kthread_exit(9) unexpectedness

[Lawrence Stewart]

Lawrence Stewart wrote:
> Julian Elischer wrote:
>> Lawrence Stewart wrote:
>>

[snip]

> 
>>
>>>
>>> On the other, we have the 7.x documented behaviour which is correct, 
>>> but the actual behaviour of the code (which is historically 
>>> consistent) is incorrect and at odds with the 8.x behaviour.
>>
>> in 7.x nearly everything uses kproc... so we could probably safely 
>> change it now.
> 
> We could definitely change it for all in tree cases easily enough. My 
> concern is out of tree code. This change would make any out of tree code 
> that relies on the actually implemented wakeup() mechanism potentially 
> deadlock, which is not nice. We could argue that the documented 
> behaviour is correct and that we're correcting a bug with the fix... 
> still, tis cold comfort for anyone who's working code now deadlocks.
> 
> I do like the maintenance simplicity the change would bring moving forward.
> 
> I'm still not sure the code change is the best idea. Does anyone else 
> have thoughts on the matter?
> 

[snip]

*slaps forehead*

So, it just occurred to me through my mid-morning mental haze after a 
chat with attilio@ that we should just call wakeup() on both the *proc 
_and_ *thread in 7.x and be done with it. It doesn't hurt anyone, 
maintains the current behaviour, ensures we're living up to our 
documented KPI of delivering a wakeup on the thread handle and resolves 
the compatibility issues between 7.x and 8.x in this respect - no 
potential deadlocks is good++.

I'll have a go at a patch for code + man pages shortly.

Cheers,
Lawrence