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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 EB06DC433E1 for ; Mon, 13 Jul 2020 13:28:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE4DC206F0 for ; Mon, 13 Jul 2020 13:28:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729700AbgGMN2N convert rfc822-to-8bit (ORCPT ); Mon, 13 Jul 2020 09:28:13 -0400 Received: from mail.fireflyinternet.com ([77.68.26.236]:59942 "EHLO fireflyinternet.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1729649AbgGMN2N (ORCPT ); Mon, 13 Jul 2020 09:28:13 -0400 X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 21804017-1500050 for multiple; Mon, 13 Jul 2020 14:28:04 +0100 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT In-Reply-To: <20200713131738.21319-1-chris@chris-wilson.co.uk> References: <20200713131617.21175-1-chris@chris-wilson.co.uk> <20200713131738.21319-1-chris@chris-wilson.co.uk> Subject: Re: [PATCH] drm/i915: Skip signaling a signaled request From: Chris Wilson Cc: Tvrtko Ursulin , "Nayana, Venkata Ramana" , stable@vger.kernel.org To: intel-gfx@lists.freedesktop.org Date: Mon, 13 Jul 2020 14:28:04 +0100 Message-ID: <159464688483.23097.2677088254913725179@build.alporthouse.com> User-Agent: alot/0.9 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org Quoting Chris Wilson (2020-07-13 14:17:38) > Preempt-to-busy introduces various fascinating complications in that the > requests may complete as we are unsubmitting them from HW. As they may > then signal after unsubmission, we may find ourselves having to cleanup > the signaling request from within the signaling callback. This causes us > to recurse onto the same i915_request.lock. > > However, if the request is already signaled (as it will be before we > enter the signal callbacks), we know we can skip the signaling of that > request during submission, neatly evading the spinlock recursion. > > unsubmit(ve.rq0) # timeslice expiration or other preemption > -> virtual_submit_request(ve.rq0) > dma_fence_signal(ve.rq0) # request completed before preemption ack > -> submit_notify(ve.rq1) > -> virtual_submit_request(ve.rq1) # sees that we have completed ve.rq0 > -> __i915_request_submit(ve.rq0) > > [ 264.210142] BUG: spinlock recursion on CPU#2, sample_multi_tr/2093 > [ 264.210150] lock: 0xffff9efd6ac55080, .magic: dead4ead, .owner: sample_multi_tr/2093, .owner_cpu: 2 > [ 264.210155] CPU: 2 PID: 2093 Comm: sample_multi_tr Tainted: G U > [ 264.210158] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWR1.R00.X212.B01.1909060036 09/06/2019 > [ 264.210160] Call Trace: > [ 264.210167] dump_stack+0x98/0xda > [ 264.210174] spin_dump.cold+0x24/0x3c > [ 264.210178] do_raw_spin_lock+0x9a/0xd0 > [ 264.210184] _raw_spin_lock_nested+0x6a/0x70 > [ 264.210314] __i915_request_submit+0x10a/0x3c0 [i915] > [ 264.210415] virtual_submit_request+0x9b/0x380 [i915] > [ 264.210516] submit_notify+0xaf/0x14c [i915] > [ 264.210602] __i915_sw_fence_complete+0x8a/0x230 [i915] > [ 264.210692] i915_sw_fence_complete+0x2d/0x40 [i915] > [ 264.210762] __dma_i915_sw_fence_wake+0x19/0x30 [i915] > [ 264.210767] dma_fence_signal_locked+0xb1/0x1c0 > [ 264.210772] dma_fence_signal+0x29/0x50 > [ 264.210871] i915_request_wait+0x5cb/0x830 [i915] > [ 264.210876] ? dma_resv_get_fences_rcu+0x294/0x5d0 > [ 264.210974] i915_gem_object_wait_fence+0x2f/0x40 [i915] > [ 264.211084] i915_gem_object_wait+0xce/0x400 [i915] > [ 264.211178] i915_gem_wait_ioctl+0xff/0x290 [i915] > > Signed-off-by: Chris Wilson > Fixes: 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy") > References: 6d06779e8672 ("drm/i915: Load balancing across a virtual engine") > Signed-off-by: Chris Wilson > Cc: Tvrtko Ursulin > Cc: "Nayana, Venkata Ramana" > Cc: # v5.4+ > --- > drivers/gpu/drm/i915/i915_request.