{"id":24164,"url":"https://patchwork.libcamera.org/api/patches/24164/?format=json","web_url":"https://patchwork.libcamera.org/patch/24164/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/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":"<20250820080632.106505-1-barnabas.pocze@ideasonboard.com>","date":"2025-08-20T08:06:32","name":"[RFC,v2] apps: cam: Use signalfd","commit_ref":null,"pull_url":null,"state":"accepted","archived":false,"hash":"4090186379d1c35ef0a9ac5633c797c1c46739a9","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/24164/mbox/","series":[{"id":5395,"url":"https://patchwork.libcamera.org/api/series/5395/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5395","date":"2025-08-20T08:06:32","name":"[RFC,v2] apps: cam: Use signalfd","version":2,"mbox":"https://patchwork.libcamera.org/series/5395/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/24164/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/24164/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 CFBFCBEFBE\n\tfor ;\n\tWed, 20 Aug 2025 08:06:38 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id DE20F692D7;\n\tWed, 20 Aug 2025 10:06:37 +0200 (CEST)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 9D0A2613C5\n\tfor ;\n\tWed, 20 Aug 2025 10:06:36 +0200 (CEST)","from pb-laptop.local (185.221.141.188.nat.pool.zt.hu\n\t[185.221.141.188])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id D8DF36AF;\n\tWed, 20 Aug 2025 10:05:37 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"dfBJVqK+\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1755677138;\n\tbh=z4ZIBoRN6ehN+fx5CBr7pRlBc2PEZr2Qt0VxB77FMOw=;\n\th=From:To:Subject:Date:From;\n\tb=dfBJVqK+7/nw4Etf1gtHD05MoKhy6XXXVoMdPyW7uAVm6v2NwxzVxPwhz9dmgOWhq\n\t7sS0s1apyQH0WVBvn8NPAxsNZ1vqzP6QyadSvW30/6hUgybohsYFlQO6c0CmmWrc3j\n\t2t6i1Bfr1Q95otcOW7eN1NG0cqmb+a6FZiSbzlGA=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org,\n\tPaul Elder ","Subject":"[RFC PATCH v2] apps: cam: Use signalfd","Date":"Wed, 20 Aug 2025 10:06:32 +0200","Message-ID":"<20250820080632.106505-1-barnabas.pocze@ideasonboard.com>","X-Mailer":"git-send-email 2.50.1","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":"","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":"Use a signalfd to detect `SIGINT` instead of registering a signal handler\nin order to remove the `CamApp` singleton. This is better than using a\nnormal signal handler: a signal can arrive after the `CamApp` object has\nbeen destroyed, leading to a use-after-free. Modifying the `CamApp::app_`\nin the destructor is not a good alternative because that would not be async\nsignal safe (unless it is made atomic).