From patchwork Wed Jun 19 00:17:03 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Pinchart X-Patchwork-Id: 13703242 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A7544380; Wed, 19 Jun 2024 00:17:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718756269; cv=none; b=D4cLmyxoVS1Uos2HNT6wTO9RqaPwr0kiU07fRZF+vQsquIERp5q44UOHIQzkDV6uLZ8UMS/UaS6qICBciGLwgPAhKgGfdyaAmKNZIT3SFdklpMJKcit6iOCHvyP4uGG9vDBEzesQbcT3qcyzmxUMqe44zuOj8NaopOxKD7t4Sns= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1718756269; c=relaxed/simple; bh=U0/yZ4650+9J09rA8FN4rUiL40HePqyho5dz5lfvEjA=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=StjG1B47JxsFV7kkwvTHPm7ubNfJ3qg8FZaWwO3b0+iH2DK9pMYU9cpw2LOvWWHclxCaFnkdY12Yw5+1WhbRA8SBdvg44kW9K4zWlIoQcVw6RFkUuLRZPvg7g06lDb+NrOlQYVADaqQEEqHkqPY9KPHxUeX48jjj7OQIzWk+VVo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=iyzTKzw5; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="iyzTKzw5" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 8B726E39; Wed, 19 Jun 2024 02:17:26 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1718756246; bh=U0/yZ4650+9J09rA8FN4rUiL40HePqyho5dz5lfvEjA=; h=From:To:Cc:Subject:Date:From; b=iyzTKzw5v9jmPcosKayY9dqi2lQJpBRBtqmuQoFOjpbSdGHTUkEgZDF/+HSp0rXne X0wYNNgJNPRf55JVTzFN1fxWVcAk0s+53J8NEcqldir4HGzgnEXFQZtY7Vr0p0IFOx a4V5hU6mQxQL+oW4KnQzjV7Ay7RG9DQatlm9ChnA= From: Laurent Pinchart To: linux-media@vger.kernel.org Cc: linux-renesas-soc@vger.kernel.org, Sakari Ailus , Tomi Valkeinen , Jacopo Mondi , Kieran Bingham Subject: [PATCH v2 00/19] media: renesas: vsp1: Conversion to subdev active state Date: Wed, 19 Jun 2024 03:17:03 +0300 Message-ID: <20240619001722.9749-1-laurent.pinchart+renesas@ideasonboard.com> X-Mailer: git-send-email 2.44.2 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Hello, This patch series is the second version of the vsp1 driver conversion to using the subdev active state. This version suffers from the same main lockdep issue as v1 (see below), but I decided to still repost it as the first 17 patches can go in already while we figure out how to handle the lockdep issue. The driver is fairly complex and creates many subdevs, exposing them to userspace through subdev nodes but also controlling them from within the kernel when acting as a backend for the R-Car DU display driver. It is thus a good testing ground to validate the subdev active state API. The first 17 patches are miscellaneous refactoring and cleanups to prepare for the actual conversion. In the middle of that is patch 11/19, which adds a function to dump a pipeline to the kernel log, which came very handy for debugging. Patch 18/19 is the actual conversion to the active state API. While I tried to keep it as small as possible by handling all the refactoring in separate patches, it's still the largest one in the series, mostly due to the fact that the drivers creates many subdevs. If that's any consolation, the diffstat is nice (net removal of 261 lines). Patch 19/19 is then an additional cleanup on top. The good news is that both the VSP test suite ([1]) and the display test suite ([2]) pass. The bad news is that lockdep complains quite heavily: [ 276.810170] ============================================ [ 276.815489] WARNING: possible recursive locking detected [ 276.820813] 6.10.0-rc3-00175-g639ee34a20f1 #803 Not tainted [ 276.826401] -------------------------------------------- [ 276.831724] yavta/1481 is trying to acquire lock: [ 276.836442] ffff00000ff26868 (vsp1_entity:531:sd->active_state->lock){+.+.}-{3:3}, at: v4l2_subdev_link_validate+0x140/0x308 [ 276.847736] [ 276.847736] but task is already holding lock: [ 276.853581] ffff00000ff27c68 (vsp1_entity:531:sd->active_state->lock){+.+.