From patchwork Tue Mar 23 17:51:49 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jason Ekstrand X-Patchwork-Id: 12158901 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=-16.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 2052FC433DB for ; Tue, 23 Mar 2021 17:51:59 +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 CB84561585 for ; Tue, 23 Mar 2021 17:51:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CB84561585 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=jlekstrand.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id C0B7F6EB86; Tue, 23 Mar 2021 17:51:57 +0000 (UTC) Received: from mail-pj1-x102c.google.com (mail-pj1-x102c.google.com [IPv6:2607:f8b0:4864:20::102c]) by gabe.freedesktop.org (Postfix) with ESMTPS id E8CAF6EB86 for ; Tue, 23 Mar 2021 17:51:56 +0000 (UTC) Received: by mail-pj1-x102c.google.com with SMTP id ot17-20020a17090b3b51b0290109c9ac3c34so10251436pjb.4 for ; Tue, 23 Mar 2021 10:51:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=jlekstrand-net.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=md110hNLxE8dbTqk7pIPHacyxGQ+PjvjwqEzWKcViW0=; b=ZIZxRRzTvWobeJN1g4EdyhAYuTS/LLtnx74+m+0T0Sby8Jt+eK3xc8TlY1kjjGatC2 7bCxopZB5h1OB1Yd1cOcuzFy3/hY4X26AoPktioiKibE6Dt5L32W/LT2gAxNiJ3xAAqk T3jPeY/ZPKnhl3JNMDfno3NV3tDrp/C068KPtMrz2RxHb/rF6o1iJUtYL/WuRKtioahN UchCcK97bP8LWvHAJq2/6h9WsezkRX2nj/ki5+t4lbS41NAJHtrYhHQFWKTi9cPRIZO1 U/k0i0PEOPeokMRX9wjAfcBXzTyZk+W905ItbaLecugrRQd14eCAaVFHePRcPtQOv8Si aOdg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=md110hNLxE8dbTqk7pIPHacyxGQ+PjvjwqEzWKcViW0=; b=Q+QW/reBD/kRBIaMTzExaApg2lxiR5FTR+aqpC/AT2nRkQefw3MK25ADoIE4tPiXGx Df74TaFfg34CzhssS+xOTxrOchjjDvPdBveO4aJ+S4QHG6Zp/46K2270Hem49COejgi7 niSKiWFep09nvmpJP+920A4dMJApZwv1+0smyvhcybNAdQkgvX1Clahr0vAOeTRawmlF t6YlofOQ+YC8d7kfIJTsKIDGaFAniWtHqxK/iOHZSb1FHQCrO405YEpfAZyoAIlunbnW jV5PbvKsHQoGfPeZC8vdA+S9ZyGb1h6rvuY2vuMpFx/KrwGe4GkJbtefA3R1tBtRGfK1 lROA== X-Gm-Message-State: AOAM531GNkP+t5jFw7LIXEtvlVegDWRXrSjoTJ4I78dwmxW+jd8av7KT 7J3OrZ3M9QqblZUtpu3wLLKjPytOu/0odg== X-Google-Smtp-Source: ABdhPJzfu7Eqm9p860pc0s5n7+TyisD3h8Nuyx/7kpmSN6zmLrjx0Ej2JQb2SimMVHwJp6BLZQBvhA== X-Received: by 2002:a17:90a:c096:: with SMTP id o22mr5581792pjs.119.1616521916082; Tue, 23 Mar 2021 10:51:56 -0700 (PDT) Received: from omlet.com ([134.134.137.77]) by smtp.gmail.com with ESMTPSA id l25sm7977682pgu.72.2021.03.23.10.51.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Mar 2021 10:51:55 -0700 (PDT) From: Jason Ekstrand To: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Subject: [PATCH] drm/i915: Implement SINGLE_TIMELINE with a syncobj (v2) Date: Tue, 23 Mar 2021 12:51:49 -0500 Message-Id: <20210323175149.3390801-1-jason@jlekstrand.net> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20210319223856.2983244-5-jason@jlekstrand.net> References: <20210319223856.2983244-5-jason@jlekstrand.net> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Matthew Brost , Jason Ekstrand Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" This API is entirely unnecessary and I'd love to get rid of it. If userspace wants a single timeline across multiple contexts, they can either use implicit synchronization or a syncobj, both of which existed at the time this feature landed. The justification given at the time was that it would help GL drivers which are inherently single-timeline. However, neither of our GL drivers actually wanted the feature. i965 was already in maintenance mode at the time and iris uses syncobj for everything. Unfortunately, as much as I'd love to get rid of it, it is used by the media driver so we can't do that. We can, however, do the next-best thing which is to embed a syncobj in the context and do exactly what we'd expect from userspace internally. This isn't an entirely identical implementation because it's no longer atomic if userspace races with itself by calling execbuffer2 twice simultaneously from different threads. It won't crash in that case; it just doesn't guarantee any ordering between those two submits. Moving SINGLE_TIMELINE to a syncobj emulation has a couple of technical advantages beyond mere annoyance. One is that intel_timeline is no longer an api-visible object and can remain entirely an implementation detail. This may be advantageous as we make scheduler changes going forward. Second is that, together with deleting the CLONE_CONTEXT API, we should now have a 1:1 mapping between intel_context and intel_timeline which may help us reduce locking. v2 (Jason Ekstrand): - Update the comment on i915_gem_context::syncobj to mention that it's an emulation and the possible race if userspace calls execbuffer2 twice on the same