Messages in this thread |  | | Date | Sat, 7 Jan 2023 18:23:12 +0100 | Subject | Re: [PATCH 2/2] usb: misc: onboard_hub: Move 'attach' work to the driver | From | Stefan Wahren <> |
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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); >
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