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`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]: commitff7f292611("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:ff7f292611("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> Tested-by: Max Krummenacher <max.krummenacher@toradex.com> Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.