RTOS/TM4C1294NCPDT: Event_pend and Semaphore_pend: asserted at "Assert_isTrue((BIOS_getThreadType() == BIOS_ThreadType_Task)"

Part Number:TM4C1294NCPDT

Tool/software:TI-RTOS

tm4c1294ncpdt
CCS6.1.3
tirtos_tivac_2_10_01_38
compiler: TI V5.1.11
XDC: 3.30.4.52

I have a board running on field. Occassionally the board resets. I added an errorHook to capture the error data, and found it asserted at line 199 of "Event_pend" and line 202 of "Event_pend". Both of them are checking if(Please visit the site to view this file) it is called by a thread, not HWI/SWI/main.
My code does call both function, but all in tasks. So my questions are:
1. Does this mean other code such as BIOS or drivers calls these function in HWI/SWI? But I searched "Event_pend" in folder "C:\ti\tirtos_tivac_2_10_01_38\packages\ti" and "C:\ti\tirtos_tivac_2_10_01_38\products", and found there seems no calling, except in an example and uia.
2. Is there a way to know who calls a funtion by checking linker output?

The attached are file "event.c", "semaphre.c" and .cfg.

Thanks