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{ "id": 22905, "url": "https://patchwork.libcamera.org/api/patches/22905/?format=api", "web_url": "https://patchwork.libcamera.org/patch/22905/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20250303142010.714280-1-barnabas.pocze@ideasonboard.com>", "date": "2025-03-03T14:20:10", "name": "[v1] libcamera: camera_manager: Do not emit signals while holding lock", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": false, "hash": "feef204119ffdedb2eb3bfe209ff7b51af6633ce", "submitter": { "id": 216, "url": "https://patchwork.libcamera.org/api/people/216/?format=api", "name": "Barnabás Pőcze", "email": "barnabas.pocze@ideasonboard.com" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/22905/mbox/", "series": [ { "id": 5033, "url": "https://patchwork.libcamera.org/api/series/5033/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=5033", "date": "2025-03-03T14:20:10", "name": "[v1] libcamera: camera_manager: Do not emit signals while holding lock", "version": 1, "mbox": "https://patchwork.libcamera.org/series/5033/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/22905/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/22905/checks/", "tags": {}, "headers": { "Return-Path": "<libcamera-devel-bounces@lists.libcamera.org>", "X-Original-To": "parsemail@patchwork.libcamera.org", "Delivered-To": "parsemail@patchwork.libcamera.org", "Received": [ "from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 3B336BD808\n\tfor <parsemail@patchwork.libcamera.org>;\n\tMon, 3 Mar 2025 14:20:18 +0000 (UTC)", "from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 2549A687EB;\n\tMon, 3 Mar 2025 15:20:17 +0100 (CET)", "from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 0064268772\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tMon, 3 Mar 2025 15:20:14 +0100 (CET)", "from pb-laptop.local (185.221.143.4.nat.pool.zt.hu [185.221.143.4])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 79264346\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tMon, 3 Mar 2025 15:18:43 +0100 (CET)" ], "Authentication-Results": "lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"ACTlZ9Z8\"; dkim-atps=neutral", "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1741011523;\n\tbh=c4r/pJEhhSyInFGPBj6pSe19gl3oxdCK4R9br25tVOg=;\n\th=From:To:Subject:Date:From;\n\tb=ACTlZ9Z8/b88q0vhkEhPqI9bJvduYKu5mD7Fl4ins99F+uIsQJxPOQmwYN05NmdaJ\n\t48k1ftdX25z83333cQ9dDOd1vfaqACIvno81GPUjvKHPus1f2S8B5E6VLyYqF07TUx\n\tS/49ywDZQdJ4qo52XT2ry286VS8dqf6l6RSWFFew=", "From": "=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= <barnabas.pocze@ideasonboard.com>", "To": "libcamera-devel@lists.libcamera.org", "Subject": "[PATCH v1] libcamera: camera_manager: Do not emit signals while\n\tholding lock", "Date": "Mon, 3 Mar 2025 15:20:10 +0100", "Message-ID": "<20250303142010.714280-1-barnabas.pocze@ideasonboard.com>", "X-Mailer": "git-send-email 2.48.1", "MIME-Version": "1.0", "Content-Type": "text/plain; charset=UTF-8", "Content-Transfer-Encoding": "8bit", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "Errors-To": "libcamera-devel-bounces@lists.libcamera.org", "Sender": "\"libcamera-devel\" <libcamera-devel-bounces@lists.libcamera.org>" }, "content": "Both `CameraManager::Private::{add,remove}Camera()` emit the\n`camera{Added,Removed}` signals, respectively, while holding the\nlock protecting the list of cameras.\n\nThis is problematic because if a callback tries to call `cameras()`,\nthen the same (non-recursive) lock would be locked again.\n\nFurthermore, there is no real need to hold the lock while user code\nis running, so release the lock as soon as possible.\n\nSigned-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>\n---\n src/libcamera/camera_manager.cpp | 16 +++++++++-------\n 1 file changed, 9 insertions(+), 7 deletions(-)", "diff": "diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp\nindex 87e6717ec..d728ac44a 100644\n--- a/src/libcamera/camera_manager.cpp\n+++ b/src/libcamera/camera_manager.cpp\n@@ -202,6 +202,7 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> camera)\n {\n \tASSERT(Thread::current() == this);\n \n+{\n \tMutexLocker locker(mutex_);\n \n \tfor (const std::shared_ptr<Camera> &c : cameras_) {\n@@ -213,13 +214,12 @@ void CameraManager::Private::addCamera(std::shared_ptr<Camera> camera)\n \t\t}\n \t}\n \n-\tcameras_.push_back(std::move(camera));\n-\n-\tunsigned int index = cameras_.size() - 1;\n+\tcameras_.push_back(camera);\n+}\n \n \t/* Report the addition to the public signal */\n \tCameraManager *const o = LIBCAMERA_O_PTR();\n-\to->cameraAdded.emit(cameras_[index]);\n+\to->cameraAdded.emit(std::move(camera));\n }\n \n /**\n@@ -236,6 +236,7 @@ void CameraManager::Private::removeCamera(std::shared_ptr<Camera> camera)\n {\n \tASSERT(Thread::current() == this);\n \n+{\n \tMutexLocker locker(mutex_);\n \n \tauto iter = std::find_if(cameras_.begin(), cameras_.end(),\n@@ -245,14 +246,15 @@ void CameraManager::Private::removeCamera(std::shared_ptr<Camera> camera)\n \tif (iter == cameras_.end())\n \t\treturn;\n \n+\tcameras_.erase(iter);\n+}\n+\n \tLOG(Camera, Debug)\n \t\t<< \"Unregistering camera '\" << camera->id() << \"'\";\n \n-\tcameras_.erase(iter);\n-\n \t/* Report the removal to the public signal */\n \tCameraManager *const o = LIBCAMERA_O_PTR();\n-\to->cameraRemoved.emit(camera);\n+\to->cameraRemoved.emit(std::move(camera));\n }\n \n /**\n", "prefixes": [ "v1" ] }