Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755375Ab0DSQS4 (ORCPT ); Mon, 19 Apr 2010 12:18:56 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:56633 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754979Ab0DSQSy (ORCPT ); Mon, 19 Apr 2010 12:18:54 -0400 Subject: Re: Process-shared futexes on hugepages puts the kernel in an infinite loop in 2.6.32.11; is this fixed now? From: Peter Zijlstra To: Andrea Arcangeli Cc: Mel Gorman , r6144 , linux-kernel@vger.kernel.org, Darren Hart , tglx , Lee Schermerhorn In-Reply-To: <20100419161102.GZ32034@random.random> References: <1271432722.2564.16.camel@localhost.localdomain> <1271449668.1674.466.camel@laptop> <20100419114300.GT19264@csn.ul.ie> <1271677956.1674.922.camel@laptop> <20100419153245.GX19264@csn.ul.ie> <1271691905.1488.317.camel@laptop> <20100419161102.GZ32034@random.random> Content-Type: text/plain; charset="UTF-8" Date: Mon, 19 Apr 2010 18:18:48 +0200 Message-ID: <1271693928.1676.18.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1093 Lines: 26 On Mon, 2010-04-19 at 18:11 +0200, Andrea Arcangeli wrote: > On Mon, Apr 19, 2010 at 05:45:05PM +0200, Peter Zijlstra wrote: > > Wouldn't a longer poison be more recognisable? Also, shouldn't this use > > POISON_POINTER_DELTA? > > > > Something like: > > > > #define HUGETBL_POISON ((void *) 0x00300300 + POISON_POINTER_DELTA) > > > > 0x2e5 isn't that high, I've had actual derefs in that range. > > The default at kernel config time sets only 4k as unmapped (I think > it's a very bad default for 64bit archs), so above 4k userland can map > it and you can have actual derefs with 0x00300300 but not with Mel's > preferred <0x1000 address. So the address must be <0x1000. Well, most poison values have that problem and still we have them. Also on 64bit machines you can use POISON_POINTER_DELTA to map it outside the virtual address range. -- 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/