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 5EDF7C6FD19 for ; Mon, 6 Mar 2023 17:53:20 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id E63B36B0071; Mon, 6 Mar 2023 12:53:19 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E14316B0072; Mon, 6 Mar 2023 12:53:19 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D03746B0073; Mon, 6 Mar 2023 12:53:19 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id C07A46B0071 for ; Mon, 6 Mar 2023 12:53:19 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 6A2E11408BC for ; Mon, 6 Mar 2023 17:53:19 +0000 (UTC) X-FDA: 80539220118.23.8F4524E Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf10.hostedemail.com (Postfix) with ESMTP id A621EC001F for ; Mon, 6 Mar 2023 17:53:17 +0000 (UTC) Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=jwHB7kNZ; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf10.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1678125197; 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=C1hwoiYmIzjyFk8ZALc5sULe62pU2P1ms/hhtGj0y1k=; b=TNX/a7nNrnIG3mAkHKNeJ9jhOjlmhn9rd4leM7Tkd4HLIvLrtyjgbYVhbsA01ltZfFCOcd HKQxr6WlvdyUQ6krcIDk/7Uw0//dGGsbs4gICHNDXfCFuxG6Ovndota3asVIr+LYQ+xEGi tBZGdjNHzIZ2Z6rCufrLKpZNVtkhf3M= ARC-Authentication-Results: i=1; imf10.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=jwHB7kNZ; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf10.hostedemail.com: domain of mhocko@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=mhocko@suse.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1678125197; a=rsa-sha256; cv=none; b=M1h1AvLrfpzP/Pu/VzTiBWjdGkhAajWwcRPEcJO7kmaGDjUPiCf9KjZby7RBfiV2UF2pab jbCL/rktnuMW6msuWDLxrR2zE0rn9Ui0aFo0BZzT20eigDuSWMflHdjfGzo/8M+xRYB/pr XIsnyCoRCUneiSvTduv92vXkpu0kvzM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 5A5DD1FDED; Mon, 6 Mar 2023 17:53:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1678125196; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=C1hwoiYmIzjyFk8ZALc5sULe62pU2P1ms/hhtGj0y1k=; b=jwHB7kNZdVMu7pORMKiDgDdWZI0fuRoEnFOqAwGt0mE6k4eAt5T1x+raVUsiRb0qyU9riW /SXi4S4tVqanqOvQoom/OxpX4HBsaGCkjfQqJxpcVgINgSZL+rhxKWmFU8fDVzgu1acaMV /jN2VHcmUYjvKvHqXSsbaYb3PY9Heng= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 3B50813513; Mon, 6 Mar 2023 17:53:16 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 6U3zC4woBmTgfwAAMHmgww (envelope-from ); Mon, 06 Mar 2023 17:53:16 +0000 Date: Mon, 6 Mar 2023 18:53:15 +0100 From: Michal Hocko To: Yue Zhao Cc: akpm@linux-foundation.org, roman.gushchin@linux.dev, hannes@cmpxchg.org, shakeelb@google.com, muchun.song@linux.dev, willy@infradead.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, tangyeechou@gmail.com Subject: Re: [PATCH v2, 3/4] mm, memcg: Prevent memory.oom_control load/store tearing Message-ID: References: <20230306154138.3775-1-findns94@gmail.com> <20230306154138.3775-4-findns94@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230306154138.3775-4-findns94@gmail.com> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A621EC001F X-Stat-Signature: rh57f6rokarkph869kbxsenztjk8sisr X-HE-Tag: 1678125197-879463 X-HE-Meta: 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 R3ru9KyS U+zLkvJX3ag1e/IDcRpGHqG5OO+UpaSWHy59pwTlrm2uaw9fGfjR3uizMCKXAjXAggilcJUz/xWPWUCped3XiRdX8yXwl8zXft+NQimRkfaznlHqIeEfs4L9RQnnckGHxpSAmsv8c2qlcWE8P5HSrhSnW2FHW5MHpSdaXXGxu83rq1Y/nSaZh7SohBiE6h7P5GOJc9YUCu6RxWT+zAL6eGRyLxtquBmXyER/OhOXYlgOSYqw= 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: On Mon 06-03-23 23:41:37, Yue Zhao wrote: > The knob for cgroup v1 memory controller: memory.oom_control > is not protected by any locking so it can be modified while it is used. > This is not an actual problem because races are unlikely. > But it is better to use READ_ONCE/WRITE_ONCE to prevent compiler from > doing anything funky. > > The access of memcg->oom_kill_disable is lockless, > so it can be concurrently set at the same time as we are > trying to read it. > > Signed-off-by: Yue Zhao > --- > mm/memcontrol.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index dca895c66a9b..26605b2f51b1 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -4515,7 +4515,7 @@ static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v) > { > struct mem_cgroup *memcg = mem_cgroup_from_seq(sf); > > - seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable); > + seq_printf(sf, "oom_kill_disable %d\n", READ_ONCE(memcg->oom_kill_disable)); > seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom); > seq_printf(sf, "oom_kill %lu\n", > atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL])); > @@ -4531,7 +4531,7 @@ static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css, > if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1))) > return -EINVAL; > > - memcg->oom_kill_disable = val; > + WRITE_ONCE(memcg->oom_kill_disable, val); > if (!val) > memcg_oom_recover(memcg); Any specific reasons you haven't covered other accesses (mem_cgroup_css_alloc, mem_cgroup_oom, mem_cgroup_oom_synchronize)? > > -- > 2.17.1 -- Michal Hocko SUSE Labs