From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: Re: [PATCH 8/9] iommu: add support for ARM Ltd. System MMU architecture Date: Fri, 21 Jun 2013 17:30:44 +0200 Message-ID: <20130621153044.GL11309@8bytes.org> References: <1370889285-22799-1-git-send-email-will.deacon@arm.com> <1370889285-22799-9-git-send-email-will.deacon@arm.com> <20130620212646.GG11309@8bytes.org> <20130621102318.GB7766@mudshark.cambridge.arm.com> <20130621141306.GJ11309@8bytes.org> <20130621150006.GG7766@mudshark.cambridge.arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20130621150006.GG7766-MRww78TxoiP5vMa5CHWGZ34zcgK1vI+I0E9HWUfgJXw@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Will Deacon Cc: Olav Haugan , "devicetree-discuss-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org" , "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" , Rob Herring , Andreas Herrmann , "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" List-Id: devicetree@vger.kernel.org On Fri, Jun 21, 2013 at 04:00:06PM +0100, Will Deacon wrote: > Damn, I was hoping to avoid locking on the map path. In fact, this is a good > argument to go with your suggestion below (otherwise I'd need to use > reader/writer locks which seem to be frowned on). You should look into using rcu-lists instead. You still need a lock, but only when you actually manipulating the lists. For traversing them it is sufficient to take the rcu_read_lock() which has very low overhead. Joerg From mboxrd@z Thu Jan 1 00:00:00 1970 From: joro@8bytes.org (Joerg Roedel) Date: Fri, 21 Jun 2013 17:30:44 +0200 Subject: [PATCH 8/9] iommu: add support for ARM Ltd. System MMU architecture In-Reply-To: <20130621150006.GG7766@mudshark.cambridge.arm.com> References: <1370889285-22799-1-git-send-email-will.deacon@arm.com> <1370889285-22799-9-git-send-email-will.deacon@arm.com> <20130620212646.GG11309@8bytes.org> <20130621102318.GB7766@mudshark.cambridge.arm.com> <20130621141306.GJ11309@8bytes.org> <20130621150006.GG7766@mudshark.cambridge.arm.com> Message-ID: <20130621153044.GL11309@8bytes.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Jun 21, 2013 at 04:00:06PM +0100, Will Deacon wrote: > Damn, I was hoping to avoid locking on the map path. In fact, this is a good > argument to go with your suggestion below (otherwise I'd need to use > reader/writer locks which seem to be frowned on). You should look into using rcu-lists instead. You still need a lock, but only when you actually manipulating the lists. For traversing them it is sufficient to take the rcu_read_lock() which has very low overhead. Joerg