Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758030AbZDNSMb (ORCPT ); Tue, 14 Apr 2009 14:12:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756496AbZDNSMT (ORCPT ); Tue, 14 Apr 2009 14:12:19 -0400 Received: from mx2.redhat.com ([66.187.237.31]:39243 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755191AbZDNSMS (ORCPT ); Tue, 14 Apr 2009 14:12:18 -0400 From: Jeff Moyer To: Andrea Arcangeli 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) References: <20090414151204.C647.A69D9226@jp.fujitsu.com> <20090414151652.C64D.A69D9226@jp.fujitsu.com> <20090414152500.C65F.A69D9226@jp.fujitsu.com> <20090414175124.GC9809@random.random> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Tue, 14 Apr 2009 14:10:08 -0400 In-Reply-To: <20090414175124.GC9809@random.random> (Andrea Arcangeli's message of "Tue, 14 Apr 2009 19:51:24 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.60 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 792 Lines: 19 Andrea Arcangeli writes: > On Tue, Apr 14, 2009 at 12:45:41PM -0400, Jeff Moyer wrote: >> So, if you're continuously submitting async read I/O, you will starve >> out the fork() call indefinitely. I agree that you want to allow > > IIRC rwsem good enough to stop the down_read when a down_write is > blocked. Otherwise page fault flood in threads would also starve any > mmap or similar call. Still with this approach fork will start to hang Really? I don't actually see that in the code, have I missed it? Cheers, Jeff -- 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/