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GET /api/patches/2215387/?format=api
{ "id": 2215387, "url": "http://patchwork.ozlabs.org/api/patches/2215387/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-tegra/patch/20260324-drm-bridge-atomic-vs-remove-private_obj-v3-1-64deefe84044@bootlin.com/", "project": { "id": 21, "url": "http://patchwork.ozlabs.org/api/projects/21/?format=api", "name": "Linux Tegra Development", "link_name": "linux-tegra", "list_id": "linux-tegra.vger.kernel.org", "list_email": "linux-tegra@vger.kernel.org", "web_url": null, "scm_url": null, "webscm_url": null, "list_archive_url": "", "list_archive_url_format": "", "commit_url_format": "" }, "msgid": "<20260324-drm-bridge-atomic-vs-remove-private_obj-v3-1-64deefe84044@bootlin.com>", "list_archive_url": null, "date": "2026-03-24T13:07:30", "name": "[v3] drm/atomic: drm_atomic_private_obj_fini: protect private_obj removal from list", "commit_ref": null, "pull_url": null, "state": "new", "archived": false, "hash": "6c5436de95d463405a22b14047c3cd56c855cdb3", "submitter": { "id": 83908, "url": "http://patchwork.ozlabs.org/api/people/83908/?format=api", "name": "Luca Ceresoli", "email": "luca.ceresoli@bootlin.com" }, "delegate": null, "mbox": "http://patchwork.ozlabs.org/project/linux-tegra/patch/20260324-drm-bridge-atomic-vs-remove-private_obj-v3-1-64deefe84044@bootlin.com/mbox/", "series": [ { "id": 497287, "url": "http://patchwork.ozlabs.org/api/series/497287/?format=api", "web_url": "http://patchwork.ozlabs.org/project/linux-tegra/list/?series=497287", "date": "2026-03-24T13:07:30", "name": "[v3] drm/atomic: drm_atomic_private_obj_fini: protect private_obj removal from list", "version": 3, "mbox": "http://patchwork.ozlabs.org/series/497287/mbox/" } ], "comments": "http://patchwork.ozlabs.org/api/patches/2215387/comments/", "check": "pending", "checks": "http://patchwork.ozlabs.org/api/patches/2215387/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "\n <linux-tegra+bounces-13117-incoming=patchwork.ozlabs.org@vger.kernel.org>", "X-Original-To": [ "incoming@patchwork.ozlabs.org", "linux-tegra@vger.kernel.org" ], "Delivered-To": "patchwork-incoming@legolas.ozlabs.org", "Authentication-Results": [ "legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=bootlin.com header.i=@bootlin.com header.a=rsa-sha256\n header.s=dkim header.b=QcbodRRZ;\n\tdkim-atps=neutral", "legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=104.64.211.4; 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a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116;\n\tt=1774357676; cv=none;\n b=ikL3FvCbx9/u820CApNroKI4gKEf6EAO3IYZ46OTnABbyaioHjSDEFZ5xIdDugEABujkgl0bLVy7Y0ImD/X2pUxcVhhi5qfJqu2mROrkKLQg2X/ifqmEexXSBymzt+/CeiLpKjJEf9tiXaFmxOd4YbKHhvN2Ys3OpCU+6EcN4GM=", "ARC-Message-Signature": "i=1; a=rsa-sha256; d=subspace.kernel.org;\n\ts=arc-20240116; t=1774357676; c=relaxed/simple;\n\tbh=3gcDvKDiofu5+UBNldcs7iRDdzjLiu7N536dnvCCZcA=;\n\th=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References:\n\t In-Reply-To:To:Cc;\n b=tKs7ytyoAQ+yUhqVmz/qiNTxGUEDD2Iac7V2BMZuBH+sCEQwQh+j0opvzanKC89JnHUE3+UnNm4kcU/6R2hti85QYDel3SRIDbWNmwfddddwES3dDzc8ap1stC+5z5z8xd4QsstzVHikIc/1eO6G/upY9gAmzFGtsZGDym5eM34=", "ARC-Authentication-Results": "i=1; smtp.subspace.kernel.org;\n