{"id":23000,"url":"https://patchwork.libcamera.org/api/1.1/patches/23000/?format=json","web_url":"https://patchwork.libcamera.org/patch/23000/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/1.1/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20250324115123.155044-1-barnabas.pocze@ideasonboard.com>","date":"2025-03-24T11:51:23","name":"[v2] libcamera: camera_manager: Do not emit signals while holding lock","commit_ref":null,"pull_url":null,"state":"accepted","archived":false,"hash":"157b20e39e77bd5f568c811e16161bcdcdace011","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/1.1/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/23000/mbox/","series":[{"id":5076,"url":"https://patchwork.libcamera.org/api/1.1/series/5076/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5076","date":"2025-03-24T11:51:23","name":"[v2] libcamera: camera_manager: Do not emit signals while holding lock","version":2,"mbox":"https://patchwork.libcamera.org/series/5076/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/23000/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/23000/checks/","tags":{},"headers":{"Return-Path":"","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 D6F2BC3213\n\tfor ;\n\tMon, 24 Mar 2025 11:51:29 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id CE50668953;\n\tMon, 24 Mar 2025 12:51:28 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 75D4B68945\n\tfor ;\n\tMon, 24 Mar 2025 12:51:27 +0100 (CET)","from pb-laptop.local (185.221.143.221.nat.pool.zt.hu\n\t[185.221.143.221])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id A87E0455;\n\tMon, 24 Mar 2025 12:49:40 +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=\"tuC7x+WH\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1742816981;\n\tbh=MgJ4i/VeqEmupm+Nd1YWjUjT4FeBuB1P07GnD64N608=;\n\th=From:To:Cc:Subject:Date:From;\n\tb=tuC7x+WHs5omLzgdDv6uZ7kHvIFES5lwYal1Sh6Bhx5UNvuG3wwvBn7K5fkbUNlhb\n\tiKob5CHRHn5ty1nd7Nnsnvgr9Uoy1XPVIY4YqP2iAT+dhJRnXgVT0czLYOokuidDmN\n\tgV/JiDQWuBeLbPg/PtlpEE/kIRRIkYSUJylK5X4Y=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org","Cc":"Harvey Yang ,\n\tLaurent Pinchart ","Subject":"[PATCH v2] libcamera: camera_manager: Do not emit signals while\n\tholding lock","Date":"Mon, 24 Mar 2025 12:51:23 +0100","Message-ID":"<20250324115123.155044-1-barnabas.pocze@ideasonboard.com>","X-Mailer":"git-send-email 2.49.0","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":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"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 \nReviewed-by: Harvey Yang \nReviewed-by: Laurent Pinchart \n---\nchanges in v2:\n * indent scopes properly\n * drop `std::move()` calls\n\n\nv1: https://patchwork.libcamera.org/patch/22905/\n---\n src/libcamera/camera_manager.cpp | 44 +++++++++++++++++---------------\n 1 file changed, 23 insertions(+), 21 deletions(-)\n\n--\n2.49.0","diff":"diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp\nindex 87e6717ec..400109f12 100644\n--- a/src/libcamera/camera_manager.cpp\n+++ b/src/libcamera/camera_manager.cpp\n@@ -202,24 +202,24 @@ void CameraManager::Private::addCamera(std::shared_ptr camera)\n {\n \tASSERT(Thread::current() == this);\n\n-\tMutexLocker locker(mutex_);\n+\t{\n+\t\tMutexLocker locker(mutex_);\n\n-\tfor (const std::shared_ptr &c : cameras_) {\n-\t\tif (c->id() == camera->id()) {\n-\t\t\tLOG(Camera, Fatal)\n-\t\t\t\t<< \"Trying to register a camera with a duplicated ID '\"\n-\t\t\t\t<< camera->id() << \"'\";\n-\t\t\treturn;\n+\t\tfor (const std::shared_ptr &c : cameras_) {\n+\t\t\tif (c->id() == camera->id()) {\n+\t\t\t\tLOG(Camera, Fatal)\n+\t\t\t\t\t<< \"Trying to register a camera with a duplicated ID '\"\n+\t\t\t\t\t<< camera->id() << \"'\";\n+\t\t\t\treturn;\n+\t\t\t}\n \t\t}\n-\t}\n\n-\tcameras_.push_back(std::move(camera));\n-\n-\tunsigned int index = cameras_.size() - 1;\n+\t\tcameras_.push_back(camera);\n+\t}\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(camera);\n }\n\n /**\n@@ -236,20 +236,22 @@ void CameraManager::Private::removeCamera(std::shared_ptr camera)\n {\n \tASSERT(Thread::current() == this);\n\n-\tMutexLocker locker(mutex_);\n+\t{\n+\t\tMutexLocker locker(mutex_);\n\n-\tauto iter = std::find_if(cameras_.begin(), cameras_.end(),\n-\t\t\t\t [camera](std::shared_ptr &c) {\n-\t\t\t\t\t return c.get() == camera.get();\n-\t\t\t\t });\n-\tif (iter == cameras_.end())\n-\t\treturn;\n+\t\tauto iter = std::find_if(cameras_.begin(), cameras_.end(),\n+\t\t\t\t\t [camera](std::shared_ptr &c) {\n+\t\t\t\t\t\t return c.get() == camera.get();\n+\t\t\t\t\t });\n+\t\tif (iter == cameras_.end())\n+\t\t\treturn;\n+\n+\t\tcameras_.erase(iter);\n+\t}\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","prefixes":["v2"]}