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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 9F334C4167B for ; Thu, 10 Dec 2020 17:33:50 +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 5790523A7C for ; Thu, 10 Dec 2020 17:33:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5790523A7C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=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 ABBC76EAAC; Thu, 10 Dec 2020 17:33:49 +0000 (UTC) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by gabe.freedesktop.org (Postfix) with ESMTPS id 4F59E6E435 for ; Thu, 10 Dec 2020 17:33:48 +0000 (UTC) IronPort-SDR: qsTMPWfI26yHXgWan33RrNt8+oSTbOHC44whQchOJa0J8N5WqU187VvEWKRPMnClJHN86Yb23h y1zNVNWtfj4A== X-IronPort-AV: E=McAfee;i="6000,8403,9831"; a="174410664" X-IronPort-AV: E=Sophos;i="5.78,408,1599548400"; d="scan'208";a="174410664" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Dec 2020 09:33:46 -0800 IronPort-SDR: iC/JaJN3m9PcJcqH2fmlIliGAdC7gATM3yJ/SgI5sr3TLNMMXQ9h/KP3na9RwiSKf2INUeeh8y 7nZifG0f03Ow== X-IronPort-AV: E=Sophos;i="5.78,408,1599548400"; d="scan'208";a="320185818" Received: from unknown (HELO sdutt-i7) ([10.165.21.147]) by fmsmga008-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Dec 2020 09:33:46 -0800 Date: Thu, 10 Dec 2020 09:28:00 -0800 From: Matthew Brost To: Chris Wilson Message-ID: <20201210172758.GB21533@sdutt-i7> References: <20201207193824.18114-1-chris@chris-wilson.co.uk> <20201207193824.18114-6-chris@chris-wilson.co.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201207193824.18114-6-chris@chris-wilson.co.uk> User-Agent: Mutt/1.9.4 (2018-02-28) Subject: Re: [Intel-gfx] [PATCH 06/20] drm/i915/gt: Remove virtual breadcrumb before transfer 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: , Cc: intel-gfx@lists.freedesktop.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" On Mon, Dec 07, 2020 at 07:38:10PM +0000, Chris Wilson wrote: > The issue with stale virtual breadcrumbs remain. Now we have the problem > that if the irq-signaler is still referencing the stale breadcrumb as we > transfer it to a new sibling, the list becomes spaghetti. This is a very > small window, but that doesn't stop it being hit infrequently. To > prevent the lists being tangled (the iterator starting on one engine's > b->signalers but walking onto another list), always decouple the virtual > breadcrumb on schedule-out and make sure that the walker has stepped out > of the lists. > > Signed-off-by: Chris Wilson Makes sense to me. Reviewed-by: Matthew Brost > --- > drivers/gpu/drm/i915/gt/intel_breadcrumbs.c | 5 +++-- > drivers/gpu/drm/i915/gt/intel_lrc.c | 15 +++++++++++++++ > 2 files changed, 18 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c > index 00918300f53f..63900edbde88 100644 > --- a/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c > +++ b/drivers/gpu/drm/i915/gt/intel_breadcrumbs.c > @@ -454,15 +454,16 @@ void i915_request_cancel_breadcrumb(struct i915_request *rq) > { > struct intel_breadcrumbs *b = READ_ONCE(rq->engine)->breadcrumbs; > struct intel_context *ce = rq->context; > + unsigned long flags; > bool release; > > if (!test_and_clear_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) > return; > > - spin_lock(&ce->signal_lock); > + spin_lock_irqsave(&ce->signal_lock, flags); > list_del_rcu(&rq->signal_link); > release = remove_signaling_context(b, ce); > - spin_unlock(&ce->signal_lock); > + spin_unlock_irqrestore(&ce->signal_lock, flags); > if (release) > intel_context_put(ce); > > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c > index 0b7e86240f3b..b3db16b2a5a4 100644 > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c > @@ -1388,6 +1388,21 @@ static inline void execlists_schedule_in(struct i915_request *rq, int idx) > static void kick_siblings(struct i915_request *rq, struct intel_context *ce) > { > struct virtual_engine *ve = container_of(ce, typeof(*ve), context); > + struct intel_engine_cs *engine = rq->engine; > + > + /* Flush concurrent rcu iterators in signal_irq_work */ > + if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &rq->fence.flags)) { > + /* > + * After this point, the rq may be transferred to a new > + * sibling, so before we clear ce->inflight make sure that > + * the context has been removed from the b->signalers and > + * furthermore we need to make sure that the concurrent > + * iterator in signal_irq_work is no longer following > + * ce->signal_link. > + */ > + i915_request_cancel_breadcrumb(rq); > + irq_work_sync(&engine->breadcrumbs->irq_work); > + } > > if (READ_ONCE(ve->request)) > tasklet_hi_schedule(&ve->base.execlists.tasklet); > -- > 2.20.1 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx