From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C04BB3F5BFC; Tue, 13 Oct 2026 14:04:53 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791900295; cv=none; b=jTqwiCEW6V/5H8ksKL8RrxtNInB2OLqPh5qMcN8dU/n2nc4KfeGVDndiwH5EzsezmZaEiAbsOBIXx2c5gq292u3FX+dWlrFWjAV5bKNjBCilBVcCSDbuqlgS90H99bGf+trqrr2rL5r5gzoIkYOy+OWHoG2MlEa3UBaxDhRLO4A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791900295; c=relaxed/simple; bh=Ci+V/twvrSuCTaHq3Y2h0sHhVNTrB8cyrxc7c22af1c=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=hoiflv3AZ1a3xsyQCOyu6+pIJVf402yorVsx4DAkeqw3ZtmhAFp7mwM+pfLgu3be9Rtq6N59y3mxeeOBbC7phg9OVHu32Fs6cAuYw3vT2LiekljLAhDJu7PUHhY9HSn8hKLGCNIpcKJS3kly6NnLHimCxWCxV6WAcPx7xg8IGj8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=A7e0u2bR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="A7e0u2bR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 310E21F000FF; Tue, 13 Oct 2026 14:04:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791900293; bh=+65tjF/rN2b9dRPCperIxDap/oLJJZWIgz70YxGogrk=; h=From:To:Cc:Subject:Date; b=A7e0u2bRKyyPdlWu0Mc9DFegqeQ7lnuPpSN2/913zcG5yrYFH24nGy0JBvjFiI/qg 5RXA24/qL4m9v/ll3Td2w/8vPrO6oPLeWSwthHrsnupLmi4cgcC1Bqh/WLeGH2uXNj zwGg6mZ74YPaEiwLMn6FlQnMEeHA78arn5MrBk+45QXP7djLileBSDBJBOrZnr0t9+ HunWiLTy+O+OiNfWDia3lR+tMNkl8q/Lzg+WuKsvKsfRRMKB7TkyYgGbkFuja498zf gPqNyByaVfRzytI6KLilH4tD75tvWP3N7FZst9NWP5+Yd1/X41xBUHtXiHkGvuCIQu GJKVcb5FTjgpQ== Received: from johan by xi.lan with local (Exim 4.99.5) (envelope-from ) id 1xGd7a-000000059AR-36Pr; Tue, 13 Oct 2026 16:04:50 +0200 From: Johan Hovold To: Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Johan Hovold Cc: Dmitry Torokhov , Alan Stern , driver-core@lists.linux.dev, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, Mario Peter Subject: [PATCH v3] driver core: take parent lock in async device attach Date: Tue, 13 Oct 2026 16:04:08 +0200 Message-ID: <20261013140408.1226841-1-johan@kernel.org> X-Mailer: git-send-email 2.55.0 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Mario Peter On buses with need_parent_lock set (only USB), probe() must run with the parent device locked. A synchronous attach after device_add() gets this from the caller, e.g. usb_set_configuration() holds the udev lock while adding interfaces. __device_attach_async_helper() runs the probe from an async worker instead, where that lock isn't held, and only takes device_lock(dev). With async probing enabled for the hub driver (e.g. driver_async_probe=* or driver_async_probe=hub), this races when a multi-TT hub is configured. For multi-TT hubs, hub_probe() calls usb_set_interface(hdev, 0, 1) to select the TT-per-port altsetting, and usb_set_interface() creates the endpoint devices of the interface a second time: usb_set_configuration() async worker [udev locked] device_add(intf) queues the probe ----------> __device_attach_async_helper() [intf locked, udev not locked] hub_probe() usb_set_interface(hdev, 0, 1) create_intf_ep_devs(intf) create_intf_ep_devs(intf) create_intf_ep_devs() checks and sets intf->ep_devs_created without a lock of its own. If usb_set_configuration() has created ep_81 but not yet set the flag, usb_set_interface() skips removing the endpoint devices of the old altsetting and creates ep_81 again. With a synchronous probe, hub_probe() runs inside device_add() with the udev lock held, and usb_set_configuration() then finds ep_devs_created already set. Single-TT hubs don't call usb_set_interface() from hub_probe() and don't show this warning, but their probe runs without the udev lock as well. On an i.MX8MM board with an onboard USB2514 hub this hit 11 of 100 boots: sysfs: cannot create duplicate filename '.../1-1/1-1:1.0/ep_81' Call trace: sysfs_warn_dup usb_create_ep_devs create_intf_ep_devs usb_set_interface hub_probe usb_probe_interface really_probe __device_attach_async_helper async_run_entry_fn It also shows on v7.3-rc6 in QEMU, with dummy_hcd and a raw-gadget program emulating a multi-TT hub: re-authorizing the hub in a loop, while a SCHED_FIFO task preempts the writing task at random points for 3 ms, hit the warning in 29 of 6000 iterations. Take the parent lock in __device_attach_async_helper() as well, like __driver_attach_async_helper() does, and move __device_driver_lock/unlock() up for that. With this the warning was gone in 300 boots on the board and in 6000 iterations in QEMU. Fixes: 765230b5f084 ("driver-core: add asynchronous probing support for drivers") Assisted-by: LLM Signed-off-by: Mario Peter [ johan: