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 11BF9F8D74B for ; Thu, 16 Apr 2026 14:35:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 38FBA6B0005; Thu, 16 Apr 2026 10:35:20 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3671D6B0089; Thu, 16 Apr 2026 10:35:20 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 27D8B6B008A; Thu, 16 Apr 2026 10:35:20 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 180ED6B0005 for ; Thu, 16 Apr 2026 10:35:20 -0400 (EDT) Received: from smtpin13.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id C36FB1B8C7F for ; Thu, 16 Apr 2026 14:35:19 +0000 (UTC) X-FDA: 84664666758.13.5F6F6D0 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf03.hostedemail.com (Postfix) with ESMTP id EB12D20003 for ; Thu, 16 Apr 2026 14:35:17 +0000 (UTC) Authentication-Results: imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=IAEt9ZhW; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf03.hostedemail.com: domain of harry@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=harry@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1776350118; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=AHjwqREaX4olKNBTjGOGV1Zd7tIlqt0km+88j1qh1ME=; b=ucCY5lMP3nu/YTNKKwnjaRUPaWvGUsI22OAF+QCfrjNuJ2f4tzecgwMl0cFVHRPbxrbf2n T03QFAhHRMOkn4A9NA1QXejT8LkRkrDnw6N4ThmSim8l7qU75DuMzodqLo8fItGe6kzPkK sGzfn5MnmMJ/IVYgBRuEAb2hnE7Kvh4= ARC-Authentication-Results: i=1; imf03.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=IAEt9ZhW; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf03.hostedemail.com: domain of harry@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=harry@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1776350118; a=rsa-sha256; cv=none; b=z1jkYIebZcSO2hdP+wUJBM9Nj9q0v60tp6t8GJSFqDqpUrhUG5NtnFguXpPb7DX6SPJnSi NYDVxGNqPzalim6ftTKbuF9D9URQTjPohKomjwe4qO85PQmjmsToxdM59BImEJGL0F9Lwo eFgZjuf0/m51cZy4WOH78TsNwUMnqM8= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id DA665436FE; Thu, 16 Apr 2026 14:35:16 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B4F2C2BCAF; Thu, 16 Apr 2026 14:35:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776350116; bh=cogrMzgZEQxM7xPhwtdnRLBHYY01WZA4ogqqstyhGZk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=IAEt9ZhW7IbIrs+qOCzY7b4TRDQln0yB06rerpru/HkeEmABN4EJA7eGnduu8N1Qx 66RmTLZwL6wiWz15bQUnOqTcH94svcNq9mSumPdoKZJdbMwgL7KdmK7iaAKnaZTCkb BNVHE/Mx7/eNy5llnau+nvky+W1GGUJPV3XfakxHM3q9UZqAVDdA/a9HAA9KfmHkJZ 8zJefhxu7ohSv/ZXzX2BRq3RXRuWnZZrBDVOAZF6JRbrA1DuKTM15SW9T2JGmQF1Ti g+FAD8z6yi5tIafKKCbmCxOgNUEKB8Ue08j/XSSghXGDuPXC+9rD63PKXOaRLe8j5H N6dzSUjkzHmFg== Date: Thu, 16 Apr 2026 23:35:14 +0900 From: "Harry Yoo (Oracle)" To: Alexei Starovoitov Cc: "Vlastimil Babka (SUSE)" , Matthew Wilcox , Vlastimil Babka , Peter Zijlstra , Ingo Molnar , Will Deacon , Sebastian Andrzej Siewior , LKML , "linux-mm@kvack.org" , Linus Torvalds , Waiman Long , Mel Gorman , Steven Rostedt , Hao Li , Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Christoph Lameter , David Rientjes , Roman Gushchin Subject: Re: [RFC] making nested spin_trylock() work on UP? Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: EB12D20003 X-Stat-Signature: qozb7znn8kxc9m1b5ok3pfx7fpgxxqt1 X-Rspam-User: X-HE-Tag: 1776350117-119383 X-HE-Meta: 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 5m3iYQ6S MxFVT8q+dyUOzTEuF0QFqdq8Ayf1exfsdOOuSfMVw4mkyZPtsNK/BwMpDQfY2JiIO8Ye3kjMZ1yXpVGiVnvHQiIA7Z0LhTbYUgBVUg0HXlavxarwqNlnzABYz4LHiMMchT5nKDJSzeRZ8ziKfZ8OzdRR8JkuGQRl4XBKINX0f9pC055nJTlbezKphF0UQkIEm7XD5ahlJ9DbiaGwJGZyESCbYfO3fOuoypi8oQB+x+D3c1/vGZjKeJ/s5a0t1eEAUaRQeNQAcNvOEMqaEP/RjweVsxKiBD/5pGNxnIMig1+5eKrNmBdmit/GRh9mOmDebPIT/G70KdrIcVrP8Vy+mQ3Ik4sV72dzx2qAQFAgTvkfoXQt9GN5VTAXwBqD9SNyCXEdwzkqX03fmigIUF8Hy8Yv74QwnGHGX9sJVOMGJk1Zh+sbAhxAv9jSJXT81/m1MkaoFxTX/YiAkSQdXHUDDPbVCsenxrxnpI0xX Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Apr 16, 2026 at 07:26:36AM -0700, Alexei Starovoitov wrote: > On Thu Apr 16, 2026 at 3:05 AM PDT, Vlastimil Babka (SUSE) wrote: > >> I think we need a special spinlock type that wraps something like this > >> and use them when spinlocks can be trylock'd in an unknown context: > >> pcp lock, zone lock, per-node partial slab list lock, > >> per-node barn lock, etc. > > > > Soudns like a lot of hassle for a niche config (SMP=n) where nobody would > > use e.g. bpf tracing anyway. We already have this in kmalloc_nolock(): > > > > /* > > * See the comment for the same check in > > * alloc_frozen_pages_nolock_noprof() > > */ > > if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) > > return NULL; > > > > It would be trivial to extend this to !SMP. However it wouldn't cover the > > kprobe context. Any idea Alexei? I think Vlastimil meant it'd be trivial to do: if ((IS_ENABLED(CONFIG_PREEMPT_RT) || !IS_ENABLED(CONFIG_SMP)) && (in_nmi() || in_hardirq())) return NULL; But it doesn't cover the case where kprobe hooks an arbitrary function (in the middle of kmalloc() or kfree()) and calls kmalloc_nolock()? > Yeah. Totally fine with that. So I'm confused exactly what you're fine with. Did you mean this? if (!IS_ENABLED(CONFIG_SMP) || (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq()))) return NULL; Or am I missing something? -- Cheers, Harry / Hyeonggon