\n\nSigned-off-by: Barnabás Pőcze \n---\nchanges in v2:\n\t* move into `CamApp::init()`\n\t* use `pthread_sigmask()` instead of `sigprocmask()`\n\nv1: https://patchwork.libcamera.org/patch/24144/\n---\n src/apps/cam/main.cpp | 57 ++++++++++++++++++----------------------\n src/apps/cam/meson.build | 1 +\n 2 files changed, 26 insertions(+), 32 deletions(-)\n\n--\n2.50.1","diff":"diff --git a/src/apps/cam/main.cpp b/src/apps/cam/main.cpp\nindex a1788b7a9..91a29736f 100644\n--- a/src/apps/cam/main.cpp\n+++ b/src/apps/cam/main.cpp\n@@ -10,8 +10,10 @@\n #include \n #include \n #include \n+#include \n #include \n #include \n+#include \n\n #include \n #include \n@@ -29,13 +31,10 @@ class CamApp\n public:\n \tCamApp();\n\n-\tstatic CamApp *instance();\n-\n \tint init(int argc, char **argv);\n \tvoid cleanup();\n\n \tint exec();\n-\tvoid quit();\n\n private:\n \tvoid cameraAdded(std::shared_ptr cam);\n@@ -46,32 +45,45 @@ private:\n\n \tstatic std::string cameraName(const Camera *camera);\n\n-\tstatic CamApp *app_;\n \tOptionsParser::Options options_;\n\n+\tUniqueFD signalFd_;\n+\n \tstd::unique_ptr cm_;\n\n \tstd::atomic_uint loopUsers_;\n \tEventLoop loop_;\n };\n\n-CamApp *CamApp::app_ = nullptr;\n-\n CamApp::CamApp()\n \t: loopUsers_(0)\n {\n-\tCamApp::app_ = this;\n-}\n-\n-CamApp *CamApp::instance()\n-{\n-\treturn CamApp::app_;\n }\n\n int CamApp::init(int argc, char **argv)\n {\n+\tsigset_t ss;\n \tint ret;\n\n+\tsigemptyset(&ss);\n+\tsigaddset(&ss, SIGINT);\n+\n+\tret = -pthread_sigmask(SIG_BLOCK, &ss, nullptr);\n+\tif (ret < 0)\n+\t\treturn ret;\n+\n+\tsignalFd_.reset(signalfd(-1, &ss, SFD_CLOEXEC | SFD_NONBLOCK));\n+\tif (!signalFd_.isValid())\n+\t\treturn -errno;\n+\n+\tloop_.addFdEvent(signalFd_.get(), EventLoop::Read, [this] {\n+\t\tsignalfd_siginfo si;\n+\t\tstd::ignore = read(signalFd_.get(), &si, sizeof(si));\n+\n+\t\tstd::cout << \"Exiting\" << std::endl;\n+\t\tloop_.exit();\n+\t});\n+\n \tret = parseOptions(argc, argv);\n \tif (ret < 0)\n \t\treturn ret;\n@@ -103,11 +115,6 @@ int CamApp::exec()\n \treturn ret;\n }\n\n-void CamApp::quit()\n-{\n-\tloop_.exit();\n-}\n-\n int CamApp::parseOptions(int argc, char *argv[])\n {\n \tStreamKeyValueParser streamKeyValue;\n@@ -205,7 +212,7 @@ void CamApp::cameraRemoved(std::shared_ptr cam)\n void CamApp::captureDone()\n {\n \tif (--loopUsers_ == 0)\n-\t\tEventLoop::instance()->exit(0);\n+\t\tloop_.exit(0);\n }\n\n int CamApp::run()\n@@ -345,16 +352,6 @@ std::string CamApp::cameraName(const Camera *camera)\n \treturn name;\n }\n\n-namespace {\n-\n-void signalHandler([[maybe_unused]] int signal)\n-{\n-\tstd::cout << \"Exiting\" << std::endl;\n-\tCamApp::instance()->quit();\n-}\n-\n-} /* namespace */\n-\n int main(int argc, char **argv)\n {\n \tCamApp app;\n@@ -364,10 +361,6 @@ int main(int argc, char **argv)\n \tif (ret)\n \t\treturn ret == -EINTR ? 0 : EXIT_FAILURE;\n\n-\tstruct sigaction sa = {};\n-\tsa.sa_handler = &signalHandler;\n-\tsigaction(SIGINT, &sa, nullptr);\n-\n \tif (app.exec())\n \t\treturn EXIT_FAILURE;\n\ndiff --git a/src/apps/cam/meson.build b/src/apps/cam/meson.build\nindex 2833c86e9..cd7f120f9 100644\n--- a/src/apps/cam/meson.build\n+++ b/src/apps/cam/meson.build\n@@ -56,6 +56,7 @@ cam = executable('cam', cam_sources,\n libjpeg,\n libsdl2,\n libtiff,\n+ libthreads,\n libyaml,\n ],\n cpp_args : cam_cpp_args,\n","prefixes":["RFC","v2"]}