From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id DF5675F0001 for ; Tue, 14 Apr 2009 14:10:04 -0400 (EDT) From: Jeff Moyer 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> 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: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org 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 List-ID: 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, 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