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c > index 3bb7320249ae..9b74a1bea5db 100644 > --- a/drivers/gpu/drm/i915/i915_request.c > +++ b/drivers/gpu/drm/i915/i915_request.c > @@ -560,9 +560,7 @@ bool __i915_request_submit(struct i915_request *request) > engine->serial++; > result = true; > > -xfer: /* We may be recursing from the signal callback of another i915 fence */ > - spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); > - > +xfer: > if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)) { > list_move_tail(&request->sched.link, &engine->active.requests); > clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags); > @@ -570,12 +568,19 @@ bool __i915_request_submit(struct i915_request *request) > } > GEM_BUG_ON(!llist_empty(&request->execute_cb)); > > - if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) && > - !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags) && > - !i915_request_enable_breadcrumb(request)) > - intel_engine_signal_breadcrumbs(engine); > + /* We may be recursing from the signal callback of another i915 fence */ > + if (!i915_request_signaled(request)) { > + spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); > + > + if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, > + &request->fence.flags) && > + !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, > + &request->fence.flags) && > + !i915_request_enable_breadcrumb(request)) > + intel_engine_signal_breadcrumbs(engine); Hmm. [ 68.742086] kworker/-32 3d.s4 65523842us : i915_request_enable_breadcrumb.cold: i915_request_enable_breadcrumb:345 GEM_BUG_ON(test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) So will take some massaging of i915_request_enable_breadcrumb() as well, at which point I wonder if we can remove the request->lock from here entirely. -Chris 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=-10.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 67175C433DF for ; Mon, 13 Jul 2020 13:28:11 +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 17744206F0 for ; Mon, 13 Jul 2020 13:28:11 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 17744206F0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=chris-wilson.co.uk 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 3738C8800B; Mon, 13 Jul 2020 13:28:10 +0000 (UTC) Received: from fireflyinternet.com (unknown [77.68.26.236]) by gabe.freedesktop.org (Postfix) with ESMTPS id F0F4B6E4EC for ; Mon, 13 Jul 2020 13:28:08 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from localhost (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP (TLS) id 21804017-1500050 for multiple; Mon, 13 Jul 2020 14:28:04 +0100 MIME-Version: 1.0 In-Reply-To: <20200713131738.21319-1-chris@chris-wilson.co.uk> References: <20200713131617.21175-1-chris@chris-wilson.co.uk> <20200713131738.21319-1-chris@chris-wilson.co.uk> From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Mon, 13 Jul 2020 14:28:04 +0100 Message-ID: <159464688483.23097.2677088254913725179@build.alporthouse.com> User-Agent: alot/0.9 Subject: Re: [Intel-gfx] [PATCH] drm/i915: Skip signaling a signaled 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: , Cc: "Nayana, Venkata Ramana" , stable@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Quoting Chris Wilson (2020-07-13 14:17:38) > Preempt-to-busy introduces various fascinating complications in that the > requests may complete as we are unsubmitting them from HW. As they may > then signal after unsubmission, we may find ourselves having to cleanup > the signaling request from within the signaling callback. This causes us > to recurse onto the same i915_request.lock. > > However, if the request is already signaled (as it will be before we > enter the signal callbacks), we know we can skip the signaling of that > request during submission, neatly evading the spinlock recursion. > > unsubmit(ve.rq0) # timeslice