Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754565AbaG3POP (ORCPT ); Wed, 30 Jul 2014 11:14:15 -0400 Received: from e36.co.us.ibm.com ([32.97.110.154]:36477 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754488AbaG3POO (ORCPT ); Wed, 30 Jul 2014 11:14:14 -0400 Date: Wed, 30 Jul 2014 08:07:24 -0700 From: "Paul E. McKenney" To: Lai Jiangshan Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com Subject: Re: [PATCH RFC tip/core/rcu 1/9] rcu: Add call_rcu_tasks() Message-ID: <20140730150724.GK11241@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140728225556.GA19493@linux.vnet.ibm.com> <1406588180-21933-1-git-send-email-paulmck@linux.vnet.ibm.com> <53D89639.5080405@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53D89639.5080405@cn.fujitsu.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14073015-3532-0000-0000-0000037F2295 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 30, 2014 at 02:52:41PM +0800, Lai Jiangshan wrote: > On 07/29/2014 06:56 AM, Paul E. McKenney wrote: > > > + /* > > + * Each pass through the following loop scans the list > > + * of holdout tasks, removing any that are no longer > > + * holdouts. When the list is empty, we are done. > > + */ > > + while (!list_empty(&rcu_tasks_holdouts)) { > > + schedule_timeout_interruptible(HZ / 10); > > + flush_signals(current); > > + rcu_read_lock(); > > + list_for_each_entry_rcu(t, &rcu_tasks_holdouts, > > + rcu_tasks_holdout_list) { > > + if (smp_load_acquire(&t->rcu_tasks_holdout)) > > + continue; > > + list_del_init(&t->rcu_tasks_holdout_list); > > + /* @@@ need to check for usermode on CPU. */ > > + } > > + rcu_read_unlock(); > > Maybe I missed something. The task @t may already exited and we access to > the stale memory here if without patch 8/9. Yep, patch 8/9 is not optional. Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/