From patchwork Tue May 3 09:12:31 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Maarten Lankhorst X-Patchwork-Id: 9001251 Return-Path: X-Original-To: patchwork-dri-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id AB4E5BF29F for ; Tue, 3 May 2016 09:12:51 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 37F9E2025A for ; Tue, 3 May 2016 09:12:46 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) by mail.kernel.org (Postfix) with ESMTP id 6817720148 for ; Tue, 3 May 2016 09:12:45 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 71C2A6E6E8; Tue, 3 May 2016 09:12:41 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mblankhorst.nl (mblankhorst.nl [IPv6:2a02:2308::216:3eff:fe92:dfa3]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3E0E66E6E7; Tue, 3 May 2016 09:12:39 +0000 (UTC) From: Maarten Lankhorst To: dri-devel@lists.freedesktop.org Subject: [PATCH] drm/atomic: Add WARN_ON when state->acquire_ctx is not set. Date: Tue, 3 May 2016 11:12:31 +0200 Message-Id: <1462266751-29123-1-git-send-email-maarten.lankhorst@linux.intel.com> X-Mailer: git-send-email 2.5.5 Cc: intel-gfx@lists.freedesktop.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-Spam-Status: No, score=-5.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP When I was writing an atomic wrapper for rmfb, I ran into the following backtrace from lockdep: ============================================= [ INFO: possible recursive locking detected ] 4.5.0-patser+ #4696 Tainted: G U --------------------------------------------- kworker/2:2/2608 is trying to acquire lock: (crtc_ww_class_mutex){+.+.+.}, at: [] drm_modeset_lock+0x7c/0x120 [drm] but task is already holding lock: (crtc_ww_class_mutex){+.+.+.}, at: [] modeset_backoff+0x8d/0x220 [drm] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(crtc_ww_class_mutex); lock(crtc_ww_class_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by kworker/2:2/2608: #0: ("events"){.+.+.+}, at: [] process_one_work+0x15a/0x6c0 #1: ((&arg.work)){+.+.+.}, at: [] process_one_work+0x15a/0x6c0 #2: (crtc_ww_class_acquire){+.+.+.}, at: [] drm_atomic_helper_remove_fb+0x4a/0x1d0 [drm_kms_helper] #3: (crtc_ww_class_mutex){+.+.+.}, at: [] modeset_backoff+0x8d/0x220 [drm] While lockdep probably catches this bug when it happens, it's better to explicitly warn when state->acquire_ctx is not set. Signed-off-by: Maarten Lankhorst --- drivers/gpu/drm/drm_atomic.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index 0b526423f19f..69adcf3944cc 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -263,6 +263,8 @@ drm_atomic_get_crtc_state(struct drm_atomic_state *state, int ret, index = drm_crtc_index(crtc); struct drm_crtc_state *crtc_state; + WARN_ON(!state->acquire_ctx); + crtc_state = drm_atomic_get_existing_crtc_state(state, crtc); if (crtc_state) return crtc_state; @@ -622,6 +624,8 @@ drm_atomic_get_plane_state(struct drm_atomic_state *state, int ret, index = drm_plane_index(plane); struct drm_plane_state *plane_state; + WARN_ON(!state->acquire_ctx); + plane_state = drm_atomic_get_existing_plane_state(state, plane); if (plane_state) return plane_state; @@ -890,6 +894,8 @@ drm_atomic_get_connector_state(struct drm_atomic_state *state, struct drm_mode_config *config = &connector->dev->mode_config; struct drm_connector_state *connector_state; + WARN_ON(!state->acquire_ctx); + ret = drm_modeset_lock(&config->connection_mutex, state->acquire_ctx); if (ret) return ERR_PTR(ret);