From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH 2/2] scsi: don't use execute_in_process_context() Date: Wed, 15 Dec 2010 20:19:17 +0100 Message-ID: <4D0914B5.20208@kernel.org> References: <4CBD95C0.6060302@kernel.org> <4CBD95DC.8000001@kernel.org> <1292194113.2989.9.camel@mulgrave.site> <4D073E9A.3000608@kernel.org> <1292335754.3058.2.camel@mulgrave.site> <4D077CD9.6050907@kernel.org> <1292336798.3058.5.camel@mulgrave.site> <4D078052.3040800@kernel.org> <1292382245.19511.56.camel@mulgrave.site> <4D08E2FF.5090605@kernel.org> <1292428486.4688.180.camel@mulgrave.site> <4D08E624.3020808@kernel.org> <1292433773.4688.278.camel@mulgrave.site> <4D09116C.6010508@kernel.org> <1292440246.4688.416.camel@mulgrave.site> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: Received: from hera.kernel.org ([140.211.167.34]:59277 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754614Ab0LOTTY (ORCPT ); Wed, 15 Dec 2010 14:19:24 -0500 In-Reply-To: <1292440246.4688.416.camel@mulgrave.site> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Linux SCSI List , FUJITA Tomonori , lkml Hello, On 12/15/2010 08:10 PM, James Bottomley wrote: >> Yes, it would do, but we were already too far with the existing >> implementation and I don't agree we need more when replacing it with >> usual workqueue usage would remove the issue. So, when we actually >> need them, let's consider that or any other way to do it, please. >> A core API with only a few users which can be easily replaced isn't >> really worth keeping around. Wouldn't you agree? > > Not really ... since the fix is small and obvious. IMHO, it's a bit too subtle to be a good API. The callee is called under different (locking) context depending on the callsite and I've been already bitten enough times from implicit THIS_MODULEs. Both properties increase possbility of introducing problems which can be quite difficult to detect and reproduce. > Plus now it can't be moved into SCSI because I need the unremovable > call chain. Yes, with the proposed change, it cannot be moved to SCSI. > Show me how you propose to fix it differently first, since we both agree > the initial attempt doesn't work, and we can take the discussion from > there. Given that the structures containing the work items are dynamically allocated, I would introduce a scsi_wq, unconditionally schedule release works on them and flush them before unloading. Please note that workqueues no longer require dedicated threads, so it's quite cheap. Thanks. -- tejun