dmarc=pass (p=reject dis=none) header.from=bootlin.com;\n spf=pass smtp.mailfrom=bootlin.com;\n dkim=pass (2048-bit key) header.d=bootlin.com header.i=@bootlin.com\n header.b=QcbodRRZ; arc=none smtp.client-ip=185.246.84.56", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed; d=bootlin.com; s=dkim;\n\tt=1774357670; h=from:subject:date:message-id:to:cc:mime-version:content-type:\n\t content-transfer-encoding:in-reply-to:references;\n\tbh=fzs1pWNycSsS39sE+twHeUSR+qT4+7glSHwX8hsiv/I=;\n\tb=QcbodRRZQ7IqeUKtkAQoCsXRCzX49zCQ7c/T+hCSVAXapnmgLoW9sIiyhNT46+mtFpU61J\n\tgJKeSKsjZKwJOSysmrVxJF3olbTeDJZ2DqVTCNwCP9TRBajYIcDIENx5tLs+7THxp2dWu0\n\tG/nuEQt7uiBb0r0BIkhRCZVn6pXSbqYfjcLzD/L4CbpSNR9WLcFeTQpZ4rS6QK/GzA8nkX\n\th9C6LEGO1+qyCWSTqAgOYNv4hY+3xqTMYTAflOF0bmF5eF20QckGAirTPjA+Op1MqF0Nv7\n\t40zg4pJn5YPXFwI/uVYiiJu5XpAy2TfiMXAYQmP7sGyJ6NVFPthK0xMFXjZ6wA==", "From": "Luca Ceresoli <luca.ceresoli@bootlin.com>", "Date": "Tue, 24 Mar 2026 14:07:30 +0100", "Subject": "[PATCH v3] drm/atomic: drm_atomic_private_obj_fini: protect\n private_obj removal from list", "Precedence": "bulk", "X-Mailing-List": "linux-tegra@vger.kernel.org", "List-Id": "<linux-tegra.vger.kernel.org>", "List-Subscribe": "<mailto:linux-tegra+subscribe@vger.kernel.org>", "List-Unsubscribe": "<mailto:linux-tegra+unsubscribe@vger.kernel.org>", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=\"utf-8\"", "Content-Transfer-Encoding": "7bit", "Message-Id": "\n <20260324-drm-bridge-atomic-vs-remove-private_obj-v3-1-64deefe84044@bootlin.com>", "References": "\n <20260324-drm-bridge-atomic-vs-remove-private_obj-v3-0-64deefe84044@bootlin.com>", "In-Reply-To": "\n <20260324-drm-bridge-atomic-vs-remove-private_obj-v3-0-64deefe84044@bootlin.com>", "To": "Harry Wentland <harry.wentland@amd.com>, Leo Li <sunpeng.li@amd.com>,\n Rodrigo Siqueira <siqueira@igalia.com>,\n Alex Deucher <alexander.deucher@amd.com>,\n =?utf-8?q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,\n David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,\n Liviu Dudau <liviu.dudau@arm.com>,\n Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,\n Maxime Ripard <mripard@kernel.org>, Thomas Zimmermann <tzimmermann@suse.de>,\n Andrzej Hajda <andrzej.hajda@intel.com>,\n Neil Armstrong <neil.armstrong@linaro.org>, Robert Foss <rfoss@kernel.org>,\n Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,\n Jonas Karlman <jonas@kwiboo.se>, Jernej Skrabec <jernej.skrabec@gmail.com>,\n Paul Cercueil <paul@crapouillou.net>,\n Rob Clark <robin.clark@oss.qualcomm.com>,\n Dmitry Baryshkov <lumag@kernel.org>,\n Abhinav Kumar <abhinav.kumar@linux.dev>, Sean Paul <sean@poorly.run>,\n Marijn Suijten <marijn.suijten@somainline.org>,\n Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>,\n Thierry Reding <thierry.reding@gmail.com>,\n Mikko Perttunen <mperttunen@nvidia.com>,\n Jonathan Hunter <jonathanh@nvidia.com>,\n Dave Stevenson <dave.stevenson@raspberrypi.com>, =?utf-8?q?Ma=C3=ADra_Cana?=\n\t=?utf-8?q?l?