From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754837AbZAISlD (ORCPT ); Fri, 9 Jan 2009 13:41:03 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753285AbZAISkt (ORCPT ); Fri, 9 Jan 2009 13:40:49 -0500 Received: from 8bytes.org ([88.198.83.132]:41035 "EHLO 8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753038AbZAISkt (ORCPT ); Fri, 9 Jan 2009 13:40:49 -0500 Date: Fri, 9 Jan 2009 19:40:48 +0100 From: Joerg Roedel To: Evgeniy Polyakov Cc: Joerg Roedel , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, mingo@redhat.com Subject: Re: [PATCH 03/16] dma-debug: add hash functions for dma_debug_entries Message-ID: <20090109184048.GE14298@8bytes.org> References: <1231517970-20288-1-git-send-email-joerg.roedel@amd.com> <1231517970-20288-4-git-send-email-joerg.roedel@amd.com> <20090109175542.GB30168@ioremap.net> <20090109181446.GB9466@8bytes.org> <20090109182339.GA31661@ioremap.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090109182339.GA31661@ioremap.net> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 09, 2009 at 09:23:39PM +0300, Evgeniy Polyakov wrote: > On Fri, Jan 09, 2009 at 07:14:46PM +0100, Joerg Roedel (joro@8bytes.org) wrote: > > > > +static struct hash_bucket *get_hash_bucket(struct dma_debug_entry *entry, > > > > + unsigned long *flags) > > > > +{ > > > > + int idx = hash_fn(entry); > > > > + unsigned long __flags; > > > > + > > > > + spin_lock_irqsave(&dma_entry_hash[idx].lock, __flags); > > > > + *flags = __flags; > > > > + return &dma_entry_hash[idx]; > > > > +} > > > > + > > > > +/* > > > > + * Give up exclusive access to the hash bucket > > > > + */ > > > > +static void put_hash_bucket(struct hash_bucket *bucket, > > > > + unsigned long *flags) > > > > +{ > > > > + unsigned long __flags = *flags; > > > > + > > > > + spin_unlock_irqrestore(&bucket->lock, __flags); > > > > +} > > > > > > Why do you need such ugly helpers? > > > > Because everything else I thought about here was even more ugly. But > > maybe you have a better idea? I tried to lock directly in the debug_ > > functions. But this is ugly and unnecessary code duplication. > > I believe that having direct locking in the debug_ functions is not a > duplication, anyone will have a direct vision on the locking and hash > array dereference, and this will be just one additional line compared to > the get_* call and the same number of lines for the put :) Even more additional lines because of the additional variables needed in every function. Anyway, I try it and if it does not look good I will keep that change ;) Joerg