From patchwork Mon Mar 24 11:51:23 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= X-Patchwork-Id: 23000 Return-Path: X-Original-To: parsemail@patchwork.libcamera.org Delivered-To: parsemail@patchwork.libcamera.org Received: from lancelot.ideasonboard.com (lancelot.ideasonboard.com [92.243.16.209]) by patchwork.libcamera.org (Postfix) with ESMTPS id D6F2BC3213 for ; Mon, 24 Mar 2025 11:51:29 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id CE50668953; Mon, 24 Mar 2025 12:51:28 +0100 (CET) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="tuC7x+WH"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 75D4B68945 for ; Mon, 24 Mar 2025 12:51:27 +0100 (CET) Received: from pb-laptop.local (185.221.143.221.nat.pool.zt.hu [185.221.143.221]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id A87E0455; Mon, 24 Mar 2025 12:49:40 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1742816981; bh=MgJ4i/VeqEmupm+Nd1YWjUjT4FeBuB1P07GnD64N608=; h=From:To:Cc:Subject:Date:From; b=tuC7x+WHs5omLzgdDv6uZ7kHvIFES5lwYal1Sh6Bhx5UNvuG3wwvBn7K5fkbUNlhb iKob5CHRHn5ty1nd7Nnsnvgr9Uoy1XPVIY4YqP2iAT+dhJRnXgVT0czLYOokuidDmN gV/JiDQWuBeLbPg/PtlpEE/kIRRIkYSUJylK5X4Y= From: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= To: libcamera-devel@lists.libcamera.org Cc: Harvey Yang , Laurent Pinchart Subject: [PATCH v2] libcamera: camera_manager: Do not emit signals while holding 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 X-BeenThere: libcamera-devel@lists.libcamera.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: libcamera-devel-bounces@lists.libcamera.org Sender: "libcamera-devel" Both `CameraManager::Private::{add,remove}Camera()` emit the `camera{Added,Removed}` signals, respectively, while holding the lock protecting the list of cameras. This is problematic because if a callback tries to call `cameras()`, then the same (non-recursive) lock would be locked again. Furthermore, there is no real need to hold the lock while user code is running, so release the lock as soon as possible. Signed-off-by: Barnabás Pőcze Reviewed-by: Harvey Yang Reviewed-by: Laurent Pinchart Reviewed-by: Kieran Bingham --- changes in v2: * indent scopes properly * drop `std::move()` calls v1: https://patchwork.libcamera.org/patch/22905/ --- src/libcamera/camera_manager.cpp | 44 +++++++++++++++++--------------- 1 file changed, 23 insertions(+), 21 deletions(-) -- 2.49.0 diff --git a/src/libcamera/camera_manager.cpp b/src/libcamera/camera_manager.cpp index 87e6717ec..400109f12 100644 --- a/src/libcamera/camera_manager.cpp +++ b/src/libcamera/camera_manager.cpp @@ -202,24 +202,24 @@ void CameraManager::Private::addCamera(std::shared_ptr camera) { ASSERT(Thread::current() == this); - MutexLocker locker(mutex_); + { + MutexLocker locker(mutex_); - for (const std::shared_ptr &c : cameras_) { - if (c->id() == camera->id()) { - LOG(Camera, Fatal) - << "Trying to register a camera with a duplicated ID '" - << camera->id() << "'"; - return; + for (const std::shared_ptr &c : cameras_) { + if (c->id() == camera->id()) { + LOG(Camera, Fatal) + << "Trying to register a camera with a duplicated ID '" + << camera->id() << "'"; + return; + } } - } - cameras_.push_back(std::move(camera)); - - unsigned int index = cameras_.size() - 1; + cameras_.push_back(camera); + } /* Report the addition to the public signal */ CameraManager *const o = LIBCAMERA_O_PTR(); - o->cameraAdded.emit(cameras_[index]); + o->cameraAdded.emit(camera); } /** @@ -236,20 +236,22 @@ void CameraManager::Private::removeCamera(std::shared_ptr camera) { ASSERT(Thread::current() == this); - MutexLocker locker(mutex_); + { + MutexLocker locker(mutex_); - auto iter = std::find_if(cameras_.begin(), cameras_.end(), - [camera](std::shared_ptr &c) { - return c.get() == camera.get(); - }); - if (iter == cameras_.end()) - return; + auto iter = std::find_if(cameras_.begin(), cameras_.end(), + [camera](std::shared_ptr &c) { + return c.get() == camera.get(); + }); + if (iter == cameras_.end()) + return; + + cameras_.erase(iter); + } LOG(Camera, Debug) << "Unregistering camera '" << camera->id() << "'"; - cameras_.erase(iter); - /* Report the removal to the public signal */ CameraManager *const o = LIBCAMERA_O_PTR(); o->cameraRemoved.emit(camera);