[Cake] Heaps of cake

[Jonathan Morton]

> On 21 May, 2016, at 01:07, Jonathan Morton <chromatix99 at gmail.com> wrote:
> 
> Please do hammer on these codepaths for all you’re worth.  It compiles and survives a smoke-test, that’s all I know so far.

Having noted a series of kernel panics in cake_drop(), I eventually traced the fault to dequeue_head(), which AFAIK hadn’t been touched since the first version (as it was lifted from fq_codel).  If it’s called on en empty subqueue, it tried to read NULL->next.

The question remains why cake_drop() would select an empty subqueue as the longest one - evidently there’s a missing heap update somewhere.  But at least now it won’t crash if that happens.

 - Jonathan Morton