Messages in this thread | | | Date | Tue, 5 Jul 2022 20:38:48 +0200 | Subject | Re: [PATCH] Bluetooth: core: Fix deadlock due to `cancel_work_sync(&hdev->power_on)` from hci_power_on_sync. | From | Mateusz Jończyk <> |
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W dniu 5.07.2022 o 14:59, Vasyl Vavrychuk pisze: > `cancel_work_sync(&hdev->power_on)` was moved to hci_dev_close_sync in > commit [1] to ensure that power_on work is canceled after HCI interface > down. > > But, in certain cases power_on work function may call hci_dev_close_sync > itself: hci_power_on -> hci_dev_do_close -> hci_dev_close_sync -> > cancel_work_sync(&hdev->power_on), causing deadlock. In particular, this > happens when device is rfkilled on boot. To avoid deadlock, move > power_on work canceling out of hci_dev_do_close/hci_dev_close_sync. > > Deadlock introduced by commit [1] was reported in [2,3] as broken > suspend. Suspend did not work because `hdev->req_lock` held as result of > `power_on` work deadlock. In fact, other BT features were not working. > It was not observed when testing [1] since it was verified without > rfkill in place. > > NOTE: It is not needed to cancel power_on work from other places where > hci_dev_do_close/hci_dev_close_sync is called in case: > * Requests were serialized due to `hdev->req_workqueue`. The power_on > work is first in that workqueue. > * hci_rfkill_set_block which won't close device anyway until HCI_SETUP > is on. > * hci_sock_release which runs after hci_sock_bind which ensures > HCI_SETUP was cleared. > > As result, behaviour is the same as in pre-dd06ed7 commit, except > power_on work cancel added to hci_dev_close. > > [1]: commit dd06ed7ad057 ("Bluetooth: core: Fix missing power_on work cancel on HCI close") > [2]: https://lore.kernel.org/lkml/20220614181706.26513-1-max.oss.09@gmail.com/ > [2]: https://lore.kernel.org/lkml/1236061d-95dd-c3ad-a38f-2dae7aae51ef@o2.pl/ > > Fixes: commit dd06ed7ad057 ("Bluetooth: core: Fix missing power_on work cancel on HCI close") > Signed-off-by: Vasyl Vavrychuk <vasyl.vavrychuk@opensynergy.com> > Reported-by: Max Krummenacher <max.krummenacher@toradex.com> > Reported-by: Mateusz Jonczyk <mat.jonczyk@o2.pl>
Works well: suspend (with bluetooth on and also off), hibernation, sending files, rfkill.
Thank you.
Reported-and-tested-by: Mateusz Jończyk <mat.jonczyk@o2.pl>
Greetings,
Mateusz Jończyk
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