From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f200.google.com (mail-qk0-f200.google.com [209.85.220.200]) by kanga.kvack.org (Postfix) with ESMTP id C00F26B025F for ; Wed, 15 Jun 2016 10:51:13 -0400 (EDT) Received: by mail-qk0-f200.google.com with SMTP id d2so59416433qkg.1 for ; Wed, 15 Jun 2016 07:51:13 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id d189si21530270qkb.84.2016.06.15.07.51.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 15 Jun 2016 07:51:13 -0700 (PDT) Date: Wed, 15 Jun 2016 16:51:06 +0200 From: Oleg Nesterov Subject: Re: [PATCH 05/10] mm, oom: skip vforked tasks from being selected Message-ID: <20160615145106.GC7944@redhat.com> References: <1465473137-22531-1-git-send-email-mhocko@kernel.org> <1465473137-22531-6-git-send-email-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1465473137-22531-6-git-send-email-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, Tetsuo Handa , David Rientjes , Vladimir Davydov , Andrew Morton , LKML , Michal Hocko On 06/09, Michal Hocko wrote: > > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -1883,6 +1883,32 @@ extern int arch_task_struct_size __read_mostly; > #define TNF_FAULT_LOCAL 0x08 > #define TNF_MIGRATE_FAIL 0x10 > > +static inline bool in_vfork(struct task_struct *tsk) > +{ > + bool ret; > + > + /* > + * need RCU to access ->real_parent if CLONE_VM was used along with > + * CLONE_PARENT. > + * > + * We check real_parent->mm == tsk->mm because CLONE_VFORK does not > + * imply CLONE_VM > + * > + * CLONE_VFORK can be used with CLONE_PARENT/CLONE_THREAD and thus > + * ->real_parent is not necessarily the task doing vfork(), so in > + * theory we can't rely on task_lock() if we want to dereference it. > + * > + * And in this case we can't trust the real_parent->mm == tsk->mm > + * check, it can be false negative. But we do not care, if init or > + * another oom-unkillable task does this it should blame itself. > + */ > + rcu_read_lock(); > + ret = tsk->vfork_done && tsk->real_parent->mm == tsk->mm; > + rcu_read_unlock(); > + > + return ret; > +} ACK, but why sched.h ? It has a single caller in oom_kill.c. Oleg. -- 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