[{"id":21396,"web_url":"https://patchwork.libcamera.org/comment/21396/","msgid":"","date":"2021-11-30T04:17:59","subject":"Re: [libcamera-devel] [PATCH v2 05/11] libcamera: base: Add mutex\n\tclasses with thread safety annotations","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Hiro,\n\nThank you for the patch.\n\nOn Mon, Nov 29, 2021 at 08:44:47PM +0900, Hirokazu Honda wrote:\n> This replaces Mutex and MutexLocker with our own defined classes.\n> The classes are annotated by clang thread safety annotations.\n> So we can add annotation to code where the classes are used.\n> \n> v4l2 code needs to be annotated, which violates Mutex capability.\n> \n> Signed-off-by: Hirokazu Honda \n> ---\n> include/libcamera/base/meson.build | 1 +\n> include/libcamera/base/mutex.h | 127 +++++++++++++++++++++++++++++\n> include/libcamera/base/thread.h | 7 +-\n> src/v4l2/v4l2_camera_proxy.h | 5 +-\n> 4 files changed, 132 insertions(+), 8 deletions(-)\n> create mode 100644 include/libcamera/base/mutex.h\n> \n> diff --git a/include/libcamera/base/meson.build b/include/libcamera/base/meson.build\n> index 1a71ce5a..37c4435a 100644\n> --- a/include/libcamera/base/meson.build\n> +++ b/include/libcamera/base/meson.build\n> @@ -13,6 +13,7 @@ libcamera_base_headers = files([\n> 'flags.h',\n> 'log.h',\n> 'message.h',\n> + 'mutex.h',\n> 'object.h',\n> 'private.h',\n> 'semaphore.h',\n> diff --git a/include/libcamera/base/mutex.h b/include/libcamera/base/mutex.h\n> new file mode 100644\n> index 00000000..55091eb4\n> --- /dev/null\n> +++ b/include/libcamera/base/mutex.h\n> @@ -0,0 +1,127 @@\n> +/* SPDX-License-Identifier: LGPL-2.1-or-later */\n> +/*\n> + * Copyright (C) 2021, Google Inc.\n> + *\n> + * thread.h - Thread support\n> + */\n> +\n> +#pragma once\n> +\n> +#include \n> +#include \n> +\n> +#include \n> +\n> +namespace libcamera {\n> +\n> +class ConditionVariable;\n> +class LIBCAMERA_TSA_SCOPED_CAPABILITY MutexLocker;\n> +\n> +/* \\todo using Mutex = std::mutex if lib++ is used. */\n> +class LIBCAMERA_TSA_CAPABILITY(\"mutex\") Mutex final\n> +{\n> +public:\n> +\tconstexpr Mutex()\n> +\t{\n> +\t}\n> +\n> +\tvoid lock() LIBCAMERA_TSA_ACQUIRE()\n> +\t{\n> +\t\tmutex_.lock();\n> +\t}\n> +\n> +\tvoid unlock() LIBCAMERA_TSA_RELEASE()\n> +\t{\n> +\t\tmutex_.unlock();\n> +\t}\n> +\n> +private:\n> +\tfriend MutexLocker;\n> +\n> +\tstd::mutex mutex_;\n> +};\n> +\n> +class LIBCAMERA_TSA_SCOPED_CAPABILITY MutexLocker final\n> +{\n> +public:\n> +\texplicit MutexLocker(Mutex &mutex) LIBCAMERA_TSA_ACQUIRE(mutex)\n> +\t\t: lock_(mutex.mutex_)\n> +\t{\n> +\t}\n> +\n> +\tMutexLocker(Mutex &mutex, std::defer_lock_t t) noexcept LIBCAMERA_TSA_ACQUIRE(mutex)\n> +\t\t: lock_(mutex.mutex_, t)\n> +\t{\n> +\t}\n> +\n> +\tMutexLocker(Mutex &mutex, std::try_to_lock_t t) noexcept LIBCAMERA_TSA_ACQUIRE(mutex)\n> +\t\t: lock_(mutex.mutex_, t)\n> +\t{\n> +\t}\n> +\n> +\tMutexLocker(Mutex &mutex, std::adopt_lock_t t) noexcept LIBCAMERA_TSA_ACQUIRE(mutex)\n> +\t\t: lock_(mutex.mutex_, t)\n> +\t{\n> +\t}\n> +\n> +\t~MutexLocker() LIBCAMERA_TSA_RELEASE()\n> +\t{\n> +\t}\n> +\n> +\tvoid lock() LIBCAMERA_TSA_ACQUIRE()\n> +\t{\n> +\t\tlock_.lock();\n> +\t}\n> +\n> +\tvoid unlock() LIBCAMERA_TSA_RELEASE()\n> +\t{\n> +\t\tlock_.unlock();\n> +\t}\n> +\n> +\tbool try_lock() LIBCAMERA_TSA_TRY_ACQUIRE(true)\n> +\t{\n> +\t\treturn lock_.try_lock();\n> +\t}\n\nI'd move try_lock() before unlock() to match the order of the\nstd::unique_lock documentation.