[{"id":33690,"web_url":"https://patchwork.libcamera.org/comment/33690/","msgid":"<174282218424.3289779.5514946600756888518@ping.linuxembedded.co.uk>","date":"2025-03-24T13:16:24","subject":"Re: [PATCH v2] libcamera: camera_manager: Do not emit signals while\n\tholding lock","submitter":{"id":4,"url":"https://patchwork.libcamera.org/api/people/4/","name":"Kieran Bingham","email":"kieran.bingham@ideasonboard.com"},"content":"Quoting Barnabás Pőcze (2025-03-24 11:51:23)\n> Both `CameraManager::Private::{add,remove}Camera()` emit the\n> `camera{Added,Removed}` signals, respectively, while holding the\n> lock protecting the list of cameras.\n> \n> This is problematic because if a callback tries to call `cameras()`,\n> then the same (non-recursive) lock would be locked again.\n> \n> Furthermore, there is no real need to hold the lock while user code\n> is running, so release the lock as soon as possible.\n> \n> Signed-off-by: Barnabás Pőcze \n> Reviewed-by: Harvey Yang \n> Reviewed-by: Laurent Pinchart \n> ---\n> changes in v2:\n> * indent scopes properly\n> * drop `std::move()` calls\n> \n> \n> v1: https://patchwork.libcamera.org/patch/22905/\n> ---\n> src/libcamera/camera_manager.cpp | 44 +++++++++++++++++---------------\n> 1 file changed, 23 insertions(+), 21 deletions(-)\n> \n> diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp\n> index 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> ASSERT(Thread::current() == this);\n> \n> - MutexLocker locker(mutex_);\n> + {\n> + MutexLocker locker(mutex_);\n\nThanks, the indents make patches harder to parse, but the code clearer\nto read :-)\n\n\n\nReviewed-by: Kieran Bingham \n\n\n\n> \n> - for (const std::shared_ptr &c : cameras_) {\n> - if (c->id() == camera->id()) {\n> - LOG(Camera, Fatal)\n> - << \"Trying to register a camera with a duplicated ID '\"\n> - << camera->id() << \"'\";\n> - return;\n> + for (const std::shared_ptr &c : cameras_) {\n> + if (c->id() == camera->id()) {\n> + LOG(Camera, Fatal)\n> + << \"Trying to register a camera with a duplicated ID '\"\n> + << camera->id() << \"'\";\n> + return;\n> + }\n> }\n> - }\n> \n> - cameras_.push_back(std::move(camera));\n> -\n> - unsigned int index = cameras_.size() - 1;\n> + cameras_.push_back(camera);\n> + }\n> \n> /* Report the addition to the public signal */\n> CameraManager *const o = LIBCAMERA_O_PTR();\n> - o->cameraAdded.emit(cameras_[index]);\n> + o->cameraAdded.emit(camera);\n> }\n> \n> /**\n> @@ -236,20 +236,22 @@ void CameraManager::Private::removeCamera(std::shared_ptr camera)\n> {\n> ASSERT(Thread::current() == this);\n> \n> - MutexLocker locker(mutex_);\n> + {\n> + MutexLocker locker(mutex_);\n> \n> - auto iter = std::find_if(cameras_.begin(), cameras_.end(),\n> - [camera](std::shared_ptr &c) {\n> - return c.get() == camera.get();\n> - });\n> - if (iter == cameras_.end())\n> - return;\n> + auto iter = std::find_if(cameras_.begin(), cameras_.end(),\n> + [camera](std::shared_ptr &c) {\n> + return c.get() == camera.get();\n> + });\n> + if (iter == cameras_.end())\n> + return;\n> +\n> + cameras_.erase(iter);\n> + }\n> \n> LOG(Camera, Debug)\n> << \"Unregistering camera '\" << camera->id() << \"'\";\n> \n> - cameras_.erase(iter);\n> -\n> /* Report the removal to the public signal */\n> CameraManager *const o = LIBCAMERA_O_PTR();\n> o->cameraRemoved.emit(camera);\n> --\n> 2.49.0","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 4D5DCC0DA4\n\tfor ;\n\tMon, 24 Mar 2025 13:16:30 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 3FCE768951;\n\tMon, 24 Mar 2025 14:16:29 +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 E5A4B6893F\n\tfor ;\n\tMon, 24 Mar 2025 14:16:27 +0100 (CET)","from pendragon.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 337FE455;\n\tMon, 24 Mar 2025 14:14:41 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; 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