= <mcanal@igalia.com>,\n Raspberry Pi Kernel Maintenance <kernel-list@raspberrypi.com>", "Cc": "Hui Pu <Hui.Pu@gehealthcare.com>,\n Thomas Petazzoni <thomas.petazzoni@bootlin.com>,\n amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,\n linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,\n linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org,\n linux-tegra@vger.kernel.org, Ian Ray <ian.ray@gehealthcare.com>,\n Luca Ceresoli <luca.ceresoli@bootlin.com>", "X-Mailer": "b4 0.15.0", "X-Last-TLS-Session-Version": "TLSv1.3" }, "content": "Currently drm_bridge_detach() expects that the bridge private_obj is not\nlocked by a drm_modeset_acquire_ctx, and it warns in case that happens:\n\n drm_bridge_detach()\n -> drm_atomic_private_obj_fini()\n -> list_del(&obj->head) // removes priv_obj from\n // dev->mode_config.privobj_list\n -> obj->funcs->atomic_destroy_state()\n -> drm_modeset_lock_fini(&obj->lock)\n -> WARN_ON(!list_empty(&lock->head)) // warn if priv_obj->lock\n\t // is still in ctx->locked\n\nThe expectation is not respected when introducing bridge hot-plugging. In\nsuch case the warning triggers if the bridge is being removed concurrently\nto an operation that locks the private object using a\ndrm_modeset_acquire_ctx, such as in this execution scenario:\n\n CPU0:\n drm_mode_obj_get_properties_ioctl() // userspace request\n -> DRM_MODESET_LOCK_ALL_BEGIN()\n . -> drm_for_each_privobj() // loop on dev->mode_config.privobj_list\n . - lock the privobj mutex\n .\t- add priv_obj->lock to ctx->locked\n .\t (list of locks to be released later)\n .\n . CPU1:\n . drm_bridge_detach() // bridge hot-unplug\n .\t\t -> WARN triggers!\n .\n -> DRM_MODESET_LOCK_ALL_END()\n -> for each lock in ctx->locked\n\t- remove priv_obj->lock from ctx->locked\n - unlock the privobj mutex\n\nPrevent this potential deadlock by using DRM_MODESET_LOCK_ALL_BEGIN/END()\naround the list removal in drm_atomic_private_obj_fini(). This ensures that\nexactly one of these happens:\n\n * the concurrent code (e.g. drm_mode_obj_get_properties_ioctl()) acquires\n all the locks first, so it can execute fully and release the\n privobj->lock before drm_atomic_private_obj_fini() calls list_del() and\n before the WARN_ON()\n * drm_atomic_private_obj_fini() acquires all the locks first, so it\n removes its privobj->lock from the dev->mode_config.privobj_list; the\n concurrent code will run afterwards and not acquire that lock because it\n is not present anymore\n\nSigned-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>\n\n---\n\nChanges in v3:\n- Rebased on current drm-misc-next (on 7.0-rc3)\n- Small commit message clarification\n\nChanges in v2:\n- added 'drm/atomic:' prefix to commit title\n- Adapted to work on top of \"drm/atomic: Add dev pointer to drm_private_obj\"\n- Slightly improved commit message\n---\n drivers/gpu/drm/drm_atomic.c | 6 ++++++\n 1 file changed, 6 insertions(+)", "diff": "diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c\nindex 41c57063f3b4..0f9c2528c9ee 100644\n--- a/drivers/gpu/drm/drm_atomic.c\n+++ b/drivers/gpu/drm/drm_atomic.c\n@@ -962,7 +962,13 @@ EXPORT_SYMBOL(drm_atomic_private_obj_init);\n void\n drm_atomic_private_obj_fini(struct drm_private_obj *obj)\n {\n+\tstruct drm_modeset_acquire_ctx ctx;\n+\tint ret = 0;\n+\n+\tDRM_MODESET_LOCK_ALL_BEGIN(obj->dev, ctx, 0, ret);\n \tlist_del(&obj->head);\n+\tDRM_MODESET_LOCK_ALL_END(obj->dev, ctx, ret);\n+\n \tobj->funcs->atomic_destroy_state(obj, obj->state);\n \tdrm_modeset_lock_fini(&obj->lock);\n }\n", "prefixes": [ "v3" ] }