From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) by kanga.kvack.org (Postfix) with ESMTP id 0C5866B0008 for ; Tue, 7 Aug 2018 06:19:22 -0400 (EDT) Received: by mail-pf1-f200.google.com with SMTP id p5-v6so10324191pfh.11 for ; Tue, 07 Aug 2018 03:19:22 -0700 (PDT) Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id a140-v6si1156278pfa.61.2018.08.07.03.19.20 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 07 Aug 2018 03:19:20 -0700 (PDT) Subject: Re: WARNING in try_charge From: Tetsuo Handa References: <0000000000006350880572c61e62@google.com> <20180806174410.GB10003@dhcp22.suse.cz> <20180806175627.GC10003@dhcp22.suse.cz> <078bde8d-b1b5-f5ad-ed23-0cd94b579f9e@i-love.sakura.ne.jp> <20180806203437.GK10003@dhcp22.suse.cz> <3cf8f630-73b7-20d4-8ad1-bb1c657ee30d@i-love.sakura.ne.jp> <20180806205519.GO10003@dhcp22.suse.cz> <9c03213f-c099-378b-e9fd-ed6f2a2afdc3@i-love.sakura.ne.jp> Message-ID: Date: Tue, 7 Aug 2018 19:19:08 +0900 MIME-Version: 1.0 In-Reply-To: <9c03213f-c099-378b-e9fd-ed6f2a2afdc3@i-love.sakura.ne.jp> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: syzbot , cgroups@vger.kernel.org, dvyukov@google.com, hannes@cmpxchg.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, vdavydov.dev@gmail.com On 2018/08/07 6:50, Tetsuo Handa wrote: > list_for_each_entry_safe(p, tmp, &oom_victim_list, oom_victim_list) { > struct mm_struct *mm = p->signal->oom_mm; > > if (oom_unkillable_task(p, oc->memcg, oc->nodemask)) > continue; > ret = true; > + /* > + * Since memcg OOM allows forced charge, we can safely wait > + * until __mmput() completes. > + */ > + if (is_memcg_oom(oc)) > + return true; Oops. If this OOM victim was blocked on some lock which current thread is holding, waiting forever unconditionally is not safe. > #ifdef CONFIG_MMU > /* > * Since the OOM reaper exists, we can safely wait until > * MMF_OOM_SKIP is set. > */ > if (!test_bit(MMF_OOM_SKIP, &mm->flags)) { > if (!oom_reap_target) { > get_task_struct(p); > oom_reap_target = p; > trace_wake_reaper(p->pid); > wake_up(&oom_reaper_wait); > } > #endif > continue; > } > #endif > /* We can wait as long as OOM score is decreasing over time. */ > if (!victim_mm_stalling(p, mm)) > continue; > gaveup = true; > list_del(&p->oom_victim_list); > /* Drop a reference taken by mark_oom_victim(). */ > put_task_struct(p); > } > if (gaveup) > debug_show_all_locks(); > > return ret; > } >