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SubjectRe: File access
Thanks I have looked at the attached file and I would really not like to 
access a file from the kernel but I cannot seem to get the user land app to
work with writing. If you consider a kernel module which, in some event,
needs to save some information in a file. The usr app is blocked in a read
with interruptible_sleep_on. When the first write occurs the module calls
wake_up_interruptible to write the data. Before the module can write the next
chunk of data it needs to stall until the user process has finished.
I can not find a method of stalling the module so it seems my only solution
is to write the file from the kernel or dump the data somewhere manually.



On Tuesday 19 Aug 2003 1:17 pm, Richard B. Johnson wrote:
> On Tue, 19 Aug 2003, Simon Haynes wrote:
> > I actually had a character interface which I use for on the fly
> > configuration. I have now implemented some code which uses a user process
> > to pass the configuration to the driver. I have however run into problems
> > trying to write files from the driver. I have tried implementing a user
> > process which performs a blocking read. The user process is blocked with
> > interruptible_sleep_on and is woken by the main part of the driver when
> > it needs to write. The problem is I then need to stall the main part of
> > the driver while the data gets written out. My problem is that this write
> > needs to happen from an interrupt handler or a timer process. I cannot
> > seem to block these with interruptible_sleep_on, the kernel crashes. I
> > guess you cannot use this in these cases ? I have also tried semaphores
> > without much success. I have looked for the howto but failed there also.
> >
> > Could you please tell me where I could find this FAQ.
> >
> > Many Thanks
> >
> > Simon.
> You may want to post this somewhere. I don't have a web-page.
> We are treated like prisoners here ;;;)) Just kidding, Thor
> (network spy).
> Cheers,
> Dick Johnson
> Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
> Note 96.31% of all statistics are fiction.
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