Re: opening linux char device file in user thread.

From: P.Manohar
Date: Sat Aug 13 2005 - 05:07:41 EST


thanks for help, it is working now, I opened the char file before the thread starts.

On Thu, 4 Aug 2005, Bhanu Kalyan Chetlapalli wrote:

On 8/4/05, P.Manohar <pmanohar@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:

hai,

I have written a daemon which is running in user space, will send some
data periodically to kernel space. This I have done with the help of a
device file.

It is working, but I want to apply threads mechanism in that daemon. But
when I split that daemon functionality into a thread and a original
process. I am unable to
open the device file. This is happening in both places(either in thread or
original process).

Try opening the device, get the FD and THEN spawn the thread. this
will help, as the device is opened only once as far as the driver is
concerned. The presence of usage from the thread is felt only in the
reference count of the fd (which should be transparent to user space
and the device driver). Race conditions are assumed to be taken care
of in the kernel module though.

The other way is to open device, write data, close device every time u
write something. This is beneficial if the time between the writes is
seperated by more than a minute. There will be no races etc to take
care of.

The device is opening when threading is not there.

Can anybody suggest me?

Regards,
P.Manohar.


Bhanu.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/



--
The difference between Theory and Practice is more so in Practice than
in Theory.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/