Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755076AbZA3Mk4 (ORCPT ); Fri, 30 Jan 2009 07:40:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752127AbZA3Mks (ORCPT ); Fri, 30 Jan 2009 07:40:48 -0500 Received: from brick.kernel.dk ([93.163.65.50]:14003 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752194AbZA3Mks (ORCPT ); Fri, 30 Jan 2009 07:40:48 -0500 Date: Fri, 30 Jan 2009 13:38:58 +0100 From: Jens Axboe To: Peter Zijlstra Cc: Linus Torvalds , Steven Rostedt , Andrew Morton , LKML , Rusty Russell , npiggin@suse.de, Ingo Molnar , Thomas Gleixner , Arjan van de Ven Subject: Re: [PATCH -v3] use per cpu data for single cpu ipi calls Message-ID: <20090130123858.GQ30821@kernel.dk> References: <1233218954.7835.11.camel@twins> <1233253380.4495.123.camel@laptop> <1233254680.4495.126.camel@laptop> <20090130112310.GI30821@kernel.dk> <1233318733.4495.174.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1233318733.4495.174.camel@laptop> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1519 Lines: 42 On Fri, Jan 30 2009, Peter Zijlstra wrote: > On Fri, 2009-01-30 at 12:23 +0100, Jens Axboe wrote: > > > Peter, can you post a final complete patch for review and acks? > > Sure, Looks good, you can add my acked-by to that. One small comment: > if (!wait) { > + /* > + * We are calling a function on a single CPU > + * and we are not going to wait for it to finish. > + * We first try to allocate the data, but if we > + * fail, we fall back to use a per cpu data to pass > + * the information to that CPU. Since all callers > + * of this code will use the same data, we must > + * synchronize the callers to prevent a new caller > + * from corrupting the data before the callee > + * can access it. > + * > + * The CSD_FLAG_LOCK is used to let us know when > + * the IPI handler is done with the data. > + * The first caller will set it, and the callee > + * will clear it. The next caller must wait for > + * it to clear before we set it again. This > + * will make sure the callee is done with the > + * data before a new caller will use it. > + * We use spinlocks to manage the callers. > + */ That last sentence appears stale now, since there's no locking involved for the per-cpu csd. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/