Messages in this thread |  | | Date | Thu, 09 Nov 2000 15:27:16 -0500 | From | Jeff Garzik <> | Subject | Re: Module open() problems, Linux 2.4.0 |
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"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.
There is NO guarantee that module use count == device open count. Never has been, AFAIK. It just happens to work out that way on a lot of pre-2.4 code.
The kernel is free to bump the module reference count up and down as it pleases. For example, if a driver creates a kernel thread, that will increase its module usage count by one, for the duration of the kernel thread's lifetime.
The only rule is that you cannot unload a module until its use count it zero.
Jeff
-- Jeff Garzik | Building 1024 | Would you like a Twinkie? MandrakeSoft | - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/
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