context concurrently. - Wrap the checks for eb.gem_context->syncobj in unlikely() - Drop the dma_fence reference - Improved commit message Signed-off-by: Jason Ekstrand Cc: Maarten Lankhorst Cc: Matthew Brost Acked-by: Daniel Vetter --- drivers/gpu/drm/i915/gem/i915_gem_context.c | 47 ++++--------------- .../gpu/drm/i915/gem/i915_gem_context_types.h | 14 +++++- .../gpu/drm/i915/gem/i915_gem_execbuffer.c | 16 +++++++ 3 files changed, 39 insertions(+), 38 deletions(-) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index f88bac19333ec..e094f4a1ca4cd 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -67,6 +67,8 @@ #include #include +#include + #include "gt/gen6_ppgtt.h" #include "gt/intel_context.h" #include "gt/intel_engine_heartbeat.h" @@ -224,10 +226,6 @@ static void intel_context_set_gem(struct intel_context *ce, ce->vm = vm; } - GEM_BUG_ON(ce->timeline); - if (ctx->timeline) - ce->timeline = intel_timeline_get(ctx->timeline); - if (ctx->sched.priority >= I915_PRIORITY_NORMAL && intel_engine_has_timeslices(ce->engine)) __set_bit(CONTEXT_USE_SEMAPHORES, &ce->flags); @@ -344,8 +342,8 @@ void i915_gem_context_release(struct kref *ref) mutex_destroy(&ctx->engines_mutex); mutex_destroy(&ctx->lut_mutex); - if (ctx->timeline) - intel_timeline_put(ctx->timeline); + if (ctx->syncobj) + drm_syncobj_put(ctx->syncobj); put_pid(ctx->pid); mutex_destroy(&ctx->mutex); @@ -790,33 +788,11 @@ static void __assign_ppgtt(struct i915_gem_context *ctx, i915_vm_close(vm); } -static void __set_timeline(struct intel_timeline **dst, - struct intel_timeline *src) -{ - struct intel_timeline *old = *dst; - - *dst = src ? intel_timeline_get(src) : NULL; - - if (old) - intel_timeline_put(old); -} - -static void __apply_timeline(struct intel_context *ce, void *timeline) -{ - __set_timeline(&ce->timeline, timeline); -} - -static void __assign_timeline(struct i915_gem_context *ctx, - struct intel_timeline *timeline) -{ - __set_timeline(&ctx->timeline, timeline); - context_apply_all(ctx, __apply_timeline, timeline); -} - static struct i915_gem_context * i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags) { struct i915_gem_context *ctx; + int ret; if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE && !HAS_EXECLISTS(i915)) @@ -845,16 +821,13 @@ i915_gem_create_context(struct drm_i915_private *i915, unsigned int flags) } if (flags & I915_CONTEXT_CREATE_FLAGS_SINGLE_TIMELINE) { - struct intel_timeline *timeline; - - timeline = intel_timeline_create(&i915->gt); - if (IS_ERR(timeline)) { + ret = drm_syncobj_create(&ctx->syncobj, + DRM_SYNCOBJ_CREATE_SIGNALED, + NULL); + if (ret) { context_close(ctx); - return ERR_CAST(timeline); + return ERR_PTR(ret); } - - __assign_timeline(ctx, timeline); - intel_timeline_put(timeline); } trace_i915_context_create(ctx); diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h index 676592e27e7d2..df76767f0c41b 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h +++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h @@ -83,7 +83,19 @@ struct i915_gem_context { struct i915_gem_engines __rcu *engines; struct mutex engines_mutex; /* guards writes to engines */ - struct intel_timeline *timeline; + /** + * @syncobj: Shared timeline syncobj + * + * When the SHARED_TIMELINE flag is set on context creation, we + * emulate a single timeline across all engines using this syncobj. + * For every execbuffer2 call, this syncobj is used as both an in- + * and out-fence. Unlike the real intel_timeline, this doesn't + * provide perfect atomic in-order guarantees if the client races + * with itself by calling execbuffer2 twice concurrently. However, + * if userspace races with itself, that's not likely to yield well- + * defined results anyway so we choose to not care. + */ + struct drm_syncobj *syncobj; /** * @vm: unique address space (GTT) diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c index 96403130a373d..2e9748c1edddf 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c @@ -3295,6 +3295,16 @@ i915_gem_do_execbuffer(struct drm_device *dev, goto err_vma; } + if (unlikely(eb.gem_context->syncobj)) { + struct dma_fence *fence; + + fence = drm_syncobj_fence_get(eb.gem_context->syncobj); + err = i915_request_await_dma_fence(eb.request, fence); + if (err) + goto err_ext; + dma_fence_put(fence); + } + if (in_fence) { if (args->flags & I915_EXEC_FENCE_SUBMIT) err = i915_request_await_execution(eb.request, @@ -3351,6 +3361,12 @@ i915_gem_do_execbuffer(struct drm_device *dev, fput(out_fence->file); } } + + if (unlikely(eb.gem_context->syncobj)) { + drm_syncobj_replace_fence(eb.gem_context->syncobj, + &eb.request->fence); + } + i915_request_put(eb.request); err_vma: