From patchwork Wed Jun 9 21:29:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Jason Ekstrand X-Patchwork-Id: 12311251 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=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 A5321C48BCD for ; Wed, 9 Jun 2021 21:30:07 +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 54DF861009 for ; Wed, 9 Jun 2021 21:30:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 54DF861009 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=jlekstrand.net 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 F04FA6EB5A; Wed, 9 Jun 2021 21:30:06 +0000 (UTC) Received: from mail-pg1-x52f.google.com (mail-pg1-x52f.google.com [IPv6:2607:f8b0:4864:20::52f]) by gabe.freedesktop.org (Postfix) with ESMTPS id CCF3C6EB5A for ; Wed, 9 Jun 2021 21:30:05 +0000 (UTC) Received: by mail-pg1-x52f.google.com with SMTP id y11so12670906pgp.11 for ; Wed, 09 Jun 2021 14:30:05 -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:mime-version :content-transfer-encoding; bh=1g+3MSiw30ZUG53SUR1grNvQmYDXcp5mEMux+W2ItNw=; b=vXCl+inyLEoIZNXOX1L9adRQZG+kNIbgvotkaGq9RGmigo5n7saL4IVd9ZOxN89hYH TBOGbYjj+I5eq9jdvSxzZ9cwRjO8vhv5Wwy3VfKp8OHK3Gd98eFKbKn3Dtm51h3QVdAq mtMlZVlm2vAdXRu7VQrKU+3e+iTq20aQhmy03hJxbJB+jsFgbym/ntGHmMDWZVGkNST/ ykj0g8MzL9efrGa+7KzP5gcZcWwUrMPwx63EhOBx4/3cH0vpw2a0F/1A2+Li1O8mGEjH QTXGgweeEOOQTvMkqdWUhjiEzt4iPva7LKghMCjFcB+J+dFvbizQSphC2hSljbQ/A8Br gdJQ== 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:mime-version :content-transfer-encoding; bh=1g+3MSiw30ZUG53SUR1grNvQmYDXcp5mEMux+W2ItNw=; b=e8r+0vTwdRpuqEDfubCcNI0MhAV3GBS+t1K96Volb8+Gz/l/h+U0/ig4S9HGicMPLG K0srk//zORcsGU49gW8D/bpubjQqVr5PSz/FCIxO8vzB5VVSK7Hp9oMXCXFYy+OxA7nT Q4+oV63aAoKyLjScGB42T7aBUZP9nY181oCsiNgqsZCKd01GAnnOdtjtQGmj6KNpcm4j HiPNmK9+uTMeqGZuhtlTSXvfmrEERFuTjzaRXMw0hsWWC1X4vXyj0/05O/Afcz547vC8 8Ae9lSi6gXBuIsjI9VgK0j/x1Zz/QawizU2nr+Te893M+nCfTIYbJE4MQ4H97TwXEm91 +WZg== X-Gm-Message-State: AOAM532uR/GETLF/7l8H8GrLZCz5z3+oKbY8BbDATGbuTPYWSpOApKvn yXtVjtgxT/eqpmCqAl/numLBTQ== X-Google-Smtp-Source: ABdhPJyps0ZwxR2Raylp8ysOBVlLh4mI6IW82Q3LeixwleDYNNBLXjc30BQrEBjRRr78uyRQavcMrg== X-Received: by 2002:a05:6a00:2353:b029:2f2:987a:5da2 with SMTP id j19-20020a056a002353b02902f2987a5da2mr1742587pfj.58.1623274205229; Wed, 09 Jun 2021 14:30:05 -0700 (PDT) Received: from omlet.lan (jfdmzpr04-ext.jf.intel.com. [134.134.137.73]) by smtp.gmail.com with ESMTPSA id u14sm519133pjx.14.2021.06.09.14.30.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Jun 2021 14:30:04 -0700 (PDT) From: Jason Ekstrand To: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Date: Wed, 9 Jun 2021 16:29:54 -0500 Message-Id: <20210609212959.471209-1-jason@jlekstrand.net> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 Subject: [Intel-gfx] [PATCH 0/5] dma-fence, i915: Stop allowing SLAB_TYPESAFE_BY_RCU for dma_fence 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: Daniel Vetter , Matthew Auld , Dave Airlie , =?utf-8?q?Christian_K=C3=B6nig?= Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" Ever since 0eafec6d3244 ("drm/i915: Enable lockless lookup of request tracking via RCU"), the i915 driver has used SLAB_TYPESAFE_BY_RCU (it was called SLAB_DESTROY_BY_RCU at the time) in order to allow RCU on i915_request. As nifty as SLAB_TYPESAFE_BY_RCU may be, it comes with some serious disclaimers. In particular, objects can get recycled while RCU readers are still in-flight. This can be ok if everyone who touches these objects knows about the disclaimers and is careful. However, because we've chosen to use SLAB_TYPESAFE_BY_RCU for i915_request and because i915_request contains a dma_fence, we've leaked SLAB_TYPESAFE_BY_RCU and its whole pile of disclaimers to every driver in the kernel which may consume a dma_fence. We've tried to keep it somewhat contained by doing most of the hard work to prevent access of recycled objects via dma_fence_get_rcu_safe(). However, a quick grep of kernel sources says that, of the 30 instances of dma_fence_get_rcu*, only 11 of them use dma_fence_get_rcu_safe(). It's likely there bear traps in DRM and related subsystems just waiting for someone to accidentally step in them. This patch series stops us using SLAB_TYPESAFE_BY_RCU for i915_request and, instead, does an RCU-safe slab free via rcu_call(). This should let us keep most of the perf benefits of slab allocation while avoiding the bear traps inherent in SLAB_TYPESAFE_BY_RCU. It then removes support for SLAB_TYPESAFE_BY_RCU from dma_fence entirely. Note: The last patch is labled DONOTMERGE. This was at Daniel Vetter's request as we may want to let this bake for a couple releases before we rip out dma_fence_get_rcu_safe entirely. Signed-off-by: Jason Ekstrand Cc: Jon Bloomfield Cc: Daniel Vetter Cc: Christian König Cc: Dave Airlie Cc: Matthew Auld Cc: Maarten Lankhorst Jason Ekstrand (5): drm/i915: Move intel_engine_free_request_pool to i915_request.c drm/i915: Use a simpler scheme for caching i915_request drm/i915: Stop using SLAB_TYPESAFE_BY_RCU for i915_request dma-buf: Stop using SLAB_TYPESAFE_BY_RCU in selftests DONOTMERGE: dma-buf: Get rid of dma_fence_get_rcu_safe drivers/dma-buf/dma-fence-chain.c | 8 +- drivers/dma-buf/dma-resv.c | 4 +- drivers/dma-buf/st-dma-fence-chain.c | 24 +--- drivers/dma-buf/st-dma-fence.c | 27 +--- drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 4 +- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 8 -- drivers/gpu/drm/i915/i915_active.h | 4 +- drivers/gpu/drm/i915/i915_request.c | 147 ++++++++++++---------- drivers/gpu/drm/i915/i915_request.h | 2 - drivers/gpu/drm/i915/i915_vma.c | 4 +- include/drm/drm_syncobj.h | 4 +- include/linux/dma-fence.h | 50 -------- include/linux/dma-resv.h | 4 +- 13 files changed, 110 insertions(+), 180 deletions(-)