Re: [patch]race condition in btusb disconnect() handling

Am Dienstag 19 August 2008 15:28:26 schrieb Marcel Holtmann:
Hello,

Hi Oliver,

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btusb has some races in disconnect()

- it doesn't deal with only the iso interface disconnected

It see the point here, but then we have to release the main interface
cleanly or just disable SCO. I would prefer to just disable SCO.

The patch disables the main interface. Just disabling SCO means that
btusb_data.isoc could no longer be treated as constant and locking for it
would be necessary. This seems extravagant for a minor use case.

I am fine with both ways. Will decide which code looks cleaner :)

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- it releases the data interface before unregistering the iso interface

How does this happen? It doesn't do it that way.

From your version:
	if (data->isoc)
		usb_driver_release_interface(&btusb_driver, data->isoc);

	usb_set_intfdata(intf, NULL);

	hci_unregister_dev(hdev);

First you release the interface, then you unregister the hci.

Putting it after hci_unregister_dev is an issue. The unregister will
call __hci_dev_put and then in return will call the destruct callback
which will free the data pointer.

So either we use hci_dev_hold or make sure that disconnect can only
disable the SCO interface. That comes directly with the first comment
from you.

I'll make a patch with hci_dev_hold. It seems the cleaner solution.

	Regards
		Oliver