}-{3:3}, at: v4l2_subdev_link_validate+0x118/0x308 [ 276.864856] [ 276.864856] other info that might help us debug this: [ 276.871396] Possible unsafe locking scenario: [ 276.871396] [ 276.877326] CPU0 [ 276.879779] ---- [ 276.882232] lock(vsp1_entity:531:sd->active_state->lock); [ 276.887827] lock(vsp1_entity:531:sd->active_state->lock); [ 276.893422] [ 276.893422] *** DEADLOCK *** [ 276.893422] [ 276.899349] May be due to missing lock nesting notation [ 276.899349] [ 276.906145] 3 locks held by yavta/1481: [ 276.909996] #0: ffff00000fcaa7a0 (&video->lock){+.+.}-{3:3}, at: __video_do_ioctl+0x19c/0x5b0 [ 276.918666] #1: ffff00000fc9f418 (&mdev->graph_mutex){+.+.}-{3:3}, at: vsp1_video_streamon+0xec/0x4e8 [ 276.928031] #2: ffff00000ff27c68 (vsp1_entity:531:sd->active_state->lock){+.+.}-{3:3}, at: v4l2_subdev_link_validate+0x118/0x308 [ 276.939744] [ 276.939744] stack backtrace: [ 276.944114] CPU: 1 PID: 1481 Comm: yavta Not tainted 6.10.0-rc3-00175-g639ee34a20f1 #803 [ 276.952225] Hardware name: Renesas Salvator-X 2nd version board based on r8a77965 (DT) [ 276.960157] Call trace: [ 276.962616] dump_backtrace+0xa0/0x128 [ 276.966391] show_stack+0x20/0x38 [ 276.969723] dump_stack_lvl+0x8c/0xd0 [ 276.973412] dump_stack+0x1c/0x28 [ 276.976747] print_deadlock_bug+0x29c/0x3b0 [ 276.980950] __lock_acquire+0x165c/0x1b80 [ 276.984978] lock_acquire.part.0+0x168/0x310 [ 276.989265] lock_acquire+0x70/0x90 [ 276.992772] __mutex_lock+0x10c/0x4b8 [ 276.996458] mutex_lock_nested+0x2c/0x40 [ 277.000396] v4l2_subdev_link_validate+0x140/0x308 [ 277.005213] __media_pipeline_start+0x880/0xc30 [ 277.009763] __video_device_pipeline_start+0x48/0x68 [ 277.014750] vsp1_video_streamon+0x148/0x4e8 [ 277.019044] v4l_streamon+0x50/0x70 [ 277.022553] __video_do_ioctl+0x4cc/0x5b0 [ 277.026583] video_usercopy+0x3c4/0xb90 [ 277.030438] video_ioctl2+0x20/0x48 [ 277.033942] v4l2_ioctl+0xa4/0xc8 [ 277.037278] __arm64_sys_ioctl+0xec/0x118 [ 277.041310] invoke_syscall+0x68/0x198 [ 277.045084] el0_svc_common.constprop.0+0x80/0x150 [ 277.049900] do_el0_svc+0x38/0x50 [ 277.053237] el0_svc+0x4c/0xc0 [ 277.056309] el0t_64_sync_handler+0x120/0x130 [ 277.060685] el0t_64_sync+0x190/0x198 There is no actual deadlock situation caused by the tests, but a lockdep class deadlock detection. Subdev initialization is handled in one helper function for all subdevs created by the driver. This causes all locks for the active state being created with the same lock class. As a result, when validating links and trying to lock both the sink and source states, lockdep complains of recursive locking, even if the two locks are different mutex instances. Working around the issue is likely possible. The v4l2_subdev_init_finalize() function is actually a macro calling __v4l2_subdev_init_finalize() with an explicit lock class. The VSP1 driver could do the same and push the lock class one layer up, to the callers of vsp1_entity_init(). This would solve part of the problem only, as the driver creates multiple subdevs of the same type, so dynamic allocation of the lock class may be required. That would however be a bad solution, or rather not a solution to the actual problem. There is a reason why lockdep groups locks in classes, beside just saving memory. When locks belonging to different instances of the same object type are taken recursively, it is often the sign of a bad design. Even if we worked around this problem, lockdep would later complain about AB-BA locking at link validation time. The VSP1 entities can be assembled in a pipeline in any order, so even if the link validation helpers are careful to always lock in the sink-source order, the sink and source could get swapped. I believe this calls for a rework of locking for subdev states. The option I'm envisioning