Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965849AbbD1Mh7 (ORCPT ); Tue, 28 Apr 2015 08:37:59 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:42500 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965617AbbD1Mh5 (ORCPT ); Tue, 28 Apr 2015 08:37:57 -0400 Date: Tue, 28 Apr 2015 14:37:38 +0200 From: Peter Zijlstra To: Davidlohr Bueso Cc: Thomas Gleixner , Sebastian Andrzej Siewior , Manfred Spraul , LKML , Ingo Molnar , Darren Hart , Steven Rostedt , fredrik.markstrom@windriver.com, "Paul E. McKenney" Subject: Re: [PATCH v2] ipc/mqueue: remove STATE_PENDING Message-ID: <20150428123738.GY23123@twins.programming.kicks-ass.net> References: <1428419030-20030-1-git-send-email-bigeasy@linutronix.de> <1428419030-20030-4-git-send-email-bigeasy@linutronix.de> <55241851.7060704@colorfullife.com> <20150410143726.GD3057@linutronix.de> <1430191493.2050.3.camel@stgolabs.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1430191493.2050.3.camel@stgolabs.net> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1096 Lines: 30 On Mon, Apr 27, 2015 at 08:24:53PM -0700, Davidlohr Bueso wrote: > +static inline void pipelined_send(struct wake_q_head *wake_q, > + struct mqueue_inode_info *info, > struct msg_msg *message, > struct ext_wait_queue *receiver) > { > receiver->msg = message; > list_del(&receiver->list); > + wake_q_add(wake_q, receiver->task); > + /* > + * Ensure that updating receiver->state is the last > + * write operation: As once set, the receiver can continue, > + * and if we don't have the reference count from the wake_q, > + * yet, at that point we can later have a use-after-free > + * condition and bogus wakeup. > + */ > + smp_wmb(); /* pairs with smp_rmb() in wq_sleep */ You have this barrier because we cannot rely on a failed cmpxchg() actually being a full barrier, right? > receiver->state = STATE_READY; > } -- 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/