From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Bart Van Assche" Subject: Re: [PATCH 2.6.25.1] Add scsi_execute_async_fifo() Date: Thu, 8 May 2008 17:02:50 +0200 Message-ID: References: <200805021638.42972.bart.vanassche@gmail.com> <20080502153306.GB7376@infradead.org> <20080502155525.GA16353@infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from fg-out-1718.google.com ([72.14.220.159]:47359 "EHLO fg-out-1718.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764668AbYEHPCw (ORCPT ); Thu, 8 May 2008 11:02:52 -0400 Received: by fg-out-1718.google.com with SMTP id 19so542377fgg.17 for ; Thu, 08 May 2008 08:02:50 -0700 (PDT) In-Reply-To: Content-Disposition: inline Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Christoph Hellwig Cc: James Bottomley , linux-scsi@vger.kernel.org, Vladislav Bolkhovitin , scst-devel@lists.sourceforge.net On Sun, May 4, 2008 at 5:30 PM, Bart Van Assche wrote: > On Fri, May 2, 2008 at 5:55 PM, Christoph Hellwig wrote: >> On Fri, May 02, 2008 at 05:53:22PM +0200, Bart Van Assche wrote: >>> Regarding scsi_execute_async(): I didn't know that this API is on its >>> way out. What will it be replaced by, and when ? >> >> blk_execute_rq/blk_execute_rq_nowait plus the block level helpers built >> ontop to build requests. > > Source reading learned me that the function scsi_execute_async() calls > blk_execute_rq_nowait() with 1 as fourth argument, which means that > the request is inserted at the head of the queue. This means that > requests queued with scsi_execute_async() are executed before other > queued requests, and that this function has LIFO (last in first out) > semantics. > > All non-SCSI calls to blk_execute_rq() / blk_execute_rq_nowait() add > requests at the end of the queue (except those calls for terminating > I/O). > > What is the background of this special behavior of the SCSI subsystem ? Is the linux-scsi mailing list the appropriate mailing list to post questions like the above ? Bart.