Mailinglist Archive: opensuse (2162 mails)

[Per Jessen <per@xxxxxxxxxxxx>]

Roger Oberholtzer wrote:

> I have a C application that access a GPS receiver over a serial port.
> Over the years, using Linux (SUSE variants back a long way), I have
> experienced a problem that has never gone away. Although it appears on
> the surface to be a programming question, I think it is really a
> kernel / serial port issue. As I see it in openSUSE, I am starting my
> quest for a solution here.
>
> The problem is that, after a variable amount of time, reads of the
> serial port stop blocking (as the port has been configured to do) when
> there is no data, and start returning immediately with errno set to
> EAGAIN. This can happen after 5 minutes of running the app, or after 5
> hours. There is no discernible pattern.
>
> The code in the application is childishly simple:
>
> 1. Open the serial port in the C application, controlling it via
> termio().
> 2. Do a blocking read on the port.
> 3. When data arrived, write it to a disk file.
> 4. Go to step 2.
>
> Anyone else using the serial port to record data over long periods of
> time?

Hi Roger

we have two applications that both read/write to/from a serial port. 
One application reads temperature measurements and writes commands, the
other is a standard NTP reading a DCF77 signal from the serial port. 
The first application is on SUSE 9.0, the second is on openSUSE 10.2.
They've both been running for a couple of years, and neither have ever
showed any problems.
Your pseudo-code looks pretty much like mine (for the temp controller),
except I write a command to the serial port before I read the
temperature.


/Per Jessen, Zürich

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