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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 61239C38A2A for ; Fri, 8 May 2020 15:39:26 +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 405CB207DD for ; Fri, 8 May 2020 15:39:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 405CB207DD 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 B75CF6EB22; Fri, 8 May 2020 15:39:25 +0000 (UTC) Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by gabe.freedesktop.org (Postfix) with ESMTPS id 658336EB22 for ; Fri, 8 May 2020 15:39:25 +0000 (UTC) IronPort-SDR: Z3x1EeMo6j8Ne9D3h3UW8i3eVnEXjkeabOA96BY9nrPG9AvwIFmJbqgV8k99/7flyuY+EgnDi9 WECNvwQybDOQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 May 2020 08:39:24 -0700 IronPort-SDR: U8hTgzZlxJVOAwbyXOeOfJtuAbp5SeXhInWFnHfiAsyWeCRhB11Ss+xjS+VWvJNfREWFRH1Zcj 5HhSNsT3SCTA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,368,1583222400"; d="scan'208";a="250493177" Received: from gaia.fi.intel.com ([10.237.72.192]) by fmsmga007.fm.intel.com with ESMTP; 08 May 2020 08:39:23 -0700 Received: by gaia.fi.intel.com (Postfix, from userid 1000) id B0EF05C1DC1; Fri, 8 May 2020 18:37:15 +0300 (EEST) From: Mika Kuoppala To: Chris Wilson , intel-gfx@lists.freedesktop.org In-Reply-To: <20200508092933.738-3-chris@chris-wilson.co.uk> References: <20200508092933.738-1-chris@chris-wilson.co.uk> <20200508092933.738-3-chris@chris-wilson.co.uk> Date: Fri, 08 May 2020 18:37:15 +0300 Message-ID: <87a72ixwt0.fsf@gaia.fi.intel.com> MIME-Version: 1.0 Subject: Re: [Intel-gfx] [PATCH 3/9] drm/i915: Prevent using semaphores to chain up to external fences 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: Chris Wilson Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Chris Wilson writes: > The downside of using semaphores is that we lose metadata passing > along the signaling chain. This is particularly nasty when we > need to pass along a fatal error such as EFAULT or EDEADLK. For > fatal errors we want to scrub the request before it is executed, > which means that we cannot preload the request onto HW and have > it wait upon a semaphore. b is waiting on a, a fails and we want to release b with error? > > Signed-off-by: Chris Wilson > --- > drivers/gpu/drm/i915/i915_request.c | 26 +++++++++++++++++++++ > drivers/gpu/drm/i915/i915_scheduler_types.h | 1 + > 2 files changed, 27 insertions(+) > > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c > index 94189c7d43cd..f0f9393e2ade 100644 > --- a/drivers/gpu/drm/i915/i915_request.c > +++ b/drivers/gpu/drm/i915/i915_request.c > @@ -1002,6 +1002,15 @@ emit_semaphore_wait(struct i915_request *to, > if (!rcu_access_pointer(from->hwsp_cacheline)) > goto await_fence; > > + /* > + * If this or its dependents are waiting on an external fence > + * that may fail catastrophically, then we want to avoid using > + * sempahores as they bypass the fence signaling metadata, and we semaphore -Mika > + * lose the fence->error propagation. > + */ > + if (from->sched.flags & I915_SCHED_HAS_EXTERNAL_CHAIN) > + goto await_fence; > + > /* Just emit the first semaphore we see as request space is limited. */ > if (already_busywaiting(to) & mask) > goto await_fence; > @@ -1064,12 +1073,29 @@ i915_request_await_request(struct i915_request *to, struct i915_request *from) > return ret; > } > > + if (from->sched.flags & I915_SCHED_HAS_EXTERNAL_CHAIN) > + to->sched.flags |= I915_SCHED_HAS_EXTERNAL_CHAIN; > + > return 0; > } > > +static void mark_external(struct i915_request *rq) > +{ > + /* > + * The downside of using semaphores is that we lose metadata passing > + * along the signaling chain. This is particularly nasty when we > + * need to pass along a fatal error such as EFAULT or EDEADLK. For > + * fatal errors we want to scrub the request before it is executed, > + * which means that we cannot preload the request onto HW and have > + * it wait upon a semaphore. > + */ > + rq->sched.flags |= I915_SCHED_HAS_EXTERNAL_CHAIN; > +} > + > static int > i915_request_await_external(struct i915_request *rq, struct dma_fence *fence) > { > + mark_external(rq); > return i915_sw_fence_await_dma_fence(&rq->submit, fence, > fence->context ? I915_FENCE_TIMEOUT : 0, > I915_FENCE_GFP); > diff --git a/drivers/gpu/drm/i915/i915_scheduler_types.h b/drivers/gpu/drm/i915/i915_scheduler_types.h > index 7186875088a0..6ab2c5289bed 100644 > --- a/drivers/gpu/drm/i915/i915_scheduler_types.h > +++ b/drivers/gpu/drm/i915/i915_scheduler_types.h > @@ -66,6 +66,7 @@ struct i915_sched_node { > struct i915_sched_attr attr; > unsigned int flags; > #define I915_SCHED_HAS_SEMAPHORE_CHAIN BIT(0) > +#define I915_SCHED_HAS_EXTERNAL_CHAIN BIT(1) > intel_engine_mask_t semaphores; > }; > > -- > 2.20.1 _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx