Hi Matthias,
Am 06.01.23 um 00:03 schrieb Matthias Kaehlcke:
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.
i applied both patches for this series on top of v6.1 (multi_v7_defconfig), but usb is still broken on Raspberry Pi 3 B+
Best regards
[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
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);