From patchwork Mon Jul 12 04:35:04 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Desmond Cheong Zhi Xi X-Patchwork-Id: 12370167 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=-13.5 required=3.0 tests=BAYES_00, DKIM_ADSP_CUSTOM_MED,DKIM_INVALID,DKIM_SIGNED,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,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 346A1C07E9B for ; Mon, 12 Jul 2021 04:35:58 +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 D589C60FF1 for ; Mon, 12 Jul 2021 04:35:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D589C60FF1 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com 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 350A089BC0; Mon, 12 Jul 2021 04:35:57 +0000 (UTC) Received: from mail-pf1-x432.google.com (mail-pf1-x432.google.com [IPv6:2607:f8b0:4864:20::432]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7B49189BC0; Mon, 12 Jul 2021 04:35:56 +0000 (UTC) Received: by mail-pf1-x432.google.com with SMTP id 17so15241619pfz.4; Sun, 11 Jul 2021 21:35:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=vc5xi5ftWnxZlU1gt0+b48wT38LyZFngC4JD9PKuX7I=; b=Cb3M3vkk3FuoDtvFBvEh8156faQwTUThdp+n0uUYWQBYv3ouu9t5ZNGd5SwrKX67Kt vl0hi9W3WmsJuZDYRTmIOr+4DeklTVF04l28vjLZf5qufrBH0FT1YD5Pslug4BG3Wtoe 8AkwcOysJKQ6LzJP7JdbshGQu2qBgqICEslwnsXZ8jA0qGT1eqQko7RbSSIeNPZ0Wg4k HH6HAbsBVycseDYivQSwfVgRRi5N2iUJFGEcs38O1flBvrS0sNwNE4s7mek9uJCX67nY vZlOk9uRf2EmQ82ji96k3z3Z44BH3NKnBA78PtKalqTnCAMqh7uHRPCe7v3VojaTKZGx PGMQ== 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=vc5xi5ftWnxZlU1gt0+b48wT38LyZFngC4JD9PKuX7I=; b=TlGyg+PJAQrqDNbIwYkwQybzadtDXFeZ18FrHjlSBx/jiU845iXyy6fqcsue1KYx/t r5CX+sxqxRZqeS1gf9Kum+RTh7NKHltOU98EfOFblqhw3OBq3frp3CWWAVTlAWoH7dWs X6QVW8VDyIit6ojU0k/5+c2fZv8a/vIaayfrJLhVYBodUnyhrAuygb3X2Lk1+3G9/WUz ybVPojCmOvj91oKD6Sb+6A45E27NTzVnt11/2ah5Tv3oWtco6V71LvylWa+6KE0+w7xD PKuqWOUfmYrjBujxDpdXEzkphEp2QbGMskBpQdU8+n6EIELUzkX3Zw2HoLMoUsqkVgxG Xu6w== X-Gm-Message-State: AOAM5309lXGXwxPUzvcHu7UHClMCDzBPn3hWnkzQlR7Cq+F71Uwek2Le Z03YzDYfI5KAgG0OxCr8z/0= X-Google-Smtp-Source: ABdhPJxCujRkDQjCW3B0eNy7eTGjw4nq7M1Kn3DT88JRrgd3WhjryI26Pk/IICRmxm9iWx/UrR5ZbA== X-Received: by 2002:a63:f241:: with SMTP id d1mr2270900pgk.424.1626064556049; Sun, 11 Jul 2021 21:35:56 -0700 (PDT) Received: from localhost.localdomain ([118.200.190.93]) by smtp.gmail.com with ESMTPSA id n3sm14242764pfn.216.2021.07.11.21.35.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Jul 2021 21:35:55 -0700 (PDT) From: Desmond Cheong Zhi Xi To: maarten.lankhorst@linux.intel.com, mripard@kernel.org, tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch, sumit.semwal@linaro.org, christian.koenig@amd.com Subject: [PATCH v8 1/5] drm: avoid circular locks in drm_mode_getconnector Date: Mon, 12 Jul 2021 12:35:04 +0800 Message-Id: <20210712043508.11584-2-desmondcheongzx@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210712043508.11584-1-desmondcheongzx@gmail.com> References: <20210712043508.11584-1-desmondcheongzx@gmail.com> 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 Vetter , gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, emil.l.velikov@gmail.com, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org, linux-media@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" In preparation for a future patch to take a lock on drm_device.master_mutex inside drm_is_current_master(), we first move the call to drm_is_current_master() in drm_mode_getconnector out from the section locked by &dev->mode_config.mutex. This avoids creating a circular lock dependency. Failing to avoid this lock dependency produces the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc7-CI-CI_DRM_10254+ #1 Not tainted ------------------------------------------------------ kms_frontbuffer/1087 is trying to acquire lock: ffff88810dcd01a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_is_current_master+0x1b/0x40 but task is already holding lock: ffff88810dcd0488 (&dev->mode_config.mutex){+.