mainlining shenanigans
c91815b596
This is a requirement which has always existed but, somehow, wasn't
reflected in the documentation and problems weren't found until now
when Tuba Yavuz found a possible deadlock happening between dwc3 and
f_hid. She described the situation as follows:
spin_lock_irqsave(&hidg->write_spinlock, flags); // first acquire
/* we our function has been disabled by host */
if (!hidg->req) {
free_ep_req(hidg->in_ep, hidg->req);
goto try_again;
}
[...]
status = usb_ep_queue(hidg->in_ep, hidg->req, GFP_ATOMIC);
=>
[...]
=> usb_gadget_giveback_request
=>
f_hidg_req_complete
=>
spin_lock_irqsave(&hidg->write_spinlock, flags); // second acquire
Note that this happens because dwc3 would call ->complete() on a
failed usb_ep_queue() due to failed Start Transfer command. This is,
anyway, a theoretical situation because dwc3 currently uses "No
Response Update Transfer" command for Bulk and Interrupt endpoints.
It's still good to make this case impossible to happen even if the "No
Reponse Update Transfer" command is changed.
Reported-by: Tuba Yavuz <tuba@ece.ufl.edu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| README | ||
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.