Why does datasocket write allow preemption?

[knicewar]

I have a RT high priority 1 kHz timed event loop that occasionally needs to send something to a shared variable via a data socket write.  I'm using a timeout of 0 for the DS write which should be fire-and-forget.  But what I'm seeing is that this allows a lower-priority thread to preempt the high priority thread for over 15 ms.  Classic priority inversion.  If I disable the DS write, things run smoothly.  I would have expected that the DS write was safe to call from a high-priority thread.  Is it taking a system-wide mutex to talk on the socket?  The DS it's writing to is not used in any other threads on the target, so I'm perplexed by this.  Should I not be using DS from a high-priority high-frequency thread?  Should I instead use a RT FIFO to talk to a DS?

Thanks,

Keith.

[knicewar]

I'm not even sure how I'd use an RT FIFO.  I have a DS reference and the value (boolean or timestamp).  The FIFO only stores arrays of simple types.  Any ideas?  Do I create a cluster, flatten it to a string, then convert the string to a byte array?  That seems pretty round-about ...

Keith.

[Kameralina]

Hello Keith,

> Should I not be using DS from a high-priority high-frequency thread?

Network communication should not be done from the time-critical or highest priority threads.

Could you post the portion of the code that you are speaking of, so that we can better visualize what you are describing?

Here is a comparison of some of the different communication methods.  Since you are speaking of priorities, are you using Real-Time?

Real-Time VI to Host VI Communication Methods

http://digital.ni.com/public.nsf/allkb/48D244EC86971D3986256BD4005CCC28?OpenDocument