+.}-{3:3}, at: drm_mode_getconnector+0x1c6/0x4a0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&dev->mode_config.mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_probe+0x22e/0xca0 __drm_fb_helper_initial_config_and_unlock+0x42/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #1 (&client->modeset_mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_commit_locked+0x1c/0x180 drm_client_modeset_commit+0x1c/0x40 __drm_fb_helper_restore_fbdev_mode_unlocked+0x88/0xb0 drm_fb_helper_set_par+0x34/0x40 intel_fbdev_set_par+0x11/0x40 [i915] fbcon_init+0x270/0x4f0 visual_init+0xc6/0x130 do_bind_con_driver+0x1e5/0x2d0 do_take_over_console+0x10e/0x180 do_fbcon_takeover+0x53/0xb0 register_framebuffer+0x22d/0x310 __drm_fb_helper_initial_config_and_unlock+0x36c/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #0 (&dev->master_mutex){+.+.}-{3:3}: __lock_acquire+0x151e/0x2590 lock_acquire+0xd1/0x3d0 __mutex_lock+0xab/0x970 drm_is_current_master+0x1b/0x40 drm_mode_getconnector+0x37e/0x4a0 drm_ioctl_kernel+0xa8/0xf0 drm_ioctl+0x1e8/0x390 __x64_sys_ioctl+0x6a/0xa0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: &dev->master_mutex --> &client->modeset_mutex --> &dev->mode_config.mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev->mode_config.mutex); lock(&client->modeset_mutex); lock(&dev->mode_config.mutex); lock(&dev->master_mutex); *** DEADLOCK *** 1 lock held by kms_frontbuffer/1087: #0: ffff88810dcd0488 (&dev->mode_config.mutex){+.+.}-{3:3}, at: drm_mode_getconnector+0x1c6/0x4a0 stack backtrace: CPU: 7 PID: 1087 Comm: kms_frontbuffer Not tainted 5.13.0-rc7-CI-CI_DRM_10254+ #1 Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3234.A01.1906141750 06/14/2019 Call Trace: dump_stack+0x7f/0xad check_noncircular+0x12e/0x150 __lock_acquire+0x151e/0x2590 lock_acquire+0xd1/0x3d0 __mutex_lock+0xab/0x970 drm_is_current_master+0x1b/0x40 drm_mode_getconnector+0x37e/0x4a0 drm_ioctl_kernel+0xa8/0xf0 drm_ioctl+0x1e8/0x390 __x64_sys_ioctl+0x6a/0xa0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae Reported-by: Daniel Vetter Signed-off-by: Desmond Cheong Zhi Xi Reviewed-by: Emil Velikov --- drivers/gpu/drm/drm_connector.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c index da39e7ff6965..2ba257b1ae20 100644 --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -2414,6 +2414,7 @@ int drm_mode_getconnector(struct drm_device *dev, void *data, struct drm_mode_modeinfo u_mode; struct drm_mode_modeinfo __user *mode_ptr; uint32_t __user *encoder_ptr; + bool is_current_master; if (!drm_core_check_feature(dev, DRIVER_MODESET)) return -EOPNOTSUPP; @@ -2444,9 +2445,11 @@ int drm_mode_getconnector(struct drm_device *dev, void *data, out_resp->connector_type = connector->connector_type; out_resp->connector_type_id = connector->connector_type_id; + is_current_master = drm_is_current_master(file_priv); + mutex_lock(&dev->mode_config.mutex); if (out_resp->count_modes == 0) { - if (drm_is_current_master(file_priv)) + if (is_current_master) connector->funcs->fill_modes(connector, dev->mode_config.max_width, dev->mode_config.max_height);