Currently each onboard_hub platform device owns an 'attach' work, which is scheduled when the device probes. With this deadlocks have been reported on a Raspberry Pi 3 B+ [1], which has nested onboard hubs. The flow of the deadlock is something like this (with the onboard_hub driver built as a module) [2]: - USB root hub is instantiated - core hub driver calls onboard_hub_create_pdevs(), which creates the 'raw' platform device for the 1st level hub - 1st level hub is probed by the core hub driver - core hub driver calls onboard_hub_create_pdevs(), which creates the 'raw' platform device for the 2nd level hub - onboard_hub platform driver is registered - platform device for 1st level hub is probed - schedules 'attach' work - platform device for 2nd level hub is probed - schedules 'attach' work - onboard_hub USB driver is registered - device (and parent) lock of hub is held while the device is re-probed with the onboard_hub driver - 'attach' work (running in another thread) calls driver_attach(), which blocks on one of the hub device locks - onboard_hub_destroy_pdevs() is called by the core hub driver when one of the hubs is detached - destroying the pdevs invokes onboard_hub_remove(), which waits for the 'attach' work to complete - waits forever, since the 'attach' work can't acquire the device lock Use a single work struct for the driver instead of having a work struct per onboard hub platform driver instance. With that it isn't necessary to cancel the work in onboard_hub_remove(), which fixes the deadlock. The work is only cancelled when the driver is unloaded. [1] https://lore.kernel.org/r/d04bcc45-3471-4417-b30b-5cf9880d785d@xxxxxxxx/ [2] https://lore.kernel.org/all/Y6OrGbqaMy2iVDWB@xxxxxxxxxx/ Cc: stable@xxxxxxxxxxxxxxx Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver") Link: https://lore.kernel.org/r/d04bcc45-3471-4417-b30b-5cf9880d785d@xxxxxxxx/ Link: https://lore.kernel.org/all/Y6OrGbqaMy2iVDWB@xxxxxxxxxx/ Reported-by: Stefan Wahren <stefan.wahren@xxxxxxxx> Signed-off-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx> --- drivers/usb/misc/onboard_usb_hub.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c index db0844b30bbd..8bc4deb465f0 100644 --- a/drivers/usb/misc/onboard_usb_hub.c +++ b/drivers/usb/misc/onboard_usb_hub.c @@ -27,7 +27,10 @@ #include "onboard_usb_hub.h" +static void onboard_hub_attach_usb_driver(struct work_struct *work); + static struct usb_device_driver onboard_hub_usbdev_driver; +static DECLARE_WORK(attach_usb_driver_work, onboard_hub_attach_usb_driver); /************************** Platform driver **************************/ @@ -45,7 +48,6 @@ struct onboard_hub { bool is_powered_on; bool going_away; struct list_head udev_list; - struct work_struct attach_usb_driver_work; struct mutex lock; }; @@ -270,9 +272,15 @@ static int onboard_hub_probe(struct platform_device *pdev) * * This needs to be done deferred to avoid self-deadlocks on systems * with nested onboard hubs. + * + * If the work is already running wait for it to complete, then + * schedule it again to ensure that the USB devices of this onboard + * hub instance are bound to the USB driver. */ - INIT_WORK(&hub->attach_usb_driver_work, onboard_hub_attach_usb_driver); - schedule_work(&hub->attach_usb_driver_work); + while (work_busy(&attach_usb_driver_work) & WORK_BUSY_RUNNING) + msleep(10); + + schedule_work(&attach_usb_driver_work); return 0; } @@ -285,9 +293,6 @@ static int onboard_hub_remove(struct platform_device *pdev) hub->going_away = true; - if (&hub->attach_usb_driver_work != current_work()) - cancel_work_sync(&hub->attach_usb_driver_work); - mutex_lock(&hub->lock); /* unbind the USB devices to avoid dangling references to this device */ @@ -449,6 +454,8 @@ static void __exit onboard_hub_exit(void) { usb_deregister_device_driver(&onboard_hub_usbdev_driver); platform_driver_unregister(&onboard_hub_driver); + + cancel_work_sync(&attach_usb_driver_work); } module_exit(onboard_hub_exit); -- 2.39.0.314.g84b9a713c41-goog
