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CMSIS-RTOS2
Version 2.0.0
Real-Time Operating System: API and RTX Reference Implementation
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The CMSIS-RTOS RTX provides several parameters to configure the Thread Management functions.
The CMSIS-RTOS RTX kernel uses a separate stack space for each thread and provides two methods for defining the stack requirements:
osThreadAttr_t is a parameter of the function osThreadNew.
RTX5 implements a software stack overflow checking that traps stack overruns. Stack is used for return addresses and automatic variables and extensive usage or incorrect stack configuration may cause a stack overflow. Software stack overflow checking is controlled with the define OS_STACK_CHECK
.
If a stack overflow is detected, the function os_Error with error code os_ErrorStackUnderflow is called. By default, this function is implemented as endless loop and will practically stop code execution.
RTX5 initializes thread stack with watermark pattern (0xCC) when a thread is created. This allows the debugger to determine maximum stack usage for each thread. It is typically used during development but removed from the final application. Stack usage watermark is controlled with the define OS_STACK_WATERMARK
.
Enabling this option significantly increases the execution time of osThreadNew (depends on thread stack size).
RTX5 allows to execute threads in unprivileged or privileged processor mode. The processor mode is controlled with the define OS_PRIVILEGE_MODE
.
In unprivileged processor mode, the software:
Thread Configuration Options
Option | #define | Description |
---|---|---|
Object specific Memory allocation | OS_THREAD_OBJ_MEM | Enables object specific memory allocation. See Object-specific Memory Pools. |
Number of user Threads (total) | OS_THREAD_NUM | Defines maximum number of user threads that can be active at the same time. Applies to user threads with system provided memory for control blocks. Default value is 1. Value range is [1-1000]. |
Number of user Threads with user-provided Stack size | OS_THREAD_USER_STACK_NUM | Defines maximum number of user threads with user-provided stack size. Default value is 0. Value range is [0-1000]. |
Total Stack size [bytes] for user Threads with user-provided Stack size | OS_THREAD_USER_STACK_SIZE | Defines the combined stack size for user threads with user-provided stack size. Default value is 0. Value range is [0-1073741824] Bytes, in multiples of 8. |
Default Thread Stack size [bytes] | OS_STACK_SIZE | Defines stack size for threads with zero stack size specified. Default value is 200. Value range is [96-1073741824] Bytes, in multiples of 8. |
Idle Thread Stack size [bytes] | OS_IDLE_THREAD_STACK_SIZE | Defines stack size for Idle thread. Default value is 200. Value range is [72-1073741824] bytes, in multiples of 8. |
Stack overrun checking | OS_STACK_CHECK | Enable stack overrun checks at thread switch. |
Stack usage watermark | OS_STACK_WATERMARK | Initialize thread stack with watermark pattern for analyzing stack usage. Enabling this option increases significantly the execution time of thread creation. |
Processor mode for Thread execution | OS_PRIVILEGE_MODE | Controls the processor mode. Default value is Privileged mode. Value range is [0=Unprivileged; 1=Privileged] mode. |