From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422781Ab2JXWZZ (ORCPT ); Wed, 24 Oct 2012 18:25:25 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:43900 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161227Ab2JXWZY (ORCPT ); Wed, 24 Oct 2012 18:25:24 -0400 Message-ID: <1351117520.2494.8.camel@dabdike> Subject: Re: Drivers: scsi From: James Bottomley To: "K. Y. Srinivasan" Cc: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, devel@linuxdriverproject.org, ohering@suse.com, hch@infradead.org, linux-scsi@vger.kernel.org Date: Thu, 25 Oct 2012 07:25:20 +0900 In-Reply-To: <1351095938-12204-1-git-send-email-kys@microsoft.com> References: <1351095938-12204-1-git-send-email-kys@microsoft.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.4.4 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2012-10-24 at 09:25 -0700, K. Y. Srinivasan wrote: > When the low level driver returns SCSI_MLQUEUE_DEVICE_BUSY, > how is the command retried; I suspect the retry is done after some delay. Delay depends mainly on I/O pressure and the unplug timer in the block layer. > Is this delay programmable? If the device state changes, > can the low level driver notify upper layers that it can now handle > the command that it had failed earlier with SCSI_MLQUEUE_DEVICE_BUSY. In theory, you can call blk_run_queue() from the event handler that sees the device become ready. I don't think any driver actually does this, but I can't see it would cause any problem. James