From patchwork Mon Nov 28 22:31:04 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Anholt X-Patchwork-Id: 9450639 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 833736071C for ; Mon, 28 Nov 2016 22:31:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 739BE28047 for ; Mon, 28 Nov 2016 22:31:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 64EE5280B0; Mon, 28 Nov 2016 22:31:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.2 required=2.0 tests=BAYES_00, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id C349928047 for ; Mon, 28 Nov 2016 22:31:09 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id CD6B16E5FB; Mon, 28 Nov 2016 22:31:07 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from anholt.net (anholt.net [50.246.234.109]) by gabe.freedesktop.org (Postfix) with ESMTP id E8ADA6E5FB for ; Mon, 28 Nov 2016 22:31:05 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by anholt.net (Postfix) with ESMTP id B40A610A21D8; Mon, 28 Nov 2016 22:35:08 -0800 (PST) X-Virus-Scanned: Debian amavisd-new at anholt.net Received: from anholt.net ([127.0.0.1]) by localhost (kingsolver.anholt.net [127.0.0.1]) (amavisd-new, port 10024) with LMTP id DYSVrtmz0LTb; Mon, 28 Nov 2016 22:35:07 -0800 (PST) Received: from eliezer.anholt.net (localhost [127.0.0.1]) by anholt.net (Postfix) with ESMTP id 807D510A1CFC; Mon, 28 Nov 2016 22:35:07 -0800 (PST) Received: by eliezer.anholt.net (Postfix, from userid 1000) id 206FB2E0314; Mon, 28 Nov 2016 14:31:04 -0800 (PST) From: Eric Anholt To: dri-devel@lists.freedesktop.org Subject: [PATCH] drm/vc4: Fix race between page flip completion event and clean-up Date: Mon, 28 Nov 2016 14:31:04 -0800 Message-Id: <20161128223104.28645-1-eric@anholt.net> X-Mailer: git-send-email 2.10.2 Cc: Derek Foreman , linux-kernel@vger.kernel.org X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP From: Derek Foreman There was a small window where a userspace program could submit a pageflip after receiving a pageflip completion event yet still receive EBUSY. Signed-off-by: Derek Foreman Signed-off-by: Eric Anholt Reviewed-by: Eric Anholt Reviewed-by: Daniel Stone --- drivers/gpu/drm/vc4/vc4_crtc.c | 8 ++++++++ drivers/gpu/drm/vc4/vc4_drv.h | 1 + drivers/gpu/drm/vc4/vc4_kms.c | 33 +++++++++++++++++++++++++-------- 3 files changed, 34 insertions(+), 8 deletions(-) diff --git a/drivers/gpu/drm/vc4/vc4_crtc.c b/drivers/gpu/drm/vc4/vc4_crtc.c index 7f08d681a74b..82f914af4156 100644 --- a/drivers/gpu/drm/vc4/vc4_crtc.c +++ b/drivers/gpu/drm/vc4/vc4_crtc.c @@ -669,6 +669,14 @@ void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id) CRTC_WRITE(PV_INTEN, 0); } +/* Must be called with the event lock held */ +bool vc4_event_pending(struct drm_crtc *crtc) +{ + struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc); + + return !!vc4_crtc->event; +} + static void vc4_crtc_handle_page_flip(struct vc4_crtc *vc4_crtc) { struct drm_crtc *crtc = &vc4_crtc->base; diff --git a/drivers/gpu/drm/vc4/vc4_drv.h b/drivers/gpu/drm/vc4/vc4_drv.h index fef172804345..b3064e2e79c1 100644 --- a/drivers/gpu/drm/vc4/vc4_drv.h +++ b/drivers/gpu/drm/vc4/vc4_drv.h @@ -442,6 +442,7 @@ int vc4_bo_stats_debugfs(struct seq_file *m, void *arg); extern struct platform_driver vc4_crtc_driver; int vc4_enable_vblank(struct drm_device *dev, unsigned int crtc_id); void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id); +bool vc4_event_pending(struct drm_crtc *crtc); int vc4_crtc_debugfs_regs(struct seq_file *m, void *arg); int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id, unsigned int flags, int *vpos, int *hpos, diff --git a/drivers/gpu/drm/vc4/vc4_kms.c b/drivers/gpu/drm/vc4/vc4_kms.c index c1f65c6c8e60..67af2af70af0 100644 --- a/drivers/gpu/drm/vc4/vc4_kms.c +++ b/drivers/gpu/drm/vc4/vc4_kms.c @@ -119,17 +119,34 @@ static int vc4_atomic_commit(struct drm_device *dev, /* Make sure that any outstanding modesets have finished. */ if (nonblock) { - ret = down_trylock(&vc4->async_modeset); - if (ret) { + struct drm_crtc *crtc; + struct drm_crtc_state *crtc_state; + unsigned long flags; + bool busy = false; + + /* + * If there's an undispatched event to send then we're + * obviously still busy. If there isn't, then we can + * unconditionally wait for the semaphore because it + * shouldn't be contended (for long). + * + * This is to prevent a race where queuing a new flip + * from userspace immediately on receipt of an event + * beats our clean-up and returns EBUSY. + */ + spin_lock_irqsave(&dev->event_lock, flags); + for_each_crtc_in_state(state, crtc, crtc_state, i) + busy |= vc4_event_pending(crtc); + spin_unlock_irqrestore(&dev->event_lock, flags); + if (busy) { kfree(c); return -EBUSY; } - } else { - ret = down_interruptible(&vc4->async_modeset); - if (ret) { - kfree(c); - return ret; - } + } + ret = down_interruptible(&vc4->async_modeset); + if (ret) { + kfree(c); + return ret; } ret = drm_atomic_helper_prepare_planes(dev, state);