Re: [PATCH 5/5 V2] kvm tools: Initialize and use VESA and VNC

[Paolo Bonzini <pbonzini@redhat.com>]

On 05/24/2011 10:50 AM, Ingo Molnar wrote:
> Yeah, that would certainly work for simple things but there's several reasons
> why explicit control over initcalls is preferred in a tool like tools/kvm/ over
> __attribute__((constructor)):

Some advantages you mention are real indeed, but they are general; 
there's no reason why they apply only to tools/kvm.  You can achieve the 
same by doing only minimal work (registering your 
subsystems/devices/whatever in a linked list) in the constructors.  Then 
you iterate on the list and call function pointers.

I know portability is not relevant to tools/kvm/, but using unportable 
tricks for the sake of using them is a direct way to NIH.  But oh well 
all of tools/kvm/ is NIH after all. :)

>   - The kernel has several classes of initcalls with different call priority,
>     i'm not aware of an equivalent __attribute__((constructor)) capability.
>     We could also do more sophisticated layers of initcalls or an explicit
>     initcall dependency tree, should the need arise.

Constructors and destructors can have a priority (low runs first for 
constructors, low runs last for destructors).

Paolo