Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754997AbZIOQGy (ORCPT ); Tue, 15 Sep 2009 12:06:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754925AbZIOQGt (ORCPT ); Tue, 15 Sep 2009 12:06:49 -0400 Received: from mga01.intel.com ([192.55.52.88]:12600 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754757AbZIOQGs convert rfc822-to-8bit (ORCPT ); Tue, 15 Sep 2009 12:06:48 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.44,390,1249282800"; d="scan'208";a="727156790" From: "Sosnowski, Maciej" To: "Williams, Dan J" CC: "linux-kernel@vger.kernel.org" , "linux-raid@vger.kernel.org" Date: Tue, 15 Sep 2009 17:04:59 +0100 Subject: RE: [PATCH 01/18] dmaengine: add fence support Thread-Topic: [PATCH 01/18] dmaengine: add fence support Thread-Index: AcotKy9Asil1dvLSRamAnuEBCUTJ6AI8v+Wg Message-ID: <129600E5E5FB004392DDC3FB599660D7B5548783@irsmsx504.ger.corp.intel.com> References: <20090904064308.7141.30576.stgit@dwillia2-linux.ch.intel.com> <20090904064440.7141.72561.stgit@dwillia2-linux.ch.intel.com> In-Reply-To: <20090904064440.7141.72561.stgit@dwillia2-linux.ch.intel.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 966 Lines: 18 Williams, Dan J wrote: > Some engines optimize operation by reading ahead in the descriptor chain > such that descriptor2 may start execution before descriptor1 completes. > If descriptor2 depends on the result from descriptor1 then a fence is > required (on descriptor2) to disable this optimization. The async_tx > api could implicitly identify dependencies via the 'depend_tx' > parameter, but that would constrain cases where the dependency chain > only specifies a completion order rather than a data dependency. So, > provide an ASYNC_TX_FENCE to explicitly identify data dependencies. > > Signed-off-by: Dan Williams > --- Signed-off-by: Maciej Sosnowski -- 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/