[Bug 217242] CPU hard lockup related to xhci/dma

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=217242

--- Comment #7 from hps@selasky.org ---
On 4/2/23 00:17, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=217242
> 
> --- Comment #6 from Austin Domino (austin.domino@hotmail.com) ---
> (In reply to Austin Domino from comment #4)
>> The setup that created the output in the previous two attached log files is
>> described in more detail in related posts on:
>>
>> Ubuntu Forums -> https://ubuntuforums.org/showthread.php … st14136903
>> and
>> Ubuntu's Launchpad Bug Page -> https://bugs.launchpad.net/ubuntu/+sour …
>> ug/2013390
> Try 3 (I wish I could edit posts, but I should not have pressed "Save
> Changes"
> so quickly. Sorry about this comment and my incompetence):
> 
> Here are the actual links:
> 
> Ubuntu Forums ->
> https://ubuntuforums.org/showthread.php?t=2485480&p=14136903#post14136903
> and
> Ubuntu's Launchpad Bug Page ->
> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2013390
> 

Hi,

I don't have access to the bugzilla, but this looks like a out of memory 
situation, and does not really point towards the USB XHCI. URB's are 
typically submitted using
GFP_KERNEL, which allow memory allocators to sleep while waiting for 
more memory. GFP_ATOMIC does not allow sleeping.

usb_submit_urb(xxx, GFP_KERNEL);

While that being said, I wish the Linux USB core would take the example 
of the FreeBSD USB core, and pre-allocate all memory needed for USB 
transfers, also called URB's, during device attach. Frequently going 
through allocate and free cycles during operation, is not just 
inefficient, but also greatly degrades the ability to debug the system. 
USB is still quite essential when doing remote server access. Yeah, the 
serial port is great too, but one day inb() and outb() will die :-)

--HPS

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