Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753527Ab2FCLkT (ORCPT ); Sun, 3 Jun 2012 07:40:19 -0400 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:49831 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751210Ab2FCLkR (ORCPT ); Sun, 3 Jun 2012 07:40:17 -0400 Date: Sun, 3 Jun 2012 12:39:49 +0100 From: Russell King - ARM Linux To: "Srivatsa S. Bhat" Cc: Yong Zhang , "linux-kernel@vger.kernel.org" , Tony Luck , Ralf Baechle , Benjamin Herrenschmidt , Paul Mundt , Chris Metcalf , Konrad Rzeszutek Wilk , Mike Frysinger , Hirokazu Takata , Richard Kuo , David Howells , Bob Liu , "David S. Miller" , Richard Weinberger , Jesper Nilsson , "James E.J. Bottomley" , Martin Schwidefsky , Matt Turner , nikunj@linux.vnet.ibm.com Subject: Re: [PATCH 01/27] smpboot: Provide a generic method to boot secondary processors Message-ID: <20120603113948.GC15354@n2100.arm.linux.org.uk> References: <20120601090952.31979.24799.stgit@srivatsabhat.in.ibm.com> <20120601091008.31979.93586.stgit@srivatsabhat.in.ibm.com> <4FC8B0F7.3060705@linux.vnet.ibm.com> <20120603085359.GE16829@zhy> <4FCB4B9E.3090508@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4FCB4B9E.3090508@linux.vnet.ibm.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1453 Lines: 30 On Sun, Jun 03, 2012 at 05:03:50PM +0530, Srivatsa S. Bhat wrote: > That's a good point! But unfortunately we can't do that just yet. > Because, some architectures have explicit comments that say that > irqs must be enabled at a certain point in time, or have something > special than just a local_irq_enable(), and hence fall under the > __cpu_post_online() function when converted to this model. > > Examples: ARM (patch 26) and ia64 (patch 15) > > Unless the maintainers give a go-ahead to change them, I don't > think it would be safe.. (I have added the Notes section to each > patch to get the attention of the maintainers to such issues). I have no intention of touching ARMs SMP bringup any more than is absolutely necessary - this code is extremely fragile, and it's taken a long time to get it to where it presently is, where most people are happy with it. Especially problematical is stuff like where we enable interrupts in relation to other activities. It's probably best to describe the code not as "mostly bug free" but as "causes the least pain" because I don't think there is a solution which satisfies all the constraints placed upon this code path by the various parts of the kernel. -- 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/