From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751828AbeBTMbU (ORCPT ); Tue, 20 Feb 2018 07:31:20 -0500 Received: from mail-wr0-f182.google.com ([209.85.128.182]:36352 "EHLO mail-wr0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751630AbeBTMbR (ORCPT ); Tue, 20 Feb 2018 07:31:17 -0500 X-Google-Smtp-Source: AH8x225P59gR02Aavfdtc6MqM/mMk0dwDcaSGUpapGApPXIm4GPaaB2cqpc86x2e2rljEH91Ih90dA== Reply-To: christian.koenig@amd.com Subject: Re: [PATCH 1/3] locking/ww_mutex: cleanup lock->ctx usage in amdgpu To: christian.koenig@amd.com, dri-devel@lists.freedesktop.org, amd-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org References: <20180215141944.4332-1-christian.koenig@amd.com> <20180219152421.GQ22199@phenom.ffwll.local> <20180219161544.GY22199@phenom.ffwll.local> <2e696981-6b4a-e292-c16a-0f3477dbf8ce@gmail.com> <20180219164354.GB22199@phenom.ffwll.local> <20180220113318.GN22199@phenom.ffwll.local> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <9c0175bd-cd5e-e643-de9b-5b2f6b2449a1@gmail.com> Date: Tue, 20 Feb 2018 13:31:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <20180220113318.GN22199@phenom.ffwll.local> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 20.02.2018 um 12:33 schrieb Daniel Vetter: > [SNIP] > Ah, so the ttm_ctx I've spotted was something entirely different and > doesn't contain the ww_acquire_ctx (I didn't check)? I'd assume you have > the same ctx passed around to everything in ttm, but if that doesn't exist > then we can indeed not annotate ww_mutex_trylock_ctx with the right ctx. Yes, exactly. I actually tried this approach, e.g. put the ww_acquire_context into the ttm_operation_context and then use that with ww_mutex_trylock_ctx. But a) that turned out to be to much hassle, e.g. at least amdgpu doesn't use a ww_acquire context in most cases. And b) it actually wasn't what I was looking for, e.g. I couldn't distinct between the trylocked BOs an everything else any more. >> [SNIP] >> But to me it actually looks more like that makes it unnecessary complicated. >> The use case in amdgpu which could only check the context isn't performance >> critical. > Oh I'm not worried about the runtime overhead at all, I'm worried about > conceptual clarity of this stuff. If you have a ctx there's no need to > also look at ->owner. > > Another idea: We drop the task argument from functions and go with the > following logic: > > ww_mutex_is_owner(lock, ctx) > { > if (ctx) > return lock->ctx == ctx; > else > return lock->owner == current; > } > > I think that would solve your use case, and gives us the neat interface > I'm aiming for. Kerneldoc can then explain what's happening for a NULL > ctx. Good point, going to adjust the patches this way and resend. Christian.