 2025 20:36:13 -0500 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung on mutex To: "Masami Hiramatsu (Google)" , Waiman Long Cc: Steven Rostedt , Peter Zijlstra , Ingo Molnar , Will Deacon , Andrew Morton , Boqun Feng , Joel Granados , Anna Schumaker , Lance Yang , Kent Overstreet , Yongliang Gao , Tomasz Figa , Sergey Senozhatsky , linux-kernel@vger.kernel.org, Linux Memory Management List References: <173997003868.2137198.9462617208992136056.stgit@mhiramat.tok.corp.google.com> <173997004932.2137198.7959507113210521328.stgit@mhiramat.tok.corp.google.com> <20250219112308.5d905680@gandalf.local.home> <0fa9dd8e-2d83-487e-bfb1-1f5d20cd9fe6@redhat.com> <20250219152435.35077ac3@gandalf.local.home> <20250220075639.298616eb494248d390417977@kernel.org> In-Reply-To: <20250220075639.298616eb494248d390417977@kernel.org> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: R-EzDn5HiZxlrjTGmPTwt8Bn1VBW-IfmtTU0J81i2ho_1740015376 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EF8C340006 X-Stat-Signature: cug6pn1apwfnmqt841xzd5ozqt16hpqk X-HE-Tag: 1740015380-576525 X-HE-Meta: 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 9qZRnX8S 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.003722, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2/19/25 5:56 PM, Masami Hiramatsu (Google) wrote: > On Wed, 19 Feb 2025 17:44:11 -0500 > Waiman Long wrote: > >> On 2/19/25 3:24 PM, Steven Rostedt wrote: >>> On Wed, 19 Feb 2025 15:18:57 -0500 >>> Waiman Long wrote: >>> >>>> It is tricky to access the mutex_waiter structure which is allocated >>>> from stack. So another way to work around this issue is to add a new >>>> blocked_on_mutex field in task_struct to directly point to relevant >>>> mutex. Yes, that increase the size of task_struct by 8 bytes, but it is >>>> a pretty large structure anyway. Using READ_ONCE/WRITE_ONCE() to access >>> And it's been on my TODO list for some time to try to make that structure >>> smaller again :-/ > I agree to add the field, actually it was my first prototype :) > >>>> this field, we don't need to take lock, though taking the wait_lock may >>>> still be needed to examine other information inside the mutex. > Do we need to take it just for accessing owner, which is in an atomic? Right. I forgot it is an atomic_long_t. In that case, no lock should be needed. Cheers, Longman