Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754346AbZCJKZ1 (ORCPT ); Tue, 10 Mar 2009 06:25:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754032AbZCJKZM (ORCPT ); Tue, 10 Mar 2009 06:25:12 -0400 Received: from yw-out-2324.google.com ([74.125.46.28]:61961 "EHLO yw-out-2324.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754013AbZCJKZL convert rfc822-to-8bit (ORCPT ); Tue, 10 Mar 2009 06:25:11 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=FlrCEKTRnYJCMZD0zb9SpFYlj9D5S1wTUi7gmRfTM1+bm+EPLTphc51o50QDFmbIY6 adG9xvBJbBCgvkXdFKiBOucYS9gyO6LkZahaTEKAKe4C/Sh/YrYNLSlmv3CF5G6RYzHg MhCzUAaimyqHc0QxF4DCSbs6IWMKTrMnqP/JY= MIME-Version: 1.0 In-Reply-To: <1236679631.5183.72.camel@dy> References: <1236321780-28718-1-git-send-email-cooloney@kernel.org> <1236321780-28718-3-git-send-email-cooloney@kernel.org> <20090306143756.738db0ee.akpm@linux-foundation.org> <1236679631.5183.72.camel@dy> Date: Tue, 10 Mar 2009 06:25:08 -0400 Message-ID: <8bd0f97a0903100325k6cbcf73ek8e5f3723b2c4bb0a@mail.gmail.com> Subject: Re: [PATCH 02/18] Blackfin Serial Driver: use barrier instead of cpu_relax for Blackfin SMP like patch From: Mike Frysinger To: gyang Cc: Andrew Morton , Bryan Wu , alan@lxorguk.ukuu.org.uk, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1276 Lines: 32 On Tue, Mar 10, 2009 at 06:07, gyang wrote: > On Fri, 2009-03-06 at 14:37 -0800, Andrew Morton wrote: >> On Fri,  6 Mar 2009 14:42:44 +0800 >> Bryan Wu wrote: >> >> > From: Graf Yang >> > >> > We are making a SMP like patch to blackfin, cpu_relax() is replaced by a >> > data cache flush function which will count it to a per-cpu counter. >> > If this serial function is called too early, the per-cpu data area have >> > not been initialized, this call will cause crash. >> >> That's a bug in blackfin architecture support.  The kernel should be >> able to call cpu_relax() at any time, surely.  It's a very low-level >> and simple thing. >> >> > So we'd like to use barrier() instead of cpu_relax(). >> > >> >> barrier() is purely a compiler concept.  We might as well just remove >> the cpu_relax() altogether. > > Do you mean remove cpu_relax(), and either not add barrier() here? afaik, early printk all runs before SMP is setup, so having it be a 100% busy wait is fine -mike -- 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/