Define, create, and control thread functions. More...

Data Structures
struct	osThreadAttr_t
	Attributes structure for thread. More...

Macros
#define	osThreadJoinable 0x00000001U
	Thread created in joinable mode. More...

#define	osThreadDetached 0x00000000U
	Thread created in detached mode (default) More...

#define	osThreadUnprivileged 0x00000002U
	Thread runs in unprivileged mode. More...

#define	osThreadPrivileged 0x00000004U
	Thread runs in privileged mode. More...

#define	osThreadZone(n)
	MPU zone value in attribute bit field format. More...

Typedefs
typedef void(*	osThreadFunc_t )(void *argument)
	Entry point of a thread. More...

typedef void *	osThreadId_t

Enumerations
enum	osThreadState_t { osThreadInactive = 0, osThreadReady = 1, osThreadRunning = 2, osThreadBlocked = 3, osThreadTerminated = 4, osThreadError = -1, osThreadReserved = 0x7FFFFFFF }
	Thread state. More...

enum	osPriority_t { osPriorityNone = 0, osPriorityIdle = 1, osPriorityLow = 8, osPriorityLow1 = 8+1, osPriorityLow2 = 8+2, osPriorityLow3 = 8+3, osPriorityLow4 = 8+4, osPriorityLow5 = 8+5, osPriorityLow6 = 8+6, osPriorityLow7 = 8+7, osPriorityBelowNormal = 16, osPriorityBelowNormal1 = 16+1, osPriorityBelowNormal2 = 16+2, osPriorityBelowNormal3 = 16+3, osPriorityBelowNormal4 = 16+4, osPriorityBelowNormal5 = 16+5, osPriorityBelowNormal6 = 16+6, osPriorityBelowNormal7 = 16+7, osPriorityNormal = 24, osPriorityNormal1 = 24+1, osPriorityNormal2 = 24+2, osPriorityNormal3 = 24+3, osPriorityNormal4 = 24+4, osPriorityNormal5 = 24+5, osPriorityNormal6 = 24+6, osPriorityNormal7 = 24+7, osPriorityAboveNormal = 32, osPriorityAboveNormal1 = 32+1, osPriorityAboveNormal2 = 32+2, osPriorityAboveNormal3 = 32+3, osPriorityAboveNormal4 = 32+4, osPriorityAboveNormal5 = 32+5, osPriorityAboveNormal6 = 32+6, osPriorityAboveNormal7 = 32+7, osPriorityHigh = 40, osPriorityHigh1 = 40+1, osPriorityHigh2 = 40+2, osPriorityHigh3 = 40+3, osPriorityHigh4 = 40+4, osPriorityHigh5 = 40+5, osPriorityHigh6 = 40+6, osPriorityHigh7 = 40+7, osPriorityRealtime = 48, osPriorityRealtime1 = 48+1, osPriorityRealtime2 = 48+2, osPriorityRealtime3 = 48+3, osPriorityRealtime4 = 48+4, osPriorityRealtime5 = 48+5, osPriorityRealtime6 = 48+6, osPriorityRealtime7 = 48+7, osPriorityISR = 56, osPriorityError = -1, osPriorityReserved = 0x7FFFFFFF }
	Priority values. More...

Functions
osThreadId_t	osThreadNew (osThreadFunc_t func, void argument, const osThreadAttr_t attr)
	Create a thread and add it to Active Threads. More...

const char *	osThreadGetName (osThreadId_t thread_id)
	Get name of a thread. More...

uint32_t	osThreadGetClass (osThreadId_t thread_id)
	Get safety class of a thread. More...

uint32_t	osThreadGetZone (osThreadId_t thread_id)
	Get MPU protected zone of a thread. More...

osThreadId_t	osThreadGetId (void)
	Return the thread ID of the current running thread. More...

osThreadState_t	osThreadGetState (osThreadId_t thread_id)
	Get current thread state of a thread. More...

osStatus_t	osThreadSetPriority (osThreadId_t thread_id, osPriority_t priority)
	Change priority of a thread. More...

osPriority_t	osThreadGetPriority (osThreadId_t thread_id)
	Get current priority of a thread. More...

osStatus_t	osThreadYield (void)
	Pass control to next thread that is in state READY. More...

osStatus_t	osThreadSuspend (osThreadId_t thread_id)
	Suspend execution of a thread. More...

osStatus_t	osThreadResume (osThreadId_t thread_id)
	Resume execution of a thread. More...

osStatus_t	osThreadDetach (osThreadId_t thread_id)
	Detach a thread (thread storage can be reclaimed when thread terminates). More...

osStatus_t	osThreadJoin (osThreadId