usb: misc: onboard_hub: Move 'attach' work to the driver
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: 8bc06364 ("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.I16b51f32db0c32f8a8532900bfe1c70c8572881a@changeid Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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