From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,HK_RANDOM_FROM,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE9FAC433F5 for ; Tue, 14 Sep 2021 12:28:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B4640610D1 for ; Tue, 14 Sep 2021 12:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233171AbhINM31 (ORCPT ); Tue, 14 Sep 2021 08:29:27 -0400 Received: from mga17.intel.com ([192.55.52.151]:60387 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232866AbhINM3U (ORCPT ); Tue, 14 Sep 2021 08:29:20 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10106"; a="202149936" X-IronPort-AV: E=Sophos;i="5.85,292,1624345200"; d="scan'208";a="202149936" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Sep 2021 05:28:02 -0700 X-IronPort-AV: E=Sophos;i="5.85,292,1624345200"; d="scan'208";a="432975337" Received: from ocascan-mobl.ger.corp.intel.com (HELO [10.213.234.116]) ([10.213.234.116]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Sep 2021 05:28:01 -0700 Subject: Re: [Intel-gfx] [PATCH 18/26] drm/i915: use new iterator in i915_gem_object_last_write_engine To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org Cc: daniel@ffwll.ch, intel-gfx@lists.freedesktop.org References: <20210913131707.45639-1-christian.koenig@amd.com> <20210913131707.45639-19-christian.koenig@amd.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <46a40614-b448-7f2d-7b6b-0705c4277e2b@linux.intel.com> Date: Tue, 14 Sep 2021 13:27:59 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210913131707.45639-19-christian.koenig@amd.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org On 13/09/2021 14:16, Christian König wrote: > This is maybe even a fix since the RCU usage here looks incorrect. What you think is incorrect? Pointless extra rcu locking? Also, FWIW, I submitted a patch to remove this function altogether since its IMO pretty useless, just failed in getting anyone to ack it so far. Regards, Tvrtko > Signed-off-by: Christian König > --- > drivers/gpu/drm/i915/gem/i915_gem_object.h | 15 +++++++-------- > 1 file changed, 7 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h > index e9eecebf5c9d..3343922af4d6 100644 > --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h > +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h > @@ -500,16 +500,15 @@ static inline struct intel_engine_cs * > i915_gem_object_last_write_engine(struct drm_i915_gem_object *obj) > { > struct intel_engine_cs *engine = NULL; > + struct dma_resv_cursor cursor; > struct dma_fence *fence; > > - rcu_read_lock(); > - fence = dma_resv_get_excl_unlocked(obj->base.resv); > - rcu_read_unlock(); > - > - if (fence && dma_fence_is_i915(fence) && !dma_fence_is_signaled(fence)) > - engine = to_request(fence)->engine; > - dma_fence_put(fence); > - > + dma_resv_for_each_fence_unlocked(obj->base.resv, &cursor, false, > + fence) { > + if (fence && dma_fence_is_i915(fence) && > + !dma_fence_is_signaled(fence)) > + engine = to_request(fence)->engine; > + } > return engine; > } > >