From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759070Ab0I0MMe (ORCPT ); Mon, 27 Sep 2010 08:12:34 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:45141 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755967Ab0I0MMd (ORCPT ); Mon, 27 Sep 2010 08:12:33 -0400 Date: Mon, 27 Sep 2010 13:12:28 +0100 From: Al Viro To: Ivan Kokshaysky Cc: Linus Torvalds , rth@twiddle.net, linux-kernel@vger.kernel.org Subject: Re: alpha: potential race around hae_cache in RESTORE_ALL Message-ID: <20100927121227.GB19804@ZenIV.linux.org.uk> References: <20100925181304.GV19804@ZenIV.linux.org.uk> <20100925191836.GW19804@ZenIV.linux.org.uk> <20100925192509.GX19804@ZenIV.linux.org.uk> <20100927075828.GA15344@jurassic.park.msu.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20100927075828.GA15344@jurassic.park.msu.ru> User-Agent: Mutt/1.5.20 (2009-08-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 27, 2010 at 11:58:28AM +0400, Ivan Kokshaysky wrote: > On Sat, Sep 25, 2010 at 08:25:09PM +0100, Al Viro wrote: > > BTW, am I right assuming that HAE modifications is UP-only thing? It would > > be obviously b0rken on any SMP box, since alpha_mv is not per-CPU thing... > > The only SMP system that does HAE modifications at runtime is T2, so it has > a spinlock protection around set_hae() - see core_t2.h. Others are either > limited to use HAE window 0 only, or do not have HAE hardware at all. Um? Pardon me, but that makes no sense; how would a spinlock taken in e.g. readl() stop another process from leaving a syscall, getting to RESTORE_ALL and overwriting HAE register while we are halfway through the spinlock-protected area?