expiration or other preemption > -> virtual_submit_request(ve.rq0) > dma_fence_signal(ve.rq0) # request completed before preemption ack > -> submit_notify(ve.rq1) > -> virtual_submit_request(ve.rq1) # sees that we have completed ve.rq0 > -> __i915_request_submit(ve.rq0) > > [ 264.210142] BUG: spinlock recursion on CPU#2, sample_multi_tr/2093 > [ 264.210150] lock: 0xffff9efd6ac55080, .magic: dead4ead, .owner: sample_multi_tr/2093, .owner_cpu: 2 > [ 264.210155] CPU: 2 PID: 2093 Comm: sample_multi_tr Tainted: G U > [ 264.210158] Hardware name: Intel Corporation CoffeeLake Client Platform/CoffeeLake S UDIMM RVP, BIOS CNLSFWR1.R00.X212.B01.1909060036 09/06/2019 > [ 264.210160] Call Trace: > [ 264.210167] dump_stack+0x98/0xda > [ 264.210174] spin_dump.cold+0x24/0x3c > [ 264.210178] do_raw_spin_lock+0x9a/0xd0 > [ 264.210184] _raw_spin_lock_nested+0x6a/0x70 > [ 264.210314] __i915_request_submit+0x10a/0x3c0 [i915] > [ 264.210415] virtual_submit_request+0x9b/0x380 [i915] > [ 264.210516] submit_notify+0xaf/0x14c [i915] > [ 264.210602] __i915_sw_fence_complete+0x8a/0x230 [i915] > [ 264.210692] i915_sw_fence_complete+0x2d/0x40 [i915] > [ 264.210762] __dma_i915_sw_fence_wake+0x19/0x30 [i915] > [ 264.210767] dma_fence_signal_locked+0xb1/0x1c0 > [ 264.210772] dma_fence_signal+0x29/0x50 > [ 264.210871] i915_request_wait+0x5cb/0x830 [i915] > [ 264.210876] ? dma_resv_get_fences_rcu+0x294/0x5d0 > [ 264.210974] i915_gem_object_wait_fence+0x2f/0x40 [i915] > [ 264.211084] i915_gem_object_wait+0xce/0x400 [i915] > [ 264.211178] i915_gem_wait_ioctl+0xff/0x290 [i915] > > Signed-off-by: Chris Wilson > Fixes: 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy") > References: 6d06779e8672 ("drm/i915: Load balancing across a virtual engine") > Signed-off-by: Chris Wilson > Cc: Tvrtko Ursulin > Cc: "Nayana, Venkata Ramana" > Cc: # v5.4+ > --- > drivers/gpu/drm/i915/i915_request.c | 21 +++++++++++++-------- > 1 file changed, 13 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c > index 3bb7320249ae..9b74a1bea5db 100644 > --- a/drivers/gpu/drm/i915/i915_request.c > +++ b/drivers/gpu/drm/i915/i915_request.c > @@ -560,9 +560,7 @@ bool __i915_request_submit(struct i915_request *request) > engine->serial++; > result = true; > > -xfer: /* We may be recursing from the signal callback of another i915 fence */ > - spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); > - > +xfer: > if (!test_and_set_bit(I915_FENCE_FLAG_ACTIVE, &request->fence.flags)) { > list_move_tail(&request->sched.link, &engine->active.requests); > clear_bit(I915_FENCE_FLAG_PQUEUE, &request->fence.flags); > @@ -570,12 +568,19 @@ bool __i915_request_submit(struct i915_request *request) > } > GEM_BUG_ON(!llist_empty(&request->execute_cb)); > > - if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &request->fence.flags) && > - !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &request->fence.flags) && > - !i915_request_enable_breadcrumb(request)) > - intel_engine_signal_breadcrumbs(engine); > + /* We may be recursing from the signal callback of another i915 fence */ > + if (!i915_request_signaled(request)) { > + spin_lock_nested(&request->lock, SINGLE_DEPTH_NESTING); > + > + if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, > + &request->fence.flags) && > + !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, > + &request->fence.flags) && > + !i915_request_enable_breadcrumb(request)) > + intel_engine_signal_breadcrumbs(engine); Hmm. [ 68.742086] kworker/-32 3d.s4 65523842us : i915_request_enable_breadcrumb.cold: i915_request_enable_breadcrumb:345 GEM_BUG_ON(test_bit(I915_FENCE_FLAG_SIGNAL, &rq->fence.flags)) So will take some massaging of i915_request_enable_breadcrumb() as well, at which point I wonder if we can remove the request->lock from here entirely. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx