From patchwork Thu Jun 4 08:12:19 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 209627 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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 8E15EC433E8 for ; Thu, 4 Jun 2020 08:13:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E6D4207F9 for ; Thu, 4 Jun 2020 08:13:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="ifotk2PJ" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727902AbgFDIM5 (ORCPT ); Thu, 4 Jun 2020 04:12:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51504 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727829AbgFDIMu (ORCPT ); Thu, 4 Jun 2020 04:12:50 -0400 Received: from mail-wr1-x443.google.com (mail-wr1-x443.google.com [IPv6:2a00:1450:4864:20::443]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 09F5EC08C5C3 for ; Thu, 4 Jun 2020 01:12:50 -0700 (PDT) Received: by mail-wr1-x443.google.com with SMTP id l11so5071809wru.0 for ; Thu, 04 Jun 2020 01:12:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=zHLq9yPZgKKERQ/k46N5wAtq1tEa3e90dS7EqKAAVV8=; b=ifotk2PJMfPqXT/+gwn4eR7/3IWQV+W9DCcY7OyrRdaAZFQwKftRJdQXo0rpUM3/yB gFJrkbneOCQ2QX77TBZL8U/VuKVxgzOxX4tlg9WC2CbjGOvgEb6AVwmiQ15EpDYBd7lG Tzy0RTnpPG+HiMGAwz3SGe+WNdJdbJrdEf6D0= 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=zHLq9yPZgKKERQ/k46N5wAtq1tEa3e90dS7EqKAAVV8=; b=FVDb8iDNGB0ASbg0cdPEfaQcr9bNQ9Ep3WcpcH5n1DIk4t3SA5MOn3hsNhg8WXSPE/ aD/0tGCaMTi6ee5YB//JlHucscmoEum6me/36NhEuM/0Ut1H+FyDAPo9GHYg7wZOzoHa v8lMdsNvuScYg1CFYJeOiJ54q7KjBlKcXjX69QvtkZ7fK1HK0MJdOaRSIqXPvjrzplv1 s51CM9uTHUNyRRWgDvCgswMLx+HLflE0lJmnHNpInuNNrJpZrkaKnwG+5ZjWLRXZGzgI 831iC+sEWeost/4FaPE5HZDE5d7BROAsWAFdm4K2kJ1j9duSCSrigDNSEqaikWaKRDd8 M/mw== X-Gm-Message-State: AOAM530qMQ/lrvShZBHZMnm2jD3HBJec98nww5BWZXctN4liPAyeGZdK Be4CJCreshEfio+rkLbeZ2HM8Q== X-Google-Smtp-Source: ABdhPJwmXgxb0rRlbz9RyKT6KVGNFYaugD+jseyFJKYlXk9wNmaSF3eMQq44tjneQVcPWbVrYiOUJw== X-Received: by 2002:adf:fb0f:: with SMTP id c15mr3424740wrr.410.1591258368775; Thu, 04 Jun 2020 01:12:48 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id f11sm6873305wrj.2.2020.06.04.01.12.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 04 Jun 2020 01:12:48 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Intel Graphics Development , LKML , linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, Daniel Vetter , linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, Chris Wilson , Maarten Lankhorst , =?utf-8?q?Christian_K=C3=B6nig?= , Daniel Vetter Subject: [PATCH 13/18] drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail Date: Thu, 4 Jun 2020 10:12:19 +0200 Message-Id: <20200604081224.863494-14-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200604081224.863494-1-daniel.vetter@ffwll.ch> References: <20200604081224.863494-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org Trying to grab dma_resv_lock while in commit_tail before we've done all the code that leads to the eventual signalling of the vblank event (which can be a dma_fence) is deadlock-y. Don't do that. Here the solution is easy because just grabbing locks to read something races anyway. We don't need to bother, READ_ONCE is equivalent. And avoids the locking issue. Cc: linux-media@vger.kernel.org Cc: linaro-mm-sig@lists.linaro.org Cc: linux-rdma@vger.kernel.org Cc: amd-gfx@lists.freedesktop.org Cc: intel-gfx@lists.freedesktop.org Cc: Chris Wilson Cc: Maarten Lankhorst Cc: Christian König Signed-off-by: Daniel Vetter --- drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c index c575e7394d03..04c11443b9ca 100644 --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c @@ -6910,7 +6910,11 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state, * explicitly on fences instead * and in general should be called for * blocking commit to as per framework helpers + * + * Yes, this deadlocks, since you're calling dma_resv_lock in a + * path that leads to a dma_fence_signal(). Don't do that. */ +#if 0 r = amdgpu_bo_reserve(abo, true); if (unlikely(r != 0)) DRM_ERROR("failed to reserve buffer before flip\n"); @@ -6920,6 +6924,12 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state, tmz_surface = amdgpu_bo_encrypted(abo); amdgpu_bo_unreserve(abo); +#endif + /* + * this races anyway, so READ_ONCE isn't any better or worse + * than the stuff above. Except the stuff above can deadlock. + */ + tiling_flags = READ_ONCE(abo->tiling_flags); fill_dc_plane_info_and_addr( dm->adev, new_plane_state, tiling_flags,