David Powell wrote:
I have a question here.
I have two drivers, say A and B, that cooperate to provide a specific
funcationality. A can call a routine provided by B and passes in a
callback as a parameter so that B can use that to call into A. From
this point of view, they behavior like module. Such calls could be
issued even before the drivers create minor nodes. Yet I can only
create one-way dependency, say A depends on B.
The issues is: it's possible that A could be unloaded, which is very
possible with debug kernel, when B call into A. And the system will
panic.
Is there a way out ?
Great question.
If "B" has a routine which registers a callback, it should also have
a routine which unregisters the callback. The unregistration routine
shouldn't return successfully until the callback is removed and all
callers to the callback have returned. (It depends on the situation
whether it is more appropriate to wait for callers to drain or
immediately return EBUSY). "A" should call this unregistration
routine before it allows itself to be unloaded.
At which point to call this unregister routine ? _fini ?
Thank you
--Freeman
I'm no DDI expert, though, so there might be a more elegant way to
implement this relationship I don't know about.
Dave
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