Re: open a file in spin_lock_irq()

[prasanna wakhare <prasannawakhare@xxxxxxxxx>]

hi,
Not know  much about yr question but share something
with you ,
what i had done was used a counter which is of type
atomic_t ,and try to simulate semaphore like situation
,where critical region check for 0 of the counter
this way interrupts remain enable as u already wrote
that,u had tried spin_lock,so how exactly to do this
i think you better know,anyway your intention is to
protect a shared list which can be done.
if this is not what you expect then plz ignore this
thanks 
Prasanna
--- Guillaume Thouvenin
<guillaume.thouvenin@xxxxxxxxxx> wrote:
> Selon Guillaume Thouvenin
> <guillaume.thouvenin@xxxxxxxxxx>:
>  
> >  I wrote a piece of kernel code that deals with
> new structure. Those
> > stucture
> > are manipulated by a driver. So, I implemented a
> classical ioctl() with a
> > switch
> > to select appropriate action to perform. One of
> this action is to remove a
> > data
> > from a list:
> 
> Oops, some parts of the mail are missing so I
> resume:
> 
> I implemented the ioctl as follow:
> 
> int my_ioctl(...) {
>     ...
>     switch(cmd) {
>         case REMOVE_AN_ITEM:
>             spin_lock_irq(&my_lock);
>             update_my_structure();
>             spin_unlock_irq(&my_lock);
>             break;
>          ....
>     }
> }
> 
> Function update_my_structure() remove an item from a
> list of items and if the
> list is empty, it dumps information about this list
> in a file. So, in this
> function I call filp_open() if list is empty. The
> problem is that you can not
> call filp_open() if you are in a spinlock because
> irq must be enable. So my
> question is how can you open a file if you are in a
> spin_lock_irq()? Can I use
> spin_lock() instead of spin_lock_irq() when doing
> some ioctl?  
> 
> I tried (peudo-code):
> 
> int update_my_structure()
> { 
>     ...
>     remove_item();
>     if (list is empty()) {
>        local_irq_enable();
>        f = filp_open();
>        f->write(info);
>        filp_close(f);
>        local_irq_disable();
>     }
>     ...
>  
> 
> But it doesn't work. It seems that it produces a
> lock and kernel freezes.
> 
> Thanks for your help
> Guillaume
> 
> --
> Kernelnewbies: Help each other learn about the Linux
> kernel.
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