From: Matthias Kaehlcke mka@chromium.org
commit cde37881e2e14590675d0acdfbad408300d9ca95 upstream.
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@i2se.com/ [2] https://lore.kernel.org/all/Y6OrGbqaMy2iVDWB@google.com/
Cc: stable@vger.kernel.org Fixes: 8bc063641ceb ("usb: misc: Add onboard_usb_hub driver") Link: https://lore.kernel.org/r/d04bcc45-3471-4417-b30b-5cf9880d785d@i2se.com/ Link: https://lore.kernel.org/all/Y6OrGbqaMy2iVDWB@google.com/ Reported-by: Stefan Wahren stefan.wahren@i2se.com Signed-off-by: Matthias Kaehlcke mka@chromium.org Link: https://lore.kernel.org/r/20230110172954.v2.2.I16b51f32db0c32f8a8532900bfe1c... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/misc/onboard_usb_hub.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-)
--- 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; };
@@ -271,8 +273,7 @@ static int onboard_hub_probe(struct plat * This needs to be done deferred to avoid self-deadlocks on systems * with nested onboard hubs. */ - INIT_WORK(&hub->attach_usb_driver_work, onboard_hub_attach_usb_driver); - schedule_work(&hub->attach_usb_driver_work); + schedule_work(&attach_usb_driver_work);
return 0; } @@ -285,9 +286,6 @@ static int onboard_hub_remove(struct pla
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 */ @@ -447,6 +445,8 @@ 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);