Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753284AbZDNTuN (ORCPT ); Tue, 14 Apr 2009 15:50:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752404AbZDNTuA (ORCPT ); Tue, 14 Apr 2009 15:50:00 -0400 Received: from mx2.redhat.com ([66.187.237.31]:55473 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751314AbZDNTt7 (ORCPT ); Tue, 14 Apr 2009 15:49:59 -0400 Date: Tue, 14 Apr 2009 21:48:25 +0200 From: Andrea Arcangeli To: Jeff Moyer Cc: KOSAKI Motohiro , LKML , Linus Torvalds , Andrew Morton , Nick Piggin , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, Hugh Dickins , Zach Brown , Andy Grover Subject: Re: [RFC][PATCH v3 2/6] mm, directio: fix fork vs direct-io race (read(2) side IOW gup(write) side) Message-ID: <20090414194825.GD9809@random.random> References: <20090414151204.C647.A69D9226@jp.fujitsu.com> <20090414151652.C64D.A69D9226@jp.fujitsu.com> <20090414152500.C65F.A69D9226@jp.fujitsu.com> <20090414175124.GC9809@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 659 Lines: 13 On Tue, Apr 14, 2009 at 02:10:08PM -0400, Jeff Moyer wrote: > Really? I don't actually see that in the code, have I missed it? Checking the spinlock version, when any writer is waiting, the sem->wait_list won't empty and down_read will wait too. The wakeup is FIFO with __rwsem_do_wake is doing a wake-one if first one in queue is a down_write. So it looks ok to me. asm version should have an equivalent logic. -- 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/