Re: open() and close() from multithread application

On 08-Mar-26 12:10 PM, J. Hannken-Illjes wrote:
>> On 7. Mar 2026, at 18:59, Beesdeckar <[email protected]> wrote:
>>
>> Hello,
>>
>> I have application with three threads, second and third threads are created with pthread_create().
>> In kernel module my d_open and d_close handlers contains reference count incrementing in d_open and decrementing in d_close handler.
>> All is right in several first sequences open(), ioctl(), close() .
>> These sequences can be called from all three threads simultaneously.
>> After some time module comes to state that d_close is never reached when called close(), I checked close() in user-mode debugger and it returns always 0.
>> I am sure that d_close is not called I don't see my printf() output,
>> but I see all another d_open calls, and when checked my reference count
>> it is on every d_open incremented and never decremented.
>>
>> What to investigate to find why d_close handler is not called ?
>> I use kernel with enabled DIAGNOSTIC, DEBUG, LOCKDEBUG.
> 
> Suppose d_open() gets called on every open while d_close() only gets called on last close.
> 
> --
> J. Hannken-Illjes - [email protected]

I put this question to find how to implement reference counting in 
kernel module.
I want to return EBUSY to modunload if some user-mode app has device 
opened and calls ioctl().
Does exist some way how to force calling d_close on every close() ?
Or does exist way how to retrieve some OS internal reference count for 
kernel module ?