From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750979AbWHASDb (ORCPT ); Tue, 1 Aug 2006 14:03:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751742AbWHASDb (ORCPT ); Tue, 1 Aug 2006 14:03:31 -0400 Received: from mga09.intel.com ([134.134.136.24]:9766 "EHLO orsmga102-1.jf.intel.com") by vger.kernel.org with ESMTP id S1750977AbWHASD3 convert rfc822-to-8bit (ORCPT ); Tue, 1 Aug 2006 14:03:29 -0400 X-IronPort-AV: i="4.07,203,1151910000"; d="scan'208"; a="100125073:sNHT16200786" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Subject: RE: [PATCH rev2 1/4] dmaengine: enable mutliple clients and operations Date: Tue, 1 Aug 2006 11:03:28 -0700 Message-ID: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: [PATCH rev2 1/4] dmaengine: enable mutliple clients and operations thread-index: Aca1MYiw2TM+oZoxT2qRGo1yllpmwwAXxAjQ From: "Leech, Christopher" To: "David Miller" , "Williams, Dan J" Cc: , , , X-OriginalArrivalTime: 01 Aug 2006 18:03:29.0129 (UTC) FILETIME=[CAF21D90:01C6B594] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Sorry Dave, The delay on that issue is my fault. While Dan is an Intel employee, he's in a totally separate part of the company (and a different state) from me and the other networking folks. I was trying to determine if reordering so that the spin_lock was inside the lock_cpu_hotplug would work, or if something else was needed, Dan suggested making the net_dma_event_lock a mutex, but then as Andrew pointed out as long as a lock is being held preemption is disabled and we're safe from cpu hotplug. Simple patch to remove the lock_cpu_hotplug/unlock_cpu_hotplug calls as Andrew suggested coming up. - Chris > -----Original Message----- > From: David Miller [mailto:davem@davemloft.net] > Sent: Monday, July 31, 2006 11:12 PM > To: Williams, Dan J > Cc: linux-kernel@vger.kernel.org; neilb@suse.de; > galak@kernel.crashing.org; Leech, Christopher; > alan@lxorguk.ukuu.org.uk > Subject: Re: [PATCH rev2 1/4] dmaengine: enable mutliple > clients and operations > > > > Can I ask that the known bugs in the I/O AT DMA code be fixed > before we start adding new features to it? > > Specifically, the lock_cpu_hotplug() call in net_dma_rebalance() > is still there and being invoked with a spinlock held. The > spinlock is grabbed by the caller, netdev_dma_event() which > grabs the net_dma_event_lock spinlock. > > You cannot invoke lock_cpu_hotplug() while holding a spinlock > because lock_cpu_hotplug(), as seen in kernel/cpu.c, takes > a semaphore which can sleep. Sleeping while holding a spinlock > is not allowed. > > This is the second time I have tried to make the Intel developers > aware of this bug. So please fix this problem. > > Thanks a lot. >