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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C4E4BCCF9F8 for ; Wed, 5 Nov 2025 21:07:54 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 304888E002D; Wed, 5 Nov 2025 16:07:54 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2DBD38E0002; Wed, 5 Nov 2025 16:07:54 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1F1E68E002D; Wed, 5 Nov 2025 16:07:54 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 0F48B8E0002 for ; Wed, 5 Nov 2025 16:07:54 -0500 (EST) Received: from smtpin03.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id BD4995916B for ; Wed, 5 Nov 2025 21:07:53 +0000 (UTC) X-FDA: 84077790426.03.69C4911 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf10.hostedemail.com (Postfix) with ESMTP id 40AB8C000F for ; Wed, 5 Nov 2025 21:07:52 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uqBh1peA; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of frederic@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=frederic@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1762376872; a=rsa-sha256; cv=none; b=4kt5qjBRCfIf+lUPXwb2lPF+vRFX7wjooSEIdtvvQtcjodfUgkcnlYr6zSAmiR2/4epA4/ AG82c+O7J1mXdsGAJZlN8EUoNNT+PbqBi133Z9F+StWt2wQV5n0ngnj2Q20T0wVNI0ZrKR 5cnhZBaR1xTeBVbOtGl7SeOGD9Szjm4= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=uqBh1peA; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of frederic@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=frederic@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1762376872; 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-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=f8fhvEoEt0tjcERWsEExVHDVeWMefORFMihOatSLeuc=; b=tD/c12Ki5Db5+GPkLgOm0IGW7Ooq6pEwlLqDfPJqLdTV7KaR5umicpP6wCArXQ+WlquUo4 9NdDir/Gm9AgOA2ftLqvZRiPNgQvohGTlcUY6Jfd3CJHJaGEgT40uJzDlQTptlTsYdFWLV LJzNSMtUOCy2HiCbUPA3s+gAqBC4i7s= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 534AC40898; Wed, 5 Nov 2025 21:07:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEAB4C4CEF5; Wed, 5 Nov 2025 21:07:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762376871; bh=ZcOaIdyFvlxFsz4x9bV8dX/urbiaQ2dIYf+IOrGWyKQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uqBh1peA3OwqS5304aC8e215GChgjNQ+xz8WZIQjvhmtUS6f7nqh/RdQVeNQ2M1h0 N9H3k5WiLHpEb6YnuD/MWiQNlkqvtuYe7W0HDhMHx5X8eNFG6DBGHNKHlJoU2BaZ3M rY4SVKr9xZY+z9hsVZG9KG/MPb2rofpyd5Vsybfo7AU5hqZEdZTrlKKYfGBaIM7drb 2RHucdD91Kljr+Sb2WKdMpyTxwAtuFcHF2KllXdzXz5owrbsFGBYFYh+LObYkRbxKp 6VQgFGT1HY05dsL5fIdD8y7aTR9kXshC2UmQ59+mAygTcfny0kDhWu6JYvJ0+oQUt1 C3W1zYUxNI9Ng== From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Andrew Morton , Bjorn Helgaas , Catalin Marinas , Danilo Krummrich , "David S . Miller" , Eric Dumazet , Gabriele Monaco , Greg Kroah-Hartman , Ingo Molnar , Jakub Kicinski , Jens Axboe , Johannes Weiner , Lai Jiangshan , Marco Crivellari , Michal Hocko , Muchun Song , Paolo Abeni , Peter Zijlstra , Phil Auld , "Rafael J . Wysocki" , Roman Gushchin , Shakeel Butt , Simon Horman , Tejun Heo , Thomas Gleixner , Vlastimil Babka , Waiman Long , Will Deacon , cgroups@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-pci@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH 29/31] kthread: Comment on the purpose and placement of kthread_affine_node() call Date: Wed, 5 Nov 2025 22:03:45 +0100 Message-ID: <20251105210348.35256-30-frederic@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251105210348.35256-1-frederic@kernel.org> References: <20251105210348.35256-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 40AB8C000F X-Stat-Signature: udkczn1egw4two8ufhjukt9wdbwcs46m X-HE-Tag: 1762376872-69951 X-HE-Meta: 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 Beeu+wsd /QuMxgwDT9fJcCF4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: It may not appear obvious why kthread_affine_node() is not called before the kthread creation completion instead of after the first wake-up. The reason is that kthread_affine_node() applies a default affinity behaviour that only takes place if no affinity preference have already been passed by the kthread creation call site. Add a comment to clarify that. Reported-by: Peter Zijlstra Signed-off-by: Frederic Weisbecker --- kernel/kthread.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/kthread.c b/kernel/kthread.c index f535d4e66a71..e38ff9b943cf 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -453,6 +453,10 @@ static int kthread(void *_create) self->started = 1; + /* + * Apply default node affinity if no call to kthread_bind[_mask]() nor + * kthread_affine_preferred() was issued before the first wake-up. + */ if (!(current->flags & PF_NO_SETAFFINITY) && !self->preferred_affinity) kthread_affine_node(); -- 2.51.0