Re: [PATCH] mce: fix warning messages about static struct mce_device

[Ingo Molnar]

* Kay Sievers <kay.sievers@xxxxxxxx> wrote:

> > There's nothing special about the driver model code in this 
> > respect. The same restriction applies wherever object 
> > lifetimes are controlled by reference counting.
> 
> Right. But it might not be obvious what 's the background 
> here:
> 
> An allocated device object(memory) usually represents an 
> actual device(hardware). The object can have N users. Every of 
> the users is required to take a reference to the object, which 
> pins the object's memory as long as any of the N users might 
> need to access it.
> 
> In a hotplug world, we deal with device-removal.  On 
> disconnect, we usually just orphan the object, we remove it 
> from visibility, disconnect the device <-> object relation.
> 
> All of the N users with a reference can still access the 
> memory, they just do not talk to a real device anymore. The 
> invalidated/orphaned state is communicated otherwise by locks 
> and flags in the device object. Only after all of the N users 
> left the object alone, the memory of the orphan if free'd.

But this is not what happened here - it's a special piece of 
fundamental hardware that doesnt hot-plug separately from the 
CPU and that has just a single "user".

So i'm curious, why wasn't the memset() enough? It should have 
resolved the bug AFAICS.

Thanks,

	Ingo
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