> > > > > struct usb_device->serialize will become a read-write semaphore.
> >
> > The only reason to go for an rw-semaphore is contention. If contention is
> > low, there's no point in going for the extra overhead of such a lock.
>
> No, there can be other reasons too. For example, suppose one routine that
> gets a read lock calls another that does the same thing. That works well
> with rw-semaphores but not with regular ones. That's not contention, it's
> something else (poor design perhaps -- but Duncan has his reasons).
NO ! You are running to Mount Doom and dragging along the horses.
rw-semaphores are fair. If you have this sequence:
TASK A TASK B
down_read()
down_write()
down_read() --> DEADLOCK
You must not do this. Debugging such a thing will drive programmers
to madness in incredible numbers.
Regards
Oliver
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