Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758197Ab1FJWar (ORCPT ); Fri, 10 Jun 2011 18:30:47 -0400 Received: from smtp-out.google.com ([216.239.44.51]:11961 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754222Ab1FJWap (ORCPT ); Fri, 10 Jun 2011 18:30:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version:content-type; b=VQzDuH9clBeN55HW+H1FiMOUH9Xv3SlyU/9NY+HqBxERrHhYncL72vnlXF9qYGPaZt 0HIuK30jJ/LOx5vLV9JQ== Date: Fri, 10 Jun 2011 15:30:35 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Russell King - ARM Linux cc: Linus Torvalds , Dmitry Eremin-Solenikov , Andrew Morton , KOSAKI Motohiro , tglx@linutronix.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org, mel@csn.ul.ie, kamezawa.hiroyu@jp.fujitsu.com, riel@redhat.com, pavel@ucw.cz Subject: Re: [PATCH] Make GFP_DMA allocations w/o ZONE_DMA emit a warning instead of failing In-Reply-To: <20110610222020.GP24424@n2100.arm.linux.org.uk> Message-ID: References: <4DF1C9DE.4070605@jp.fujitsu.com> <20110610004331.13672278.akpm@linux-foundation.org> <20110610091233.GJ24424@n2100.arm.linux.org.uk> <20110610185858.GN24424@n2100.arm.linux.org.uk> <20110610220748.GO24424@n2100.arm.linux.org.uk> <20110610222020.GP24424@n2100.arm.linux.org.uk> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1460 Lines: 27 On Fri, 10 Jun 2011, Russell King - ARM Linux wrote: > So those platforms which don't have a DMA zone, don't have any problems > with DMA, yet want to use the very same driver which does have a problem > on ISA hardware have to also put up with a useless notification that > their kernel might be broken? > > Are you offering to participate on other architectures mailing lists to > answer all the resulting queries? > It all depends on the wording of the "warning", it should make it clear that this is not always an error condition and only affects certain types of hardware which the user may or may not have. If you have any suggestions on how to alter "task (pid): attempted to allocate DMA memory without DMA support -- enable CONFIG_ZONE_DMA if needed" to make that more clear, be my guest. The alternative is that the ISA hardware cannot handle the memory returned fails unexpectedly and randomly without any clear indication of what the issue is. I think what would be worse is time lost for someone to realize CONFIG_ZONE_DMA isn't enabled, and that could be significant (and probably generate many bug reports on its own) since it isn't immediately obvious without doing some debugging. -- 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/