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=-1.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 C7E65C2D0CE for ; Tue, 21 Jan 2020 17:19:58 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A01F821569 for ; Tue, 21 Jan 2020 17:19:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A01F821569 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=intel-gfx-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 24BA26EDDF; Tue, 21 Jan 2020 17:19:58 +0000 (UTC) Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by gabe.freedesktop.org (Postfix) with ESMTPS id CCCE96EDDF for ; Tue, 21 Jan 2020 17:19:56 +0000 (UTC) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2020 09:19:56 -0800 X-IronPort-AV: E=Sophos;i="5.70,346,1574150400"; d="scan'208";a="228917187" Received: from wmszyfel-mobl2.ger.corp.intel.com (HELO [10.252.10.247]) ([10.252.10.247]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/AES256-SHA; 21 Jan 2020 09:19:55 -0800 To: Chris Wilson , intel-gfx@lists.freedesktop.org References: <20200121100927.114886-1-chris@chris-wilson.co.uk> <20200121130411.267092-1-chris@chris-wilson.co.uk> <524735a8-dc0c-fdfc-941a-5cc3afaac40e@linux.intel.com> <157961563444.4434.6318084724990340871@skylake-alporthouse-com> From: Tvrtko Ursulin Organization: Intel Corporation UK Plc Message-ID: <31d2ce9f-2a72-7471-1ad4-26ffa7091be6@linux.intel.com> Date: Tue, 21 Jan 2020 17:19:52 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <157961563444.4434.6318084724990340871@skylake-alporthouse-com> Content-Language: en-US Subject: Re: [Intel-gfx] [PATCH v3] drm/i915/execlists: Reclaim the hanging virtual request X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On 21/01/2020 14:07, Chris Wilson wrote: > Quoting Tvrtko Ursulin (2020-01-21 13:55:29) >> >> >> On 21/01/2020 13:04, Chris Wilson wrote: >>> + GEM_BUG_ON(!reset_in_progress(&engine->execlists)); >>> + >>> + /* >>> + * An unsubmitted request along a virtual engine will >>> + * remain on the active (this) engine until we are able >>> + * to process the context switch away (and so mark the >>> + * context as no longer in flight). That cannot have happened >>> + * yet, otherwise we would not be hanging! >>> + */ >>> + spin_lock_irqsave(&ve->base.active.lock, flags); >>> + GEM_BUG_ON(intel_context_inflight(rq->context) != engine); >>> + GEM_BUG_ON(ve->request != rq); >>> + ve->request = NULL; >>> + spin_unlock_irqrestore(&ve->base.active.lock, flags); >>> + >>> + rq->engine = engine; >> >> Lets see I understand this... tasklet has been disabled and ring paused. >> But we find an uncompleted request in the ELSP context, with rq->engine >> == virtual engine. Therefore this cannot be the first request on this >> timeline but has to be later. > > Not quite. > > engine->execlists.active[] tracks the HW, it get's updated only upon > receiving HW acks (or we reset). > > So if execlists_active()->engine == virtual, it can only mean that the > inflight _hanging_ request has already been unsubmitted by an earlier > preemption in execlists_dequeue(), but that preemption has not yet been > processed by the HW. (Hence the preemption-reset underway.) > > Now while we coalesce the requests for a context into a single ELSP[] > slot, and only record the last request submitted for a context, we have > to walk back along that context's timeline to find the earliest > incomplete request and blame the hang upon it. > > For a virtual engine, it's much simpler as there is only ever one > request in flight, but I don't think that has any impact here other > than that we only need to repair the single unsubmitted request that was > returned to the virtual engine. > >> One which has been put on the runqueue but >> not yet submitted to hw. (Because one at a time.) Or it has been >> unsubmitted by __unwind_incomplete_request already. In the former case >> why move it to the physical engine? Also in the latter actually, it >> would overwrite rq->engine with the physical one. > > Yes. For incomplete preemption event, the request is *still* on this > engine and has not been released (rq->context->inflight == engine, so it > cannot be submitted to any other engine, until after we acknowledge the > context has been saved and is no longer being accessed by HW.) It is > legal for us to process the hanging request along this engine; we have a > suboptimal decision to return the request to the same engine after the > reset, but since we have replaced the hanging payload, the request is a > mere signaling placeholder (and I do not think will overly burden the > system and negatively impact other virtual engines). What if the request in elsp actually completed in the meantime eg. preemption timeout was a false positive? In execlists_capture we do: cap->rq = execlists_active(&engine->execlists); This gets a completed request, then we do: cap->rq = active_request(cap->rq->context->timeline, cap->rq); This walks along the virtual timeline and finds a next virtual request. It then binds this request to a physical engine and sets ve->request to NULL. Then on unhold ve->submit_notify is called which sets ve->request to this request but the rq->engine points to the physical engine. Regards, Tvrtko _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx