Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757359AbZFHQ3l (ORCPT ); Mon, 8 Jun 2009 12:29:41 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757269AbZFHQ3Z (ORCPT ); Mon, 8 Jun 2009 12:29:25 -0400 Received: from mail-qy0-f195.google.com ([209.85.221.195]:37973 "EHLO mail-qy0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757190AbZFHQ3Y convert rfc822-to-8bit (ORCPT ); Mon, 8 Jun 2009 12:29:24 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=ehlPuFz5/GkWzBVUa7jPcOl5k9P4sg+aCEE67VemZDuVHzoiyPqc5EODLP+y1+p2XH vcYaRTxo1Pt7pNHA3clhZRyGcPtyVDq/fQaG3Ta61fPpcwtKny4fIs/hdCozbIaus4Dh NW7dsQwEoeZ94YOI2Us6y7i8/WOm2e6YaEoco= MIME-Version: 1.0 In-Reply-To: <20090608091544.53a94235@nehalam> References: <20090608091544.53a94235@nehalam> Date: Mon, 8 Jun 2009 09:29:23 -0700 X-Google-Sender-Auth: 41bb024c702b9cdc Message-ID: Subject: Re: [Bug #13116] Can't boot with nosmp From: Dan Williams To: Stephen Hemminger Cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1774 Lines: 46 On Mon, Jun 8, 2009 at 9:15 AM, Stephen Hemminger wrote: > On Sun, ?7 Jun 2009 11:52:49 +0200 (CEST) > "Rafael J. Wysocki" wrote: > >> This message has been generated automatically as a part of a report >> of recent regressions. >> >> The following bug entry is on the current list of known regressions >> from 2.6.29. ?Please verify if it still should be listed and let me know >> (either way). >> >> >> Bug-Entry ? ? : http://bugzilla.kernel.org/show_bug.cgi?id=13116 >> Subject ? ? ? ? ? ? ? : Can't boot with nosmp >> Submitter ? ? : Stephen Hemminger >> Date ? ? ? ? ?: 2009-04-15 4:18 (54 days old) >> References ? ?: http://marc.info/?l=linux-kernel&m=123976917817920&w=4 >> Handled-By ? ?: Dan Williams >> >> > > I suspect this bit of code in dmaengine is the culprit: > > ? ? ? ?/* redistribute available channels */ > ? ? ? ?n = 0; > ? ? ? ?for_each_dma_cap_mask(cap, dma_cap_mask_all) > ? ? ? ? ? ? ? ?for_each_online_cpu(cpu) { > ? ? ? ? ? ? ? ? ? ? ? ?if (num_possible_cpus() > 1) > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?chan = nth_chan(cap, n++); > ? ? ? ? ? ? ? ? ? ? ? ?else > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?chan = nth_chan(cap, -1); > > Why does num_possible_cpus() == 1 have to be a special case? When there will only be one cpu the channel allocation policy changes from: "isolate a channel per cpu" ...to: "isolate a capability per channel". For example, isolating per channel allows a memcpy to run concurrently with an xor. -- 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/