Timeout problem on reads

[jorge courett]

Hi!! 

 I have a timing problem with holding register reads using an old 2.6.32 kernel with libmodbus 3.0.6 and 3.1.4. I already tested it on a 4.10 kernel and It's works fine but I can't running more than 100 msec betwen each query. Also I aready tested it on several hardware, and virtualized too. 

Fail test:

[05][03][10][00][00][05][80][8D]

Waiting for a confirmation...

Select Time was: 40.000000

<05><03>Select Time was: 0.000000

<0A>Select Time was: 0.000000

<00><00><00><00><00>Select Time was: 11.000000

<00><00><00><00><00><2A><32>

Note: "Select Time was" aditional debug messages measuring time betwen select call and trigger time. 

OK test: 

[05][03][10][00][00][05][80][8D]

Waiting for a confirmation...

<05><03><0A><00><00><00><00><00><00><00><00><00><00><2A><32>

Notice the chopped read!

I think that the problem may be come from kernel scheduling or  serial drivers.  The problem is independent from the amount of the configured timeout value.

Someone can give me any clue? 

Many thank !!

Regards 

Jorge