\n\n> +\n> +private:\n> +\tfriend ConditionVariable;\n> +\n> +\tstd::unique_lock lock_;\n> +};\n> +\n> +class ConditionVariable final\n> +{\n> +public:\n> +\tConditionVariable()\n> +\t{\n> +\t}\n> +\n> +\tvoid notify_one() noexcept\n> +\t{\n> +\t\tcv_.notify_one();\n> +\t}\n> +\n> +\tvoid notify_all() noexcept\n> +\t{\n> +\t\tcv_.notify_all();\n> +\t}\n> +\n> +\ttemplate\n> +\tvoid wait(MutexLocker &locker, Predicate stopWaiting)\n> +\t{\n> +\t\tcv_.wait(locker.lock_, stopWaiting);\n> +\t}\n> +\n> +\ttemplate\n> +\tbool wait_for(MutexLocker &locker,\n> +\t\t const std::chrono::duration &relTime,\n> +\t\t Predicate stopWaiting)\n> +\t{\n> +\t\treturn cv_.wait_for(locker.lock_, relTime, stopWaiting);\n> +\t}\n> +\n> +private:\n> +\tstd::condition_variable cv_;\n> +};\n\nThere are more functions available in std::unique_lock and\nstd::condition_variable, but we can implement them later, if needed.\n\nOne issue we need to address now, however, is documentation. This\ngenerates lots of Doxygen warnings.\n\n> +\n> +} /* namespace libcamera */\n> diff --git a/include/libcamera/base/thread.h b/include/libcamera/base/thread.h\n> index 1ebf8363..44678c34 100644\n> --- a/include/libcamera/base/thread.h\n> +++ b/include/libcamera/base/thread.h\n> @@ -7,15 +7,14 @@\n> \n> #pragma once\n> \n> -#include \n> #include \n> -#include \n> #include \n> #include \n> \n> #include \n> \n> #include \n> +#include \n> #include \n> #include \n> \n> @@ -27,10 +26,6 @@ class Object;\n> class ThreadData;\n> class ThreadMain;\n> \n> -using ConditionVariable = std::condition_variable;\n> -using Mutex = std::mutex;\n> -using MutexLocker = std::unique_lock;\n> -\n> class Thread\n> {\n> public:\n> diff --git a/src/v4l2/v4l2_camera_proxy.h b/src/v4l2/v4l2_camera_proxy.h\n> index 040954dd..23be995d 100644\n> --- a/src/v4l2/v4l2_camera_proxy.h\n> +++ b/src/v4l2/v4l2_camera_proxy.h\n> @@ -14,7 +14,8 @@\n> #include \n> #include \n> \n> -#include \n> +#include \n> +#include \n> \n> #include \n> \n> @@ -59,7 +60,7 @@ private:\n> \tint vidioc_querybuf(V4L2CameraFile *file, struct v4l2_buffer *arg);\n> \tint vidioc_qbuf(V4L2CameraFile *file, struct v4l2_buffer *arg);\n> \tint vidioc_dqbuf(V4L2CameraFile *file, struct v4l2_buffer *arg,\n> -\t\t\t libcamera::Mutex *lock);\n> +\t\t\t libcamera::Mutex *lock) LIBCAMERA_TSA_REQUIRES(*lock);\n> \tint vidioc_streamon(V4L2CameraFile *file, int *arg);\n> \tint vidioc_streamoff(V4L2CameraFile *file, int *arg);\n>","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 81043BDB13\n\tfor ;\n\tTue, 30 Nov 2021 04:18:26 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id EBD9D605B7;\n\tTue, 30 Nov 2021 05:18:25 +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 9BC3F604FC\n\tfor ;\n\tTue, 30 Nov 2021 05:18:24 +0100 (CET)","from pendragon.ideasonboard.com (62-78-145-57.bb.dnainternet.fi\n\t[62.78.145.57])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id E9B368F0;\n\tTue, 30 Nov 2021 05:18:23 +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=\"X1Soplub\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1638245904;\n\tbh=G/zYqSXlbsy51x6bNOymASdog179YV504zhsUuUdvIs=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=X1SoplubPlvQzAF7QbYBEZZubkUo6RFRLiyHncBgS5XY/pMZl5FT+g9ZGbdjRubSJ\n\tXdXw6XGSURvDoAXslnbP2SxGbnPIKBrazSX+EvIIOC+zDbMghVzwagF54wvIz8J1lg\n\tvE2G9MOc0vLg6e4A3WSgDKEs0hTLGAwI+84UBJBs=","Date":"Tue, 30 Nov 2021 06:17:59 +0200","From":"Laurent Pinchart ","To":"Hirokazu Honda ","Message-ID":"","References":"<20211129114453.3186042-1-hiroh@chromium.org>\n\t<20211129114453.3186042-6-hiroh@chromium.org>","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Disposition":"inline","In-Reply-To":"<20211129114453.3186042-6-hiroh@chromium.org>","Subject":"Re: [libcamera-devel] [PATCH v2 05/11] libcamera: base: Add mutex\n\tclasses with thread safety annotations","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","Cc":"libcamera-devel@lists.libcamera.org","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}}]