From patchwork Tue Jun 11 11:57:16 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Thomas Zimmermann X-Patchwork-Id: 10986671 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 380CB14BB for ; Tue, 11 Jun 2019 11:57:40 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 27D81287E6 for ; Tue, 11 Jun 2019 11:57:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 1BFC4287B4; Tue, 11 Jun 2019 11:57:40 +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=-5.2 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 A71A728450 for ; Tue, 11 Jun 2019 11:57:39 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 90E99891B8; Tue, 11 Jun 2019 11:57:37 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mx1.suse.de (mx2.suse.de [195.135.220.15]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3C8A1891B8 for ; Tue, 11 Jun 2019 11:57:36 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B59A5AEC3; Tue, 11 Jun 2019 11:57:34 +0000 (UTC) From: Thomas Zimmermann To: noralf@tronnes.org, sam@ravnborg.org, daniel@ffwll.ch Subject: [PATCH] drm: Reverse lock order in pan_display_legacy() Date: Tue, 11 Jun 2019 13:57:16 +0200 Message-Id: <20190611115716.7052-1-tzimmermann@suse.de> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Zimmermann , dri-devel@lists.freedesktop.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" X-Virus-Scanned: ClamAV using ClamSMTP Acquiring drm_client_dev.modeset_mutex after the locks in drm_fb_helper.dev creates a deadlock with drm_setup_crtcs() as shown below: [ 4.959319] fbcon: radeondrmfb (fb0) is primary device [ 4.993952] Console: switching to colour frame buffer device 240x67 [ 4.994040] [ 4.994041] ====================================================== [ 4.994041] WARNING: possible circular locking dependency detected [ 4.994042] 5.2.0-rc4-1-default+ #39 Tainted: G E [ 4.994043] ------------------------------------------------------ [ 4.994043] systemd-udevd/369 is trying to acquire lock: [ 4.994044] 00000000fb622acb (&client->modeset_mutex){+.+.}, at: drm_fb_helper_pan_display+0x103/0x1f0 [drm_kms_helper] [ 4.994055] [ 4.994055] but task is already holding lock: [ 4.994055] 0000000028767ae4 (crtc_ww_class_mutex){+.+.}, at: drm_modeset_lock+0x42/0xf0 [drm] [ 4.994072] [ 4.994072] which lock already depends on the new lock. [ 4.994072] [ 4.994072] [ 4.994072] the existing dependency chain (in reverse order) is: [ 4.994073] [ 4.994073] -> #3 (crtc_ww_class_mutex){+.+.}: [ 4.994076] lock_acquire+0x9e/0x170 [ 4.994079] __ww_mutex_lock.constprop.18+0x97/0xf40 [ 4.994080] ww_mutex_lock+0x30/0x90 [ 4.994091] drm_modeset_lock+0x42/0xf0 [drm] [ 4.994102] drm_modeset_lock_all_ctx+0x1f/0xe0 [drm] [ 4.994113] drm_modeset_lock_all+0x5e/0x1a0 [drm] [ 4.994163] intel_modeset_init+0x60b/0xda0 [i915] .. [ 4.994253] [ 4.994253] -> #2 (crtc_ww_class_acquire){+.+.}: [ 4.994255] lock_acquire+0x9e/0x170 [ 4.994270] drm_modeset_acquire_init+0xcc/0x100 [drm] [ 4.994280] drm_modeset_lock_all+0x44/0x1a0 [drm] [ 4.994320] intel_modeset_init+0x60b/0xda0 [i915] .. [ 4.994403] [ 4.994403] -> #1 (&dev->mode_config.mutex){+.+.}: [ 4.994405] lock_acquire+0x9e/0x170 [ 4.994408] __mutex_lock+0x62/0x8c0 [ 4.994413] drm_setup_crtcs+0x17c/0xc50 [drm_kms_helper] [ 4.994418] __drm_fb_helper_initial_config_and_unlock+0x34/0x530 [drm_kms_helper] [ 4.994450] radeon_fbdev_init+0x110/0x130 [radeon] .. [ 4.994535] [ 4.994535] -> #0 (&client->modeset_mutex){+.+.}: [ 4.994537] __lock_acquire+0xa85/0xe90 [ 4.994538] lock_acquire+0x9e/0x170 [ 4.994540] __mutex_lock+0x62/0x8c0 [ 4.994545] drm_fb_helper_pan_display+0x103/0x1f0 [drm_kms_helper] [ 4.994547] fb_pan_display+0x92/0x120 [ 4.994549] bit_update_start+0x1a/0x40 [ 4.994550] fbcon_switch+0x392/0x580 [ 4.994552] redraw_screen+0x12c/0x220 [ 4.994553] do_bind_con_driver.cold.30+0xe1/0x10d [ 4.994554] do_take_over_console+0x113/0x190 [ 4.994555] do_fbcon_takeover+0x58/0xb0 [ 4.994557] notifier_call_chain+0x47/0x70 [ 4.994558] blocking_notifier_call_chain+0x44/0x60 [ 4.994559] register_framebuffer+0x231/0x310 [ 4.994564] __drm_fb_helper_initial_config_and_unlock+0x2fd/0x530 [drm_kms_helper] [ 4.994590] radeon_fbdev_init+0x110/0x130 [radeon] .. This problem was introduced in d81294afe drm/fb-helper: Remove drm_fb_helper_crtc Reversing the lock ordering in pan_display_legacy() fixes the issue. The fix was suggested by Daniel Vetter. Signed-off-by: Thomas Zimmermann Fixes: d81294afeecdacc8d84804ba0bcb3d39e64d0f27 Acked-by: Noralf Trønnes --- drivers/gpu/drm/drm_fb_helper.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 7b388674a456..d6991f07cb17 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -1586,8 +1586,8 @@ static int pan_display_legacy(struct fb_var_screeninfo *var, struct drm_mode_set *modeset; int ret = 0; - drm_modeset_lock_all(fb_helper->dev); mutex_lock(&client->modeset_mutex); + drm_modeset_lock_all(fb_helper->dev); drm_client_for_each_modeset(modeset, client) { modeset->x = var->xoffset; modeset->y = var->yoffset; @@ -1600,8 +1600,8 @@ static int pan_display_legacy(struct fb_var_screeninfo *var, } } } - mutex_unlock(&client->modeset_mutex); drm_modeset_unlock_all(fb_helper->dev); + mutex_unlock(&client->modeset_mutex); return ret; }