From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luben Tuikov Subject: Re: [PATCH 2.6.12.5 1/2] lib: allow idr to be used in irq context Date: Sun, 21 Aug 2005 10:27:58 -0700 (PDT) Message-ID: <20050821172758.36512.qmail@web51608.mail.yahoo.com> References: <1124640387.5068.2.camel@mulgrave> Reply-To: luben_tuikov@adaptec.com Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Return-path: Received: from zeus1.kernel.org ([204.152.191.4]:42445 "EHLO zeus1.kernel.org") by vger.kernel.org with ESMTP id S1751163AbVHUVlu (ORCPT ); Sun, 21 Aug 2005 17:41:50 -0400 Received: from web51608.mail.yahoo.com (web51608.mail.yahoo.com [206.190.38.213]) by zeus1.kernel.org (8.13.1/8.13.1) with SMTP id j7LHTGjV012128 for ; Sun, 21 Aug 2005 10:29:18 -0700 In-Reply-To: <1124640387.5068.2.camel@mulgrave> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley , luben_tuikov@adaptec.com Cc: Andrew Morton , Jim Houston , Linux Kernel , SCSI Mailing List , Dave Jones , Jeff Garzik --- James Bottomley wrote: > On Sun, 2005-08-21 at 08:49 -0700, Luben Tuikov wrote: > > The caller is the aic94xx SAS LLDD. It uses IDR to generate unique > > task tag for each SCSI task being submitted. It is then used to lookup > > the task given the task tag, in effect using IDR as a fast lookup table. > > > > Yes, I'm also not aware of any other users of IDR from mixed process/IRQ > > context or for SCSI Task tag purposes. > > Just a minute, that's not what idr was designed for. It was really > designed for enumerations (like disk) presented to the user. That's why > using it in IRQ context hasn't been considered. Hi James, how are you? Is this the only use _you_ could find for a *radix tree*? ;-) Since of course sd.c uses it just as an enumeration, according to you this must be the only use? :-) It was designed as a general purpose id to pointer translation service, just as the comment in it says. > However, there is an infrastructure in the block layer called the > generic tag infrastructure which was designed precisely for this purpose > and which is designed to operate in IRQ context. James, I'm sure you're well aware that, - a request_queue is LU-bound, - a SCSI _transport_ (*ANY*) can _only_ address domain devices, but _not_ LUs. LUs are *not* seen on the domain. See the different associations? Then why are you posting such emails? Andrew, please apply this patch. Thanks, Luben