Does FreeRTOS-Plus-TCP support cooperative scheduling?

Libraries
1

My FreeRTOS program has a TCP task which uses socket API. I want to use cooperative scheduler for the program, but my vendor-provided lwip port doesn’t work if configUSE_PREEMPTION is 0.
Does FreeRTOS-Plus-TCP support cooperative scheduling?

2

@mjs

FreeRTOS+TCP isnt well tested with cooperative scheduling.

Is there something that prevents you from using the preemptive scheduler?

3

My application has many communication tasks that use various protocols to access all kinds of data (inputs, states of business tasks, parameters). I don’t know how to properly share data among tasks in a preemptive scheduler, apart from using a global mutex in every task (which would be effectively cooperative).

4

Is your application structure such that all tasks access all the data? If not, you can divide data into groups for more granular locking instead of a global mutex. Tasks operating on the global data can make a local copy and then use that - this will shorten the critical section and you can consider using taskENTER_CRITICAL/taskEXIT_CRITICAL instead of mutex.

5

Here is my 2 cents:

Suppose you have this priority scheme:

  • Priority 3: The network interface (highest)
  • Priority 2: The TCP/IP task
  • Priority 1: Your task which uses TCP/IP

Suppose that preemption is disabled, then your task will be able to hold up the higher-priority tasks. Maybe it has to do a big FFT analysis, taking a few seconds. That would be fatal for TCP/IP operations.

So I don’t know if cooperative scheduling will work for you, for me it won’t. My lowest-priority-tasks have the freedom to sort out difficult things, without disturbing other tasks, without having to yield.

So “cooperative scheduling” is supported, but it demands that lower-priority tasks behave well, which means that they leave enough processing time for the IP-stack and other drivers.