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SubjectRe: Module open() problems, Linux 2.4.0
"Richard B. Johnson" wrote:
>
> On Thu, 9 Nov 2000, Brian Gerst wrote:
>
> > "Richard B. Johnson" wrote:
> > >
> > > `lsmod` shows that a device is open twice when using Linux-2.4.0-test9
> > > when, in fact, it has been opened only once.
> > >
>
> > >
> > > When the module is closed, the use-count goes to zero as expected.
> > > However, a single open() causes the use-count to be 2.
> >
> > This is harmless. It is caused by a try_inc_mod_count(module) in the
> > function calling device_open(), which is the proper way for module
> > locking to be handled when not holding the BKL. You can keep the
> > MOD_INC_USE_COUNT in the device driver for compatability with 2.2.
> >
> > Brian Gerst
>
> This may be, as you say, "harmless". It is, however, a bug. The
> reporting must be correct or large complex systems can't be
> developed or maintained.
>
> I had two persons, working nearly a week, trying to find out
> what one of over 200 processes had a device open when only
> one was supposed to have it opened. --Err we have to check
> our work here. The fact that something "works" is not
> sufficient.

It is not a bug. The only values that matter are zero and non-zero. As
long as the refcounting is symmetric, it all comes out in the wash.
Remove the MOD_{INC,DEC}_USE_COUNT from your driver if it bothers you
that much and you don't care about 2.2 compatability.

--

Brian Gerst
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