Re: Unloading drivers, start-up, shut-down and a rewrite (a problem)

[Stamatis Mitrofanis <ewstam@softhome.net>]

>
>
>More details please.  Why do you need to externally adjust a module's
>use count?  All other modules handle their use counts internally, what
>is different about hotplug?
>
>I will do the patch to kernel/module.c, once I understand exactly what
>the requirements are.
>
It's when you have many hotpluggable devices of the same type (handled 
by the same driver). Managing a reference (device) count for each driver 
from the hotpug scripts is necessary for unloading the driver _only_ 
after the last such device is unplugged.

It might be a bad idea to play with the modules' real reference counts 
though, but there must be at least some form of mutual exclusion for 
accessing this driver-specific device count. Therefore, it was wrong for 
me to try to implement this device count by making the scripts 
read/write"*.ref" files in the hotplug directory (possible race 
condition which would mess up the count).

If it should be implemented in the kernel then the functionality should 
be exposed through modprobe. I'm sorry, but I have no idea about the 
actual details of (un)loading modules so you'll have to do everything 
behind modprobe.

The requirement is just that modprobe gets a new command-line paremeter 
which, when given in a call to load/unload a module, will also 
increment/decrement the module's reference count. I.e. if  the parameter 
is "--ref" and the module ABC is not loaded, then the following should 
result in module ABC being in memory with a reference count of 1:
# modprobe --ref ABC
# modprobe --ref ABC
# modprobe --ref -r ABC
The first command will load the module and set its reference count to 1. 
The second command will increment the ABC's reference count to 2 and the 
third should decrement the reference count to 1 without, of course, 
unloading the module.



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