Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755771Ab3CEJgV (ORCPT ); Tue, 5 Mar 2013 04:36:21 -0500 Received: from mail-qa0-f45.google.com ([209.85.216.45]:64417 "EHLO mail-qa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755642Ab3CEJgP (ORCPT ); Tue, 5 Mar 2013 04:36:15 -0500 Date: Tue, 5 Mar 2013 17:36:12 +0800 (HKT) From: Nicolas Pitre To: Joonsoo Kim cc: Russell King , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] ARM: mm: disable kmap_high_get() for SMP In-Reply-To: <1362372667-953-1-git-send-email-iamjoonsoo.kim@lge.com> Message-ID: References: <1362372667-953-1-git-send-email-iamjoonsoo.kim@lge.com> User-Agent: Alpine 2.03 (LFD 1266 2009-07-14) 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: 694 Lines: 19 On Mon, 4 Mar 2013, Joonsoo Kim wrote: > With SMP and enabling kmap_high_get(), it makes users of kmap_atomic() > sequential ordered, because kmap_high_get() use global kmap_lock(). > It is not welcome situation, so turn off this optimization for SMP. I'm not sure I understand the problem. The lock taken by kmap_high_get() is released right away before that function returns and therefore this is not actually serializing anything. Nicolas -- 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/