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{ "id": 2111, "url": "https://patchwork.libcamera.org/api/patches/2111/?format=api", "web_url": "https://patchwork.libcamera.org/patch/2111/", "project": { "id": 1, "url": "https://patchwork.libcamera.org/api/projects/1/?format=api", "name": "libcamera", "link_name": "libcamera", "list_id": "libcamera_core", "list_email": "libcamera-devel@lists.libcamera.org", "web_url": "", "scm_url": "", "webscm_url": "" }, "msgid": "<20191006053226.8976-7-laurent.pinchart@ideasonboard.com>", "date": "2019-10-06T05:32:23", "name": "[libcamera-devel,6/9] libcamera: timer: Forbid starting or stopping timer from another thread", "commit_ref": null, "pull_url": null, "state": "accepted", "archived": false, "hash": "d841c588e3799286404bd75d412be4cf010ec95f", "submitter": { "id": 2, "url": "https://patchwork.libcamera.org/api/people/2/?format=api", "name": "Laurent Pinchart", "email": "laurent.pinchart@ideasonboard.com" }, "delegate": null, "mbox": "https://patchwork.libcamera.org/patch/2111/mbox/", "series": [ { "id": 522, "url": "https://patchwork.libcamera.org/api/series/522/?format=api", "web_url": "https://patchwork.libcamera.org/project/libcamera/list/?series=522", "date": "2019-10-06T05:32:17", "name": "Timer fixes and enhancements", "version": 1, "mbox": "https://patchwork.libcamera.org/series/522/mbox/" } ], "comments": "https://patchwork.libcamera.org/api/patches/2111/comments/", "check": "pending", "checks": "https://patchwork.libcamera.org/api/patches/2111/checks/", "tags": {}, "headers": { "Return-Path": "<laurent.pinchart@ideasonboard.com>", "Received": [ "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 3A4C66196E\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tSun, 6 Oct 2019 07:32:39 +0200 (CEST)", "from pendragon.ideasonboard.com\n\t(modemcable151.96-160-184.mc.videotron.ca [184.160.96.151])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 99EE2DD\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tSun, 6 Oct 2019 07:32:38 +0200 (CEST)" ], "DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1570339958;\n\tbh=KVVAKqGdxut9JHBGlZQRoDo4n+8wG0LViVGNO9UV+18=;\n\th=From:To:Subject:Date:In-Reply-To:References:From;\n\tb=NkKnb1+DROYRB0bLbKiVRc2sTKGCve3noWzz63H2jQTX51Nss5nlFUm3rPfO45SWF\n\t9RLDATMFWw8teWcXmeSshXs/C2yZRnQRk0NqQAEwTBmb6+YgEOXQTGK1uzkW3Sb97o\n\td7PabWwCURQWBmE3x+WTeHkxB05qF5N4X53JExe8=", "From": "Laurent Pinchart <laurent.pinchart@ideasonboard.com>", "To": "libcamera-devel@lists.libcamera.org", "Date": "Sun, 6 Oct 2019 08:32:23 +0300", "Message-Id": "<20191006053226.8976-7-laurent.pinchart@ideasonboard.com>", "X-Mailer": "git-send-email 2.21.0", "In-Reply-To": "<20191006053226.8976-1-laurent.pinchart@ideasonboard.com>", "References": "<20191006053226.8976-1-laurent.pinchart@ideasonboard.com>", "MIME-Version": "1.0", "Content-Transfer-Encoding": "8bit", "Subject": "[libcamera-devel] [PATCH 6/9] libcamera: timer: Forbid starting or\n\tstopping timer from another thread", "X-BeenThere": "libcamera-devel@lists.libcamera.org", "X-Mailman-Version": "2.1.29", "Precedence": "list", "List-Id": "<libcamera-devel.lists.libcamera.org>", "List-Unsubscribe": "<https://lists.libcamera.org/options/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=unsubscribe>", "List-Archive": "<https://lists.libcamera.org/pipermail/libcamera-devel/>", "List-Post": "<mailto:libcamera-devel@lists.libcamera.org>", "List-Help": "<mailto:libcamera-devel-request@lists.libcamera.org?subject=help>", "List-Subscribe": "<https://lists.libcamera.org/listinfo/libcamera-devel>,\n\t<mailto:libcamera-devel-request@lists.libcamera.org?subject=subscribe>", "X-List-Received-Date": "Sun, 06 Oct 2019 05:32:39 -0000" }, "content": "Starting or stopping a timer from a different thread than the one it\nbelongs to is inherently racy. Disallow it.\n\nSigned-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>\n---\n src/libcamera/timer.cpp | 24 +++++++++++++++++++++---\n 1 file changed, 21 insertions(+), 3 deletions(-)", "diff": "diff --git a/src/libcamera/timer.cpp b/src/libcamera/timer.cpp\nindex 5d4e52713e6e..8749d66c8662 100644\n--- a/src/libcamera/timer.cpp\n+++ b/src/libcamera/timer.cpp\n@@ -36,6 +36,11 @@ LOG_DEFINE_CATEGORY(Timer)\n * Once started the timer will run until it times out. It can be stopped with\n * stop(), and once it times out or is stopped, can be started again with\n * start().\n+ *\n+ * Timers run in the thread they belong to, and thus emit the \\a ref timeout\n+ * signal from that thread. To avoid race conditions they must not be started\n+ * or stopped from a different thread, attempts to do so will be rejected and\n+ * logged, and may cause undefined behaviour.\n */\n \n /**\n@@ -57,17 +62,24 @@ Timer::~Timer()\n * \\brief Start or restart the timer with a timeout of \\a msec\n * \\param[in] msec The timer duration in milliseconds\n *\n- * If the timer is already running it will be stopped and restarted.\n+ * This method shall be called from the thread the timer is associated with. If\n+ * the timer is already running it will be stopped and restarted.\n */\n \n /**\n * \\brief Start or restart the timer with a timeout of \\a duration\n * \\param[in] duration The timer duration in milliseconds\n *\n- * If the timer is already running it will be stopped and restarted.\n+ * This method shall be called from the thread the timer is associated with. If\n+ * the timer is already running it will be stopped and restarted.\n */\n void Timer::start(std::chrono::milliseconds duration)\n {\n+\tif (Thread::current() != thread()) {\n+\t\tLOG(Timer, Error) << \"Timer can't be started from another thread\";\n+\t\treturn;\n+\t}\n+\n \tdeadline_ = utils::clock::now() + duration;\n \n \tLOG(Timer, Debug)\n@@ -87,13 +99,19 @@ void Timer::start(std::chrono::milliseconds duration)\n * After this function returns the timer is guaranteed not to emit the\n * \\ref timeout signal.\n *\n- * If the timer is not running this function performs no operation.\n+ * This method shall be called from the thread the timer is associated with. If\n+ * the timer is not running this function performs no operation.\n */\n void Timer::stop()\n {\n \tif (!isRunning())\n \t\treturn;\n \n+\tif (Thread::current() != thread()) {\n+\t\tLOG(Timer, Error) << \"Timer can't be stopped from another thread\";\n+\t\treturn;\n+\t}\n+\n \tunregisterTimer();\n }\n \n", "prefixes": [ "libcamera-devel", "6/9" ] }