From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263879AbUEXDrz (ORCPT ); Sun, 23 May 2004 23:47:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263881AbUEXDrz (ORCPT ); Sun, 23 May 2004 23:47:55 -0400 Received: from fw.osdl.org ([65.172.181.6]:51609 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S263879AbUEXDry (ORCPT ); Sun, 23 May 2004 23:47:54 -0400 Date: Sun, 23 May 2004 20:47:51 -0700 (PDT) From: Linus Torvalds To: Benjamin Herrenschmidt cc: Andrew Morton , Linux Kernel list Subject: Re: [PATCH] ppc64: Fix possible race with set_pte on a present PTE In-Reply-To: <1085369393.15315.28.camel@gaston> Message-ID: References: <1085369393.15315.28.camel@gaston> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 24 May 2004, Benjamin Herrenschmidt wrote: > > There is a subtle race which can cause set_pte to be called on ppc64 on > a PTE that is already present (that normally doesn't happen for us) and > which itself, in the proper race condition, can trigger a duplicate hash > entry to be added to the hash table (very bad). So how exactly can the pte already be present? It's definitely illegal, since if that actually happened, that would imply a memory leak (whatever previous page was there just got silently dropped). Linus