Re: [PATCH] x86: introduce bootmem_state

Jeremy Fitzhardinge
2009-03-07T00:10:38Z

H. Peter Anvin wrote:
> Jeremy Fitzhardinge wrote:
>>
>> Please, no. system_state should be deprecated; its hard enough to
>> have a notion of some kind of system-wide state, but putting
>> subsystem specific substates into it just makes things worse.
>>
>
> Does it? It seems to me to have a bunch of state variables which can
> interact in $DEITY knows how many ways sounds like a bad idea.

If each state variable describes the state of a single subsystem in a
well-defined way then it is meaningful and fairly easy to understand; I
would love to have a straightforward way to query which allocator is
safe to use at a given moment.

The total number of states is always going to be subsys1 * subsys2 *
..., but folding them all into one state variable only makes sense if we
have a well-defined set of states *and* transitions between them. But
even then it implies that we have enough coupling between our subsystems
that we would even care what their aggregate state is, which is already
a bad idea. If we keep the internal workings of our subsystems as
internal details, then having private state variables is the way to go.

The real problem with system_state is that it has a few broadly-defined
values, but no real explanation of what they mean, so they end up
getting used in inappropriate ways (like the virt_addr_valid() thing I
fixed yesterday).

J