From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Gleixner Subject: Re: [PATCH RFC: linux-next 1/2] irq: Add CPU mask affinity hint callback framework Date: Thu, 29 Apr 2010 21:48:24 +0200 (CEST) Message-ID: References: <20100419045741.30276.23233.stgit@ppwaskie-hc2.jf.intel.com> <1272563946.9614.1.camel@localhost> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "davem@davemloft.net" , "arjan@linux.jf.intel.com" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" To: Peter P Waskiewicz Jr Return-path: In-Reply-To: <1272563946.9614.1.camel@localhost> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org B1;2005;0cPeter, On Thu, 29 Apr 2010, Peter P Waskiewicz Jr wrote: > On Wed, 2010-04-28 at 09:45 -0700, Thomas Gleixner wrote: > > So you need a reference to your device, so what about the following: > > > > struct irq_affinity_hint; > > > > struct irq_affinity_hint { > > unsigned int (*callback)(unsigned int irq, struct irq_affinity_hint *hint, > > cpumask_var_t *mask); > > } > > > > Now you embed that struct into your device private data structure and > > you get the reference to it back in the callback function. No extra > > kmalloc/kfree, less code. > > Good idea! I'll roll that into my new version. Thinking more about it, I wonder whether you have a cpu_mask in your driver/device private data anyway. I bet you have :) So it should be sufficient to set a pointer to that cpu_mask in irq_desc and get rid of the callback completely. Any access to desc->affinity_hint needs to be protected by desc->lock. For setting the pointer to a real mask resp. NULL that's fine. The copy which you need to do in the proc-read function is not going to introduce huge latencies either. Thanks, tglx