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 86757C0032E for ; Wed, 25 Oct 2023 21:35:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9D3476B031D; Wed, 25 Oct 2023 17:35:45 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 983476B0322; Wed, 25 Oct 2023 17:35:45 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 84A7C6B0326; Wed, 25 Oct 2023 17:35:45 -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 731AD6B031D for ; Wed, 25 Oct 2023 17:35:45 -0400 (EDT) Received: from smtpin10.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 4C9C71A0772 for ; Wed, 25 Oct 2023 21:35:45 +0000 (UTC) X-FDA: 81385291050.10.2546366 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf30.hostedemail.com (Postfix) with ESMTP id 7A2038001C for ; Wed, 25 Oct 2023 21:35:43 +0000 (UTC) Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=gvc31YCp; dmarc=none; spf=pass (imf30.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1698269743; a=rsa-sha256; cv=none; b=HJwDCyuHm4XlwasFsQdZlo0YB/17m0gA93rfIkDEH55FmnPOZY5dZQrHpp3+mSUPAee7aT EXCahYD21Jc7f0Vm26D8MbKXZbiBcQQAwLe5+pGQnXaQeHbgEhC3CQhai/B26NOKO+QoV9 Bb5nS/tGrK3dj8VrehWqpx3XxPF5Y0U= ARC-Authentication-Results: i=1; imf30.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=gvc31YCp; dmarc=none; spf=pass (imf30.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1698269743; 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=nsQUs9HpmqqONjSFfSfNK05Cw8v+f+5EPyvVkDrlURM=; b=2l3Lcz0MnzXEnqiO4YOqOdamnu6jF7tUSFr2k9uNV00vrRdTFHRadXBJnEhK2+GiAJ8L8U 2T6w/XXXAPmuUyxzbxELt62chRN24aZAz2HzETW7sUSZSGEsQsKAuY/HMSGSnmgOWSBIDV s6W4muD3lD/ider8hgErpiEZxxlPWyo= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 81FAE623B8; Wed, 25 Oct 2023 21:35:42 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEE8FC433C8; Wed, 25 Oct 2023 21:35:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1698269742; bh=IS28A/VyLk5I38SKgMfcQn09iILXb887HXHzcLznG8g=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=gvc31YCpv+Y7y0YjUqk94gbhBtUUU0P1IMbjAwMKx6kH8R/tWBMgC+N4v3FSdU2sv 9x94CASS+zC889ij66qaaceSvGl7tDRXGSUEfEiu9QknBLeB08+2AUo46wlN2I/q2P FpKJIh/hiRpGDm//nPazoePJ4cqxZ5bb57RftGCs= Date: Wed, 25 Oct 2023 14:35:41 -0700 From: Andrew Morton To: Charan Teja Kalla Cc: Pavan Kondeti , , , , , , , , Subject: Re: [PATCH] mm/sparsemem: fix race in accessing memory_section->usage Message-Id: <20231025143541.e7cf114239b84105711a5f70@linux-foundation.org> In-Reply-To: References: <1697202267-23600-1-git-send-email-quic_charante@quicinc.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 7A2038001C X-Stat-Signature: c57udia95zpjf95dm8cm68xmmohdbpdi X-HE-Tag: 1698269743-715702 X-HE-Meta: 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 jPWZMf3F JIkJlJOZmy/hyWfp4XnqWBUIKzIC9QAMYpZw2/2IHYXX5FH1B6jKMHIK2NmrdCqMp1klwVUkr2DGiFqXIiw0E16MAoFiQeuWVTJi/5q7IxDvd4h5QkjNTr+ogpXzVYNrNj9+V0kUDS/LTwrgoTJNhWIv/ToIwmZ4Pyq6WjtjlqRBMtRBtco5OqRgglD8zGWlFI9KRXKf2kLXGZbbNLX74NiSgJXR7fJ7m4NofMfHWcieFkg/35K0J9wSq+nw8CZOcWo5oDs3TGtEpJpOgNkwd1sJ5SdnfJHLJwM9iU9Wz7CoxwoHBim7czqvw+ckPMau+2fmStfBKGFkh5MiQygBfAuTPu7Py909Kxshb0WwUGqKXpLc= 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: On Tue, 17 Oct 2023 19:40:15 +0530 Charan Teja Kalla wrote: > >> * was allocated during boot. > >> */ > >> if (!PageReserved(virt_to_page(ms->usage))) { > >> + synchronize_rcu(); > >> kfree(ms->usage); > >> ms->usage = NULL; > >> } > > If we add NULL checks around ms->usage, this becomes > > > > tmp = rcu_replace_pointer(ms->usage, NULL, hotplug_locked()); > > syncrhonize_rcu(); > > kfree(tmp); > Per David input, I am working on using kfree_rcu(). How's it coming along? Given that we're at 6.6-rc7 and given that this issue is causing daily crashes in your device farm, I'm thinking that we use the current version of your patch for 6.6 and for -stable. We can look at the kfree_rcu() optimization for later kernel releases?