On Thursday 17 March 2011, [email protected] wrote:
> >This is not very different from opening the file descriptor in
> >multiple processes, which you prevent using your logic.
>
> but in the case when two independent applications try to open
> my device I can't let the second to access. They obviously won't
> synch the access.
My point was that you don't need to worry.
> >You can of course argue that you try your best to prevent the
> >race. Traditionally, e.g. on serial ports and the like, we
> >don't do this but instead rely on user space synchronizing the
> >access. What you have to make sure of course is that multiple
> >threads calling read on the same file can never bring the
> >kernel driver into an invalid state.
>
> I assume, if an application shares the file pointer deliberately
> it have to sync the access. In other cases, the driver needs to
> secure it.
As I said, it's not important if you do it and it certainly doesn't
cause harm to prevent multiple open. It's just that generally
we don't care too much about this problem.
Arnd
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