Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761581AbXH3Ula (ORCPT ); Thu, 30 Aug 2007 16:41:30 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755238AbXH3UlV (ORCPT ); Thu, 30 Aug 2007 16:41:21 -0400 Received: from nf-out-0910.google.com ([64.233.182.189]:48257 "EHLO nf-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753684AbXH3UlU (ORCPT ); Thu, 30 Aug 2007 16:41:20 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=VCizB7ULTghBm4ZpCrmGI90AeB7mDeoefABHXMdQprrVrylqA54umjqsyME7dNZAMI5WY50C7qJDkferC46a8JkHImoN6CN5jtYZNxk8PBanRHcpgfSKCIKmNnacXIB4iP+w8lDYAT+GA+aPsCo92frj3DLv4XckWCVy1eC+pEU= Message-ID: Date: Thu, 30 Aug 2007 13:41:18 -0700 From: "Dan Williams" To: "saeed bishara" Subject: Re: [md-accel PATCH 16/19] dmaengine: driver for the iop32x, iop33x, and iop13xx raid engines Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, neilb@suse.de, "Nelson, Shannon" In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20070627014823.18962.96398.stgit@dwillia2-linux.ch.intel.com> <20070627015155.18962.88413.stgit@dwillia2-linux.ch.intel.com> <0C7297FA1D2D244A9C7F6959C0BF1E52025B10E4@azsmsx413.amr.corp.intel.com> X-Google-Sender-Auth: 412674f0d12e8bff Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2631 Lines: 67 On 8/30/07, saeed bishara wrote: > you are right, I've another question regarding the function > dma_wait_for_async_tx from async_tx.c, here is the body of the code: > /* poll through the dependency chain, return when tx is complete */ > 1. do { > 2. iter = tx; > 3. while (iter->cookie == -EBUSY) > 4. iter = iter->parent; > 5. > 6. status = dma_sync_wait(iter->chan, iter->cookie); > 7. } while (status == DMA_IN_PROGRESS || (iter != tx)); > > assume that: > - The interrupt capability is not provided. > - Request A was sent to chan 0 > - Request B that depends on A is sent to chan 1 > - Request C that depends on B is send to chan 2. > - Also, assume that when C is handled by async_tx_submit(), B is still > not queued to the dmaengine (cookie equals to -EBUSY). > > In this case, dma_wait_for_async_tx will be called for C, now, it > looks for me that the do while will loop forever, even when A gets > completed. this is because the iter will point to B after line 4, thus > the iter != tx (C) will always become true. > You are right. There are no drivers in the tree that can hit this, but it needs to be fixed up. I'll submit the following change: diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c index 0350071..bc18cbb 100644 --- a/crypto/async_tx/async_tx.c +++ b/crypto/async_tx/async_tx.c @@ -80,6 +80,7 @@ dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx) { enum dma_status status; struct dma_async_tx_descriptor *iter; + struct dma_async_tx_descriptor *parent; if (!tx) return DMA_SUCCESS; @@ -87,8 +88,15 @@ dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx) /* poll through the dependency chain, return when tx is complete */ do { iter = tx; - while (iter->cookie == -EBUSY) - iter = iter->parent; + + /* find the root of the unsubmitted dependency chain */ + while (iter->cookie == -EBUSY) { + parent = iter->parent; + if (parent && parent->cookie == -EBUSY) + iter = iter->parent; + else + break; + } > saeed Regards, Dan - 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/