Re: 2.6.11-rc2-mm1

[Evgeniy Polyakov <johnpol@2ka.mipt.ru>]

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On Tue, 2005-01-25 at 22:42 +0000, Christoph Hellwig wrote:
> > Zeroing can be found easily - the whole structure is NULL pointer, 
> > and will always panic if accessed(from running superio code), 
> > but redzoning is only happen on borders,
> > and can catch writes over the boards, which is rarely in this case.
> 
> As I mentioned the redzoning was a brainfar on my side.  Slab debug
> code memsets all code with an easily recognizable pattern (which 0 is _NOT_).
> 
> So this is totally useless, please don't do it - as all major subsystems
> don't do it either.

Ok, I do not insist.

> > Each superio chip is registered with superio core without any devices.
> > Each logical device is registered with superio core without any superio
> > chip.
> > 
> > Then core checks if some chip is found in some superio device, and
> > links 
> > it to appropriate device.
> > So if board has several superio chips(like soekris board) and several
> > logical devices in it, then we only have 2 superio small drivers, and
> > several 
> > logical device drivers, but not
> > number_of_superio_chips*number_of_logical_devices drivers.
> 
> That's how just about any bus driver works so far.
> 
> Now somewhere else in the thread I read the a single logical device
> might belong to multiple superio devices.  Which is kinda odd, but in
> that case it's indeed needed.
> 
> So please add a big comment explaining that properperty because it
> is extemly uncommon, and make 'ptr' in the chain structure typed
> instead of void *

Ok.

> > Yes, and it is better than removing module whose structures are in use.
> > SuperIO core is asynchronous in it's nature, one can use logical device 
> > through superio core and remove it's module on other CPU, above loop
> > will
> > wait untill all reference counters are dropped.
> 
> General rule is: increment module reference count while the hardware
> is actually in use, and let device structures be allocated by the
> bus core so drivers can be freed with them still allocated.  That's
> how the driver model and thus about every other subsystem works.

It is not general rule - network stack does not have such mechanism,
which is 
very good, I doubt each block device module increment it's module
reference
when it catch a request...
It is internal structure that has reference counter, not module itself,
and this 
structure may be in use, when module is unloaded, thus unloading must
wait, 
untill all it's structures are freed.

-- 
        Evgeniy Polyakov

Crash is better than data corruption -- Arthur Grabowski

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