From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id B7BEC6B0003 for ; Wed, 7 Mar 2018 15:56:25 -0500 (EST) Received: by mail-io0-f198.google.com with SMTP id q197so3472202iod.17 for ; Wed, 07 Mar 2018 12:56:25 -0800 (PST) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id q4sor9399788ioe.228.2018.03.07.12.56.24 for (Google Transport Security); Wed, 07 Mar 2018 12:56:24 -0800 (PST) Date: Wed, 7 Mar 2018 12:56:21 -0800 (PST) From: David Rientjes Subject: Re: [PATCH] mm: oom: Fix race condition between oom_badness and do_exit of task In-Reply-To: <1520427454-22813-1-git-send-email-gkohli@codeaurora.org> Message-ID: References: <1520427454-22813-1-git-send-email-gkohli@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Gaurav Kohli Cc: akpm@linux-foundation.org, mhocko@suse.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org On Wed, 7 Mar 2018, Gaurav Kohli wrote: > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 6fd9773..5f4cc4b 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -114,9 +114,11 @@ struct task_struct *find_lock_task_mm(struct task_struct *p) > > for_each_thread(p, t) { > task_lock(t); > + get_task_struct(t); > if (likely(t->mm)) > goto found; > task_unlock(t); > + put_task_struct(t); > } > t = NULL; > found: We hold rcu_read_lock() here, so perhaps only do get_task_struct() before doing rcu_read_unlock() and we have a non-NULL t? > @@ -191,6 +193,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > test_bit(MMF_OOM_SKIP, &p->mm->flags) || > in_vfork(p)) { > task_unlock(p); > + put_task_struct(p); > return 0; > } > > @@ -208,7 +211,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg, > */ > if (has_capability_noaudit(p, CAP_SYS_ADMIN)) > points -= (points * 3) / 100; > - > + put_task_struct(p); > /* Normalize to oom_score_adj units */ > adj *= totalpages / 1000; > points += adj; This fixes up oom_badness(), but there are other users of find_lock_task_mm() in the oom killer as well as other subsystems. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org