From patchwork Wed Apr 8 16:24:03 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11480541 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0C1C981 for ; Wed, 8 Apr 2020 16:24:16 +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 DEFD320784 for ; Wed, 8 Apr 2020 16:24:15 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="HYp5Bq75" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DEFD320784 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch 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 5F2C66EA9D; Wed, 8 Apr 2020 16:24:12 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-wm1-x343.google.com (mail-wm1-x343.google.com [IPv6:2a00:1450:4864:20::343]) by gabe.freedesktop.org (Postfix) with ESMTPS id 60AD96EA96 for ; Wed, 8 Apr 2020 16:24:11 +0000 (UTC) Received: by mail-wm1-x343.google.com with SMTP id h2so44239wmb.4 for ; Wed, 08 Apr 2020 09:24:11 -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:mime-version :content-transfer-encoding; bh=o1wXXAbri86QChEa50j3H0JwCub+mO1ccJpn2usVHv0=; b=HYp5Bq75xxTmKkQ+MwniWHFEFiXu9DoFPzIjKWs0sTP35Z4+14iO0Ez2Itb5g6Yzf4 gGIW60ImXzKzNMVCeZNeLLmoYyzc/2bSB490taxtJsRyvN1rr5hsDcDs/Kxz6UI/Zg/g PLn57TkhnsaZH3nq26pN7Agbq8A8eE+yjcgoU= 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=o1wXXAbri86QChEa50j3H0JwCub+mO1ccJpn2usVHv0=; b=tlqnz58avMOZfuGTh5XriNnAqqnTOoW6ua8OsX4ayerN5ZoLhDUrpP8KuL4sMy55m3 XJdGH2hMnNenk9Bitf340ACaTIyhXUvigAtt5jf4VVzh6QByxTXhTbRy8ayQW0V1TJHG 4Fb+DwjY7a8v0jc0lenFqhmpWoCy8bvcA+G6Izv3plA17ZyTwGq16pOZOT0cw8bQcI2Y LjqXdC5bjg8NaAWXMMcsS9+5E823bfdLMMZfj7nE4FHqzlpi7K5mrz+nWiLQnHfusA+6 VDQQe3JL7VAmvbYqYTdwVQ5GdAh/zkF26WNzBxHTZthn6XET6bvTdCp94fU8PNESuy4i 1TPw== X-Gm-Message-State: AGi0Pub2qZea/b2Xebbn3vtkwj2BzPDW2ey/JWJ9EIY/RyqQpYIEJ7O6 4jqDhkll4Cpn16RUZf7aE7WeTbEjbMU= X-Google-Smtp-Source: APiQypKz8wOvsiwaQ6yZhKkaOvbAB1KfIjZ7OheWj1K9qwQtTAOpdj5ga9Ksu7zXCCdYCbGmsA9ZIg== X-Received: by 2002:a1c:7ed0:: with SMTP id z199mr5427573wmc.60.1586363049729; Wed, 08 Apr 2020 09:24:09 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id m15sm47369wmc.35.2020.04.08.09.24.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Apr 2020 09:24:08 -0700 (PDT) From: Daniel Vetter To: DRI Development Subject: [PATCH] drm: avoid spurious EBUSY due to nonblocking atomic modesets Date: Wed, 8 Apr 2020 18:24:03 +0200 Message-Id: <20200408162403.3616785-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.25.1 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: Daniel Stone , Daniel Vetter , Intel Graphics Development , stable@vger.kernel.org, Daniel Vetter , Pekka Paalanen Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" When doing an atomic modeset with ALLOW_MODESET drivers are allowed to pull in arbitrary other resources, including CRTCs (e.g. when reconfiguring global resources). But in nonblocking mode userspace has then no idea this happened, which can lead to spurious EBUSY calls, both: - when that other CRTC is currently busy doing a page_flip the ALLOW_MODESET commit can fail with an EBUSY - on the other CRTC a normal atomic flip can fail with EBUSY because of the additional commit inserted by the kernel without userspace's knowledge For blocking commits this isn't a problem, because everyone else will just block until all the CRTC are reconfigured. Only thing userspace can notice is the dropped frames without any reason for why frames got dropped. Consensus is that we need new uapi to handle this properly, but no one has any idea what exactly the new uapi should look like. As a stop-gap plug this problem by demoting nonblocking commits which might cause issues by including CRTCs not in the original request to blocking commits. v2: Add comments and a WARN_ON to enforce this only when allowed - we don't want to silently convert page flips into blocking plane updates just because the driver is buggy. v3: Fix inverted WARN_ON (Pekka). References: https://lists.freedesktop.org/archives/dri-devel/2018-July/182281.html Bugzilla: https://gitlab.freedesktop.org/wayland/weston/issues/24#note_9568 Cc: Daniel Stone Cc: Pekka Paalanen Cc: stable@vger.kernel.org Reviewed-by: Daniel Stone Cc: Ville Syrjälä Signed-off-by: Daniel Vetter --- Resending because last attempt failed CI and meanwhile the results are lost :-/ -Daniel --- drivers/gpu/drm/drm_atomic.c | 34 +++++++++++++++++++++++++++++++--- 1 file changed, 31 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index 965173fd0ac2..4f140ff6fb98 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1362,15 +1362,43 @@ EXPORT_SYMBOL(drm_atomic_commit); int drm_atomic_nonblocking_commit(struct drm_atomic_state *state) { struct drm_mode_config *config = &state->dev->mode_config; - int ret; + unsigned requested_crtc = 0; + unsigned affected_crtc = 0; + struct drm_crtc *crtc; + struct drm_crtc_state *crtc_state; + bool nonblocking = true; + int ret, i; + + /* + * For commits that allow modesets drivers can add other CRTCs to the + * atomic commit, e.g. when they need to reallocate global resources. + * + * But when userspace also requests a nonblocking commit then userspace + * cannot know that the commit affects other CRTCs, which can result in + * spurious EBUSY failures. Until we have better uapi plug this by + * demoting such commits to blocking mode. + */ + for_each_new_crtc_in_state(state, crtc, crtc_state, i) + requested_crtc |= drm_crtc_mask(crtc); ret = drm_atomic_check_only(state); if (ret) return ret; - DRM_DEBUG_ATOMIC("committing %p nonblocking\n", state); + for_each_new_crtc_in_state(state, crtc, crtc_state, i) + affected_crtc |= drm_crtc_mask(crtc); + + if (affected_crtc != requested_crtc) { + /* adding other CRTC is only allowed for modeset commits */ + WARN_ON(!state->allow_modeset); + + DRM_DEBUG_ATOMIC("demoting %p to blocking mode to avoid EBUSY\n", state); + nonblocking = false; + } else { + DRM_DEBUG_ATOMIC("committing %p nonblocking\n", state); + } - return config->funcs->atomic_commit(state->dev, state, true); + return config->funcs->atomic_commit(state->dev, state, nonblocking); } EXPORT_SYMBOL(drm_atomic_nonblocking_commit);