switch to async_schedule_dev_nocall() to avoid deadlock if async_schedule_dev() runs synchronously when parent lock is held ] Signed-off-by: Johan Hovold --- Changes in v3: - fix deadlock if async_schedule_dev() runs synchronously v2: https://lore.kernel.org/all/20261007131514.1260696-1-mario.peter@leica-geosystems.com/ v1: https://lore.kernel.org/all/20261006132335.4014316-1-mario.peter@leica-geosystems.com/ drivers/base/dd.c | 85 ++++++++++++++++++++++++++--------------------- 1 file changed, 47 insertions(+), 38 deletions(-) diff --git a/drivers/base/dd.c b/drivers/base/dd.c index f6525a7ee8c5..9dc7cce9bd8d 100644 --- a/drivers/base/dd.c +++ b/drivers/base/dd.c @@ -1029,6 +1029,38 @@ static int __device_attach_driver(struct device_driver *drv, void *_data) return ret == 0; } +/* + * __device_driver_lock - acquire locks needed to manipulate dev->drv + * @dev: Device we will update driver info for + * @parent: Parent device. Needed if the bus requires parent lock + * + * This function will take the required locks for manipulating dev->drv. + * Normally this will just be the @dev lock, but when called for a USB + * interface, @parent lock will be held as well. + */ +static void __device_driver_lock(struct device *dev, struct device *parent) +{ + if (parent && dev->bus->need_parent_lock) + device_lock(parent); + device_lock(dev); +} + +/* + * __device_driver_unlock - release locks needed to manipulate dev->drv + * @dev: Device we will update driver info for + * @parent: Parent device. Needed if the bus requires parent lock + * + * This function will release the required locks for manipulating dev->drv. + * Normally this will just be the @dev lock, but when called for a + * USB interface, @parent lock will be released as well. + */ +static void __device_driver_unlock(struct device *dev, struct device *parent) +{ + device_unlock(dev); + if (parent && dev->bus->need_parent_lock) + device_unlock(parent); +} + static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) { struct device *dev = _dev; @@ -1038,7 +1070,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) .want_async = true, }; - device_lock(dev); + __device_driver_lock(dev, dev->parent); /* * Check if device has already been removed or claimed. This may @@ -1060,7 +1092,7 @@ static void __device_attach_async_helper(void *_dev, async_cookie_t cookie) if (dev->parent) pm_runtime_put(dev->parent); out_unlock: - device_unlock(dev); + __device_driver_unlock(dev, dev->parent); put_device(dev); } @@ -1117,8 +1149,13 @@ static int __device_attach(struct device *dev, bool allow_async) } out_unlock: device_unlock(dev); - if (async) - async_schedule_dev(__device_attach_async_helper, dev); + if (async) { + if (!async_schedule_dev_nocall(__device_attach_async_helper, dev)) { + put_device(dev); + ret = 2; /* retry synchronously */ + } + } + return ret; } @@ -1145,48 +1182,20 @@ EXPORT_SYMBOL_GPL(device_attach); void device_initial_probe(struct device *dev) { struct subsys_private *sp = bus_to_subsys(dev->bus); + int ret; if (!sp) return; - if (sp->drivers_autoprobe) - __device_attach(dev, true); + if (sp->drivers_autoprobe) { + ret = __device_attach(dev, true); + if (ret == 2) + __device_attach(dev, false); + } subsys_put(sp); } -/* - * __device_driver_lock - acquire locks needed to manipulate dev->drv - * @dev: Device we will update driver info for - * @parent: Parent device. Needed if the bus requires parent lock - * - * This function will take the required locks for manipulating dev->drv. - * Normally this will just be the @dev lock, but when called for a USB - * interface, @parent lock will be held as well. - */ -static void __device_driver_lock(struct device *dev, struct device *parent) -{ - if (parent && dev->bus->need_parent_lock) - device_lock(parent); - device_lock(dev); -} - -/* - * __device_driver_unlock - release locks needed to manipulate dev->drv - * @dev: Device we will update driver info for - * @parent: Parent device. Needed if the bus requires parent lock - * - * This function will release the required locks for manipulating dev->drv. - * Normally this will just be the @dev lock, but when called for a - * USB interface, @parent lock will be released as well. - */ -static void __device_driver_unlock(struct device *dev, struct device *parent) -{ - device_unlock(dev); - if (parent && dev->bus->need_parent_lock) - device_unlock(parent); -} - /** * device_driver_attach - attach a specific driver to a specific device * @drv: Driver to attach -- 2.55.0