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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1ADC6C46470 for ; Wed, 8 Aug 2018 12:36:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BF60F219E6 for ; Wed, 8 Aug 2018 12:36:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BF60F219E6 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727055AbeHHO4C (ORCPT ); Wed, 8 Aug 2018 10:56:02 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:55927 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726733AbeHHO4B (ORCPT ); Wed, 8 Aug 2018 10:56:01 -0400 Received: from fsav303.sakura.ne.jp (fsav303.sakura.ne.jp [153.120.85.134]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w78CaN8k030668; Wed, 8 Aug 2018 21:36:23 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav303.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav303.sakura.ne.jp); Wed, 08 Aug 2018 21:36:23 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav303.sakura.ne.jp) Received: from [192.168.1.8] (softbank126074194044.bbtec.net [126.74.194.44]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w78CaJr4030649 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 8 Aug 2018 21:36:22 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH RFC 02/10] mm: Make shrink_slab() lockless To: Kirill Tkhai References: <153365347929.19074.12509495712735843805.stgit@localhost.localdomain> <153365626605.19074.16202958374930777592.stgit@localhost.localdomain> <591d2063-0511-103d-bef6-dd35f55afe32@virtuozzo.com> Cc: mhocko@suse.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org From: Tetsuo Handa Message-ID: Date: Wed, 8 Aug 2018 21:36:18 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <591d2063-0511-103d-bef6-dd35f55afe32@virtuozzo.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/08/08 20:51, Kirill Tkhai wrote: > @@ -192,7 +193,6 @@ static int prealloc_memcg_shrinker(struct shrinker *shrinker) > int id, ret = -ENOMEM; > > down_write(&shrinker_rwsem); > - /* This may call shrinker, so it must use down_read_trylock() */ > id = idr_alloc(&shrinker_idr, SHRINKER_REGISTERING, 0, 0, GFP_KERNEL); > if (id < 0) > goto unlock; I don't know why perf reports down_read_trylock(&shrinker_rwsem). But above code is already bad. GFP_KERNEL allocation involves shrinkers and the OOM killer would be invoked because shrinkers are defunctional due to this down_write(&shrinker_rwsem). Please avoid blocking memory allocation with shrinker_rwsem held.