[lwip-devel] [task #16181] Priority desynchronization between LwIP and FreeRTOS

[Jonathan D]

URL:
  <https://savannah.nongnu.org/task/?16181>

                 Summary: Priority desynchronization between LwIP and FreeRTOS
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: jona
            Submitted on: Thu 05 May 2022 03:08:10 PM UTC
                Category: Contrib
         Should Start On: Thu 05 May 2022 12:00:00 AM UTC
   Should be Finished on: Thu 05 May 2022 12:00:00 AM UTC
                Priority: 4
                  Status: None
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
                  Effort: 0.00

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Details:

In LwIP, priorities for tasks span from -3 to +3.
In FreeRTOS, priorities span from 0 to 6.

Here is a patch to resynchronize both scales:

---
diff --git a/ports/freertos/sys_arch.c b/ports/freertos/sys_arch.c
index 84bd463..7d40f83 100644
--- a/ports/freertos/sys_arch.c
+++ b/ports/freertos/sys_arch.c
@@ -477,7 +477,7 @@ sys_thread_new(const char *name, lwip_thread_fn thread,
void *arg, int stacksize
 
   /* lwIP's lwip_thread_fn matches FreeRTOS' TaskFunction_t, so we can pass
the
      thread function without adaption here. */
-  ret = xTaskCreate(thread, name, (configSTACK_DEPTH_TYPE)rtos_stacksize,
arg, prio, &rtos_task);
+  ret = xTaskCreate(thread, name, (configSTACK_DEPTH_TYPE)rtos_stacksize,
arg, makeFreeRtosPriority(prio), &rtos_task);
   LWIP_ASSERT("task creation failed", ret == pdTRUE);
 
   lwip_thread.thread_handle = rtos_task;
---

With:
---
/* Convert from CMSIS type osPriority to FreeRTOS priority number */
unsigned portBASE_TYPE makeFreeRtosPriority (osPriority priority)
{
  unsigned portBASE_TYPE fpriority = tskIDLE_PRIORITY;
  
  if (priority != osPriorityError) {
    fpriority += (priority - osPriorityIdle);
  }
  
  return fpriority;
}
---





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