From mboxrd@z Thu Jan 1 00:00:00 1970 From: "saeed bishara" Subject: Re: [md-accel PATCH 16/19] dmaengine: driver for the iop32x, iop33x, and iop13xx raid engines Date: Thu, 30 Aug 2007 21:43:05 +0300 Message-ID: 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <0C7297FA1D2D244A9C7F6959C0BF1E52025B10E4@azsmsx413.amr.corp.intel.com> Content-Disposition: inline Sender: linux-raid-owner@vger.kernel.org To: "Williams, Dan J" Cc: linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, neilb@suse.de, "Nelson, Shannon" List-Id: linux-raid.ids 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. saeed