From patchwork Mon Dec 8 11:00:35 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: 25388 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 B58DDBDDFC for ; Mon, 8 Dec 2025 11:00:45 +0000 (UTC) Received: from lancelot.ideasonboard.com (localhost [IPv6:::1]) by lancelot.ideasonboard.com (Postfix) with ESMTP id B4FC461406; Mon, 8 Dec 2025 12:00:43 +0100 (CET) Authentication-Results: lancelot.ideasonboard.com; dkim=pass (1024-bit key; unprotected) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="sUuDe+3n"; dkim-atps=neutral Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lancelot.ideasonboard.com (Postfix) with ESMTPS id 9B4D8613F7 for ; Mon, 8 Dec 2025 12:00:40 +0100 (CET) Received: from pb-laptop.local (185.221.142.68.nat.pool.zt.hu [185.221.142.68]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 321F0C7A; Mon, 8 Dec 2025 11:58:21 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1765191501; bh=D1liksjrLRPHgt0evjnO37S4z3Yg2269EbVTF3HMU3Q=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=sUuDe+3nirVoYftnNVI1V8CijNdGJtp1xt3Q9IulbybP/PnXaV1tC0zae8F93TmLu yNhmLE78v3NBIh6sUY1HZ4bEdw03n16qPZyGslBBcCVm/jWTWQSKDyGDI2nSq58Dyx tOE6hpAK7Hz6/WSIsMkSOd+ld/wUiGVDj0xmuW4Y= From: =?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= To: libcamera-devel@lists.libcamera.org Cc: Kieran Bingham , Laurent Pinchart Subject: [RFC PATCH v2 3/3] libcamera: device_enumerator_udev: Handle duplicate devices Date: Mon, 8 Dec 2025 12:00:35 +0100 Message-ID: <20251208110035.248881-3-barnabas.pocze@ideasonboard.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20251208110035.248881-1-barnabas.pocze@ideasonboard.com> References: <20251208110035.248881-1-barnabas.pocze@ideasonboard.com> 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" It is possible that same device is processed multiple times, leading to multiple `MediaDevice`s being instantiated, mostly likely leading to a fatal error: Trying to register a camera with a duplicated ID xyzw... There is a time window after the `udev_monitor` has been created in `init()` and the first (and only) enumeration done in `enumerate()`. If e.g. a UVC camera is connected in this time frame, then it is possible that it will be processed both by the `udevNotify()` and the initial `enumerate()`, leading to the fatal error. This can be reproduced as follows: 1. $ gdb --args cam -m 2. (gdb) break libcamera::DeviceEnumeratorUdev::enumerate 3. (gdb) run 4. when the breakpoint is hit, connect a usb camera 5. (gdb) continue 6. observe fatal error To address this, keep track of the devnums of all devices reported by udev, and reject devices with already known devnums. This ensures that the same device won't be reported multiple times (assuming that udev reports "add" / "remove" events in the correct order). Closes: https://gitlab.freedesktop.org/camera/libcamera/-/issues/293 Signed-off-by: Barnabás Pőcze Reviewed-by: Kieran Bingham Reviewed-by: Laurent Pinchart --- changes in v2: * address review comments v1: https://patchwork.libcamera.org/patch/25336/ --- .../internal/device_enumerator_udev.h | 3 ++ src/libcamera/device_enumerator_udev.cpp | 38 ++++++++++++++----- 2 files changed, 32 insertions(+), 9 deletions(-) -- 2.52.0 diff --git a/include/libcamera/internal/device_enumerator_udev.h b/include/libcamera/internal/device_enumerator_udev.h index c2f7154b6b..958e27a2f1 100644 --- a/include/libcamera/internal/device_enumerator_udev.h +++ b/include/libcamera/internal/device_enumerator_udev.h @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -59,6 +60,7 @@ private: LIBCAMERA_DISABLE_COPY_AND_MOVE(DeviceEnumeratorUdev) int addUdevDevice(struct udev_device *dev); + void removeUdevDevice(struct udev_device *dev); int populateMediaDevice(MediaDevice *media, DependencyMap *deps); std::string lookupDeviceNode(dev_t devnum); @@ -70,6 +72,7 @@ private: EventNotifier *notifier_; std::set orphans_; + std::unordered_set devices_; std::list pending_; std::map devMap_; }; diff --git a/src/libcamera/device_enumerator_udev.cpp b/src/libcamera/device_enumerator_udev.cpp index 4e20a3cc0c..3195dd06e2 100644 --- a/src/libcamera/device_enumerator_udev.cpp +++ b/src/libcamera/device_enumerator_udev.cpp @@ -76,6 +76,21 @@ int DeviceEnumeratorUdev::addUdevDevice(struct udev_device *dev) if (!subsystem) return -ENODEV; + /* + * Record that udev reported the given devnum. And reject if it has + * already been seen (e.g. device added between udev monitor creation + * in `init()` and `enumerate()`). This record is kept even if later + * in this function an error is encountered. Only a "remove" event + * from udev should erase it from `devices_`. + */ + const dev_t devnum = udev_device_get_devnum(dev); + if (devnum == makedev(0, 0)) + return -ENODEV; + + const auto [it, inserted] = devices_.insert(devnum); + if (!inserted) + return -EEXIST; + if (!strcmp(subsystem, "media")) { std::unique_ptr media = createDevice(udev_device_get_devnode(dev)); @@ -111,13 +126,22 @@ int DeviceEnumeratorUdev::addUdevDevice(struct udev_device *dev) } if (!strcmp(subsystem, "video4linux")) { - addV4L2Device(udev_device_get_devnum(dev)); + addV4L2Device(devnum); return 0; } return -ENODEV; } +void DeviceEnumeratorUdev::removeUdevDevice(struct udev_device *dev) +{ + const char *subsystem = udev_device_get_subsystem(dev); + if (subsystem && !strcmp(subsystem, "media")) + removeDevice(udev_device_get_devnode(dev)); + + devices_.erase(udev_device_get_devnum(dev)); +} + int DeviceEnumeratorUdev::enumerate() { struct udev_enumerate *udev_enum = nullptr; @@ -341,18 +365,14 @@ void DeviceEnumeratorUdev::udevNotify() } std::string_view action(udev_device_get_action(dev)); - std::string_view deviceNode(udev_device_get_devnode(dev)); LOG(DeviceEnumerator, Debug) - << action << " device " << deviceNode; + << action << " device " << udev_device_get_devnode(dev); - if (action == "add") { + if (action == "add") addUdevDevice(dev); - } else if (action == "remove") { - const char *subsystem = udev_device_get_subsystem(dev); - if (subsystem && !strcmp(subsystem, "media")) - removeDevice(std::string(deviceNode)); - } + else if (action == "remove") + removeUdevDevice(dev); udev_device_unref(dev); }