is to lock all subdevs in a pipeline when starting the pipeline, with a new media_pipeline_lock() call just before media_pipeline_start(). The link validation helpers would then be called with all locks taken, and so would the .s_stream() subdev operations. This would simplify locking in drivers as a result, which I think is a very desirable side effect. Then, after starting the pipeline, the top-level driver would call media_pipeline_unlock(). Similar locking would be performed at pipeline stop time, to ensure that the .s_stream() operations would also be called with the locks held. Obviously, just moving locking around won't fix the lockdep issues, and the second part of the fix would be to use ww-mutexes instead of regular mutexes. The result would be similar to the implementation of the KMS atomic API, giving me some confidence that it goes in the right direction. An additional difficulty, however, is that we need to lock both the subdev active state and the control handler with the same lock. Of course, I'm open to other proposals. [1] https://git.ideasonboard.com/renesas/vsp-tests.git [2] https://git.ideasonboard.com/renesas/kms-tests.git Laurent Pinchart (19): media: renesas: vsp1: Drop vsp1_entity_get_pad_format() wrapper media: renesas: vsp1: Drop vsp1_entity_get_pad_selection() wrapper media: renesas: vsp1: Drop vsp1_rwpf_get_crop() wrapper media: renesas: vsp1: Drop brx_get_compose() wrapper media: renesas: vsp1: Drop custom .get_fmt() handler for histogram media: renesas: vsp1: Move partition calculation to vsp1_pipe.c media: renesas: vsp1: Simplify partition calculation media: renesas: vsp1: Store RPF partition configuration per RPF instance media: renesas: vsp1: Pass partition pointer to .configure_partition() media: renesas: vsp1: Replace vsp1_partition_window with v4l2_rect media: renesas: vsp1: Add and use function to dump a pipeline to the log media: renesas: vsp1: Keep the DRM pipeline entities sorted media: renesas: vsp1: Compute partitions for DRM pipelines media: renesas: vsp1: Get configuration from partition instead of state media: renesas: vsp1: Name parameters to entity operations media: renesas: vsp1: Pass subdev state to entity operations media: renesas: vsp1: Initialize control handler after subdev media: renesas: vsp1: Switch to V4L2 subdev active state media: renesas: vsp1: Rename all v4l2_subdev_state variables to 'state' .../media/platform/renesas/vsp1/vsp1_brx.c | 84 ++------ .../media/platform/renesas/vsp1/vsp1_clu.c | 20 +- .../media/platform/renesas/vsp1/vsp1_drm.c | 48 ++++- .../media/platform/renesas/vsp1/vsp1_drm.h | 2 + .../media/platform/renesas/vsp1/vsp1_entity.c | 202 +++--------------- .../media/platform/renesas/vsp1/vsp1_entity.h | 66 +++--- .../media/platform/renesas/vsp1/vsp1_hgo.c | 30 +-- .../media/platform/renesas/vsp1/vsp1_hgt.c | 22 +- .../media/platform/renesas/vsp1/vsp1_histo.c | 116 +++------- .../media/platform/renesas/vsp1/vsp1_hsit.c | 32 +-- .../media/platform/renesas/vsp1/vsp1_lif.c | 18 +- .../media/platform/renesas/vsp1/vsp1_lut.c | 17 +- .../media/platform/renesas/vsp1/vsp1_pipe.c | 111 +++++++++- .../media/platform/renesas/vsp1/vsp1_pipe.h | 48 +++-- .../media/platform/renesas/vsp1/vsp1_rpf.c | 60 +++--- .../media/platform/renesas/vsp1/vsp1_rwpf.c | 89 ++------ .../media/platform/renesas/vsp1/vsp1_rwpf.h | 3 - .../media/platform/renesas/vsp1/vsp1_sru.c | 84 +++----- .../media/platform/renesas/vsp1/vsp1_uds.c | 96 +++------ .../media/platform/renesas/vsp1/vsp1_uif.c | 66 ++---- .../media/platform/renesas/vsp1/vsp1_video.c | 193 ++++++----------- .../media/platform/renesas/vsp1/vsp1_wpf.c | 46 ++-- 22 files changed, 559 insertions(+), 894 deletions(-) base-commit: 91798162245991e26949ef62851719bb2177a9c2