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=-6.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 C9173C31E50 for ; Sun, 16 Jun 2019 15:14:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 6E7BD2084B for ; Sun, 16 Jun 2019 15:14:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6E7BD2084B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id D5F066B0005; Sun, 16 Jun 2019 11:14:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D0FAD8E0002; Sun, 16 Jun 2019 11:14:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id BD67A8E0001; Sun, 16 Jun 2019 11:14:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-ot1-f72.google.com (mail-ot1-f72.google.com [209.85.210.72]) by kanga.kvack.org (Postfix) with ESMTP id 952E86B0005 for ; Sun, 16 Jun 2019 11:14:36 -0400 (EDT) Received: by mail-ot1-f72.google.com with SMTP id f36so3674859otf.7 for ; Sun, 16 Jun 2019 08:14:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:from :to:cc:references:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=NYQJK/zo5XhCFiJZEOq4RoG1QrgP7TGctx8J6I5+Bw4=; b=Ra8wYfjdWwmyciU4Czu3oxpGpHM1ekamLZ5s9ISyi6yntIGP+xCYeJlkVn1+6zQO5t 5NofMUVP895SEnDZVyGcWArI65fAyTrfNn061QtHIJYa6nCOjEgfsK9eY4mkSydQG2ta z56rWd4CvlYOkkasdVqTLqGtJjniYMh0w005zV4BYGSqD+z42sTMHl6n5aawFMwCSI7N lwVIIU1vwmzBBkWg+27EzV0mC9nQrAc2mQf5ThkDIBl6YkzPSOVZeJX3gD6mk/OtS0hQ tSAzHunZUmFoT2x281bJENd+wYlX046fD9KnIJ1Mh2VkxLik0x9ae2pt1dyDBmMAx1U/ M41A== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp X-Gm-Message-State: APjAAAVMa28+UChhrjR+mfZGyhXHsrGKOcQKG9P48/XXXtb9mT7v8MEF N39bftlKZZ+0zjhond7l3s2rjJcVV428Jw7nBqnyQIIDMqWGvJjn5dT9uGskHZvbhodB3hOjd2T DYnUyEHCaQK6b4aNcn1eINf2ddxxFWNe9b+fzntQc4F3+hdX55pD8uiHQ8ruq+bhcWA== X-Received: by 2002:a9d:3b84:: with SMTP id k4mr47275825otc.27.1560698076269; Sun, 16 Jun 2019 08:14:36 -0700 (PDT) X-Google-Smtp-Source: APXvYqzShdp9sgLioq1hk9/UhFHk8beU/obA3KERTWzx3oMaRa+/CRyuIgP4vOHsIwlq2pdt/U9B X-Received: by 2002:a9d:3b84:: with SMTP id k4mr47275794otc.27.1560698075484; Sun, 16 Jun 2019 08:14:35 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1560698075; cv=none; d=google.com; s=arc-20160816; b=R0owjQJABNjmTv/qt6g/gHBgjUUQHURNgmPwgFIaJRGpXIotAGHZsHF0+L0oEkUtBC 10UzIZnsaxM29Pr3nQwFFSEJMRz12hyz1Mhg0M3/yzghrNKhK0AArOh0HcM7MTQZ6LQp 13sfi2phNsm/j5w+gJ2I+CAo9+KYOjQUMzp3MQxhQho68VGcqQo+70Er9cgI4hbVLYd2 M5N5VL2ZXN0bol8fuorM6AlpENZv7Ra714RRKD/wgEWvXJcy7Px4oJA+Qxgx94CgAKoB sv5rPqSZizhKjOkW8imyw0V6c/wySXc19z4beFLQYKgbj/PS0NaFgEIy3oTHIsQl9UWj ETfQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:references:cc:to:from:subject; bh=NYQJK/zo5XhCFiJZEOq4RoG1QrgP7TGctx8J6I5+Bw4=; b=VYnWgSWLb3WXceYjTBMcOd37MpbTmT9CrU34upSfONB8n8jyz4SJTTk7ti3BaDYaFu NzhGGvx3qoZtYrijjgYAN3FX++NtnH255sVH5kehNXZ8MLgsVFyh/cOZSRTC+5uSnflJ dF/3lwont7iw+TOttSchYTm/0Fuob+2CimnISmWFfTvkKKl3K2RTBOiOubwnt+D1N52t UjesV26aonCrUx0lDMvceI2KJ5XWHgyhMa63SRdrGfrYMmKHyUf0ic4LSxUgE5bQUmgM +whEWuQpOxqKa8Qw83N1Q2CzSNFnHM6U2t0tTA5HdECVjMqt48rQaJsLpojDdvVAl2e4 q3ag== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id c15si5331964otr.289.2019.06.16.08.14.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 16 Jun 2019 08:14:35 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) client-ip=202.181.97.72; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from fsav405.sakura.ne.jp (fsav405.sakura.ne.jp [133.242.250.104]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x5GFDnKk039427; Mon, 17 Jun 2019 00:13:49 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav405.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav405.sakura.ne.jp); Mon, 17 Jun 2019 00:13:49 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav405.sakura.ne.jp) Received: from [192.168.1.8] (softbank126012062002.bbtec.net [126.12.62.2]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x5GFDl0h039419 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Mon, 17 Jun 2019 00:13:48 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: general protection fault in oom_unkillable_task From: Tetsuo Handa To: Shakeel Butt Cc: Michal Hocko , syzbot , Andrew Morton , "Eric W. Biederman" , Roman Gushchin , Johannes Weiner , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , LKML , Linux MM , syzkaller-bugs , yuzhoujian@didichuxing.com References: <0000000000004143a5058b526503@google.com> <20190615134955.GA28441@dhcp22.suse.cz> <5bb1fe5d-f0e1-678b-4f64-82c8d5d81f61@i-love.sakura.ne.jp> <791594c6-45a3-d78a-70b5-901aa580ed9f@i-love.sakura.ne.jp> <840fa9f1-07e2-e206-2fc0-725392f96baf@i-love.sakura.ne.jp> Message-ID: Date: Mon, 17 Jun 2019 00:13:47 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <840fa9f1-07e2-e206-2fc0-725392f96baf@i-love.sakura.ne.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 2019/06/16 16:37, Tetsuo Handa wrote: > On 2019/06/16 6:33, Tetsuo Handa wrote: >> On 2019/06/16 3:50, Shakeel Butt wrote: >>>> While dump_tasks() traverses only each thread group, mem_cgroup_scan_tasks() >>>> traverses each thread. >>> >>> I think mem_cgroup_scan_tasks() traversing threads is not intentional >>> and css_task_iter_start in it should use CSS_TASK_ITER_PROCS as the >>> oom killer only cares about the processes or more specifically >>> mm_struct (though two different thread groups can have same mm_struct >>> but that is fine). >> >> We can't use CSS_TASK_ITER_PROCS from mem_cgroup_scan_tasks(). I've tried >> CSS_TASK_ITER_PROCS in an attempt to evaluate only one thread from each >> thread group, but I found that CSS_TASK_ITER_PROCS causes skipping whole >> threads in a thread group (and trivially allowing "Out of memory and no >> killable processes...\n" flood) if thread group leader has already exited. > > Seems that CSS_TASK_ITER_PROCS from mem_cgroup_scan_tasks() is now working. I found a reproducer and the commit. ---------------------------------------- #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include static const unsigned long size = 1048576 * 200; static int thread(void *unused) { int fd = open("/dev/zero", O_RDONLY); char *buf = mmap(NULL, size, PROT_WRITE | PROT_READ, MAP_ANONYMOUS | MAP_SHARED, EOF, 0); sleep(1); read(fd, buf, size); return syscall(__NR_exit, 0); } int main(int argc, char *argv[]) { FILE *fp; mkdir("/sys/fs/cgroup/memory/test1", 0755); fp = fopen("/sys/fs/cgroup/memory/test1/memory.limit_in_bytes", "w"); fprintf(fp, "%lu\n", size); fclose(fp); fp = fopen("/sys/fs/cgroup/memory/test1/tasks", "w"); fprintf(fp, "%u\n", getpid()); fclose(fp); clone(thread, malloc(8192) + 4096, CLONE_SIGHAND | CLONE_THREAD | CLONE_VM, NULL); return syscall(__NR_exit, 0); } ---------------------------------------- Here is a patch to use CSS_TASK_ITER_PROCS. >From 415e52cf55bc4ad931e4f005421b827f0b02693d Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Mon, 17 Jun 2019 00:09:38 +0900 Subject: [PATCH] mm: memcontrol: Use CSS_TASK_ITER_PROCS at mem_cgroup_scan_tasks(). Since commit c03cd7738a83b137 ("cgroup: Include dying leaders with live threads in PROCS iterations") corrected how CSS_TASK_ITER_PROCS works, mem_cgroup_scan_tasks() can use CSS_TASK_ITER_PROCS in order to check only one thread from each thread group. Signed-off-by: Tetsuo Handa --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index ba9138a..b09ff45 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1163,7 +1163,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg, struct css_task_iter it; struct task_struct *task; - css_task_iter_start(&iter->css, 0, &it); + css_task_iter_start(&iter->css, CSS_TASK_ITER_PROCS, &it); while (!ret && (task = css_task_iter_next(&it))) ret = fn(task, arg); css_task_iter_end(&it); -- 1.8.3.1