From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756883AbaAISfP (ORCPT ); Thu, 9 Jan 2014 13:35:15 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:37138 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754539AbaAISfI (ORCPT ); Thu, 9 Jan 2014 13:35:08 -0500 Date: Thu, 9 Jan 2014 10:35:07 -0800 From: Christoph Hellwig To: Jens Axboe Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] blk-mq: use __smp_call_function_single directly Message-ID: <20140109183507.GA23826@infradead.org> References: <20140108173337.GA29514@infradead.org> <52CDC3A3.5050203@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52CDC3A3.5050203@kernel.dk> User-Agent: Mutt/1.5.21 (2010-09-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 08, 2014 at 02:31:15PM -0700, Jens Axboe wrote: > On 01/08/2014 10:33 AM, Christoph Hellwig wrote: > > __smp_call_function_single already avoids multiple IPIs by internally > > queing up the items, and now also is available for non-SMP builds as > > a trivially correct stub, so there is no need to wrap it. If the > > additional lock roundtrip cause problems my patch to convert the > > generic IPI code to llists is waiting to get merged will fix it. > > Thanks Christoph, applied it. Btw, the same should be done to the null_blk ipi completion path in theory. But given that it always tries to IPI the local CPU __smp_call_function_single turns into a simple indirect function call, so I don't really understand the point of that code path at all.