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

[bugzilla-daemon@kernel.org]

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

Mathias Nyman (mathias.nyman@linux.intel.com) changed:

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--- Comment #14 from Mathias Nyman (mathias.nyman@linux.intel.com) ---
Looks like it gets stuck during xhci ring expansion.

During ring expansion the xhci driver allocates memory with spinlock held using
dma_pool_zalloc(.., GFP_ATOMIC, ...)

This apparently never completes, so spinlock isn't released.
Any URBs queued for xhci after this will spin forever trying to take the lock,
lockin up that CPU.

The xhci ring expansion code looks broken, the calculation of new ring segments
needed is incorrect, may be huge.

Also I don't think we should need to expand the ring buffer in this case. There
might be some bug in how driver keeps track on free trbs.

I'll write a debugging patch that that tracks free trbs and expansion values.

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