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=-14.3 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=ham 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 ABAF3C433F5 for ; Mon, 20 Sep 2021 10:33:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 894C760F36 for ; Mon, 20 Sep 2021 10:33:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231318AbhITKet (ORCPT ); Mon, 20 Sep 2021 06:34:49 -0400 Received: from mga01.intel.com ([192.55.52.88]:57475 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230510AbhITKet (ORCPT ); Mon, 20 Sep 2021 06:34:49 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10112"; a="245508309" X-IronPort-AV: E=Sophos;i="5.85,308,1624345200"; d="scan'208";a="245508309" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Sep 2021 03:33:22 -0700 X-IronPort-AV: E=Sophos;i="5.85,308,1624345200"; d="scan'208";a="473549879" Received: from gbradyx-mobl2.ger.corp.intel.com (HELO [10.213.235.119]) ([10.213.235.119]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Sep 2021 03:33:20 -0700 Subject: Re: [Intel-gfx] [PATCH 13/26] drm/i915: use the new iterator in i915_gem_busy_ioctl To: =?UTF-8?Q?Christian_K=c3=b6nig?= , linaro-mm-sig@lists.linaro.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, intel-gfx@lists.freedesktop.org Cc: daniel@ffwll.ch References: <20210917123513.1106-1-christian.koenig@amd.com> <20210917123513.1106-14-christian.koenig@amd.com> <6fbaca09-ec51-c44e-708c-334ef8be8595@linux.intel.com> <368e8495-f4de-cbb2-3584-e022a5937885@gmail.com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <563bb7c3-f956-212d-6085-b1b88292887c@linux.intel.com> Date: Mon, 20 Sep 2021 11:33:17 +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: <368e8495-f4de-cbb2-3584-e022a5937885@gmail.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 20/09/2021 11:13, Christian König wrote: > Am 20.09.21 um 10:45 schrieb Tvrtko Ursulin: >> >> On 17/09/2021 13:35, Christian König wrote: >>> This makes the function much simpler since the complex >>> retry logic is now handled else where. >>> >>> Signed-off-by: Christian König >>> --- >>>   drivers/gpu/drm/i915/gem/i915_gem_busy.c | 32 ++++++++---------------- >>>   1 file changed, 11 insertions(+), 21 deletions(-) >>> >>> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> index 6234e17259c1..b1cb7ba688da 100644 >>> --- a/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> +++ b/drivers/gpu/drm/i915/gem/i915_gem_busy.c >>> @@ -82,8 +82,8 @@ i915_gem_busy_ioctl(struct drm_device *dev, void >>> *data, >>>   { >>>       struct drm_i915_gem_busy *args = data; >>>       struct drm_i915_gem_object *obj; >>> -    struct dma_resv_list *list; >>> -    unsigned int seq; >>> +    struct dma_resv_iter cursor; >>> +    struct dma_fence *fence; >>>       int err; >>>         err = -ENOENT; >>> @@ -109,27 +109,17 @@ i915_gem_busy_ioctl(struct drm_device *dev, >>> void *data, >>>        * to report the overall busyness. This is what the wait-ioctl >>> does. >>>        * >>>        */ >>> -retry: >>> -    seq = raw_read_seqcount(&obj->base.resv->seq); >>> - >>> -    /* Translate the exclusive fence to the READ *and* WRITE engine */ >>> -    args->busy = >>> busy_check_writer(dma_resv_excl_fence(obj->base.resv)); >>> - >>> -    /* Translate shared fences to READ set of engines */ >>> -    list = dma_resv_shared_list(obj->base.resv); >>> -    if (list) { >>> -        unsigned int shared_count = list->shared_count, i; >>> - >>> -        for (i = 0; i < shared_count; ++i) { >>> -            struct dma_fence *fence = >>> -                rcu_dereference(list->shared[i]); >>> - >>> +    args->busy = false; >>> +    dma_resv_iter_begin(&cursor, obj->base.resv, true); >>> +    dma_resv_for_each_fence_unlocked(&cursor, fence) { >> >> You did not agree with my suggestion to reset args->busy on restart >> and so preserve current behaviour? > > No, I want to keep the restart behavior internally to the dma_resv > object and as far as I can see it should not make a difference here. To be clear, on paper difference between old and new implementation is if the restart happens while processing the shared fences. Old implementation unconditionally goes to "args->busy = >>> busy_check_writer(dma_resv_excl_fence(obj->base.resv));" and so overwrites the set of flags returned to userspace. New implementation can merge new read flags to the old set of flags and so return a composition of past and current fences. Maybe it does not matter hugely in this case, depends if userspace typically just restarts until flags are clear. But I am not sure. On the higher level - what do you mean with wanting to keep the restart behaviour internal? Not providing iterators users means of detecting it? I think it has to be provided. Regards, Tvrtko > Regards, > Christian. > >> >> Regards, >> >> Tvrtko >> >>> +        if (dma_resv_iter_is_exclusive(&cursor)) >>> +            /* Translate the exclusive fence to the READ *and* WRITE >>> engine */ >>> +            args->busy = busy_check_writer(fence); >>> +        else >>> +            /* Translate shared fences to READ set of engines */ >>>               args->busy |= busy_check_reader(fence); >>> -        } >>>       } >>> - >>> -    if (args->busy && read_seqcount_retry(&obj->base.resv->seq, seq)) >>> -        goto retry; >>> +    dma_resv_iter_end(&cursor); >>>         err = 0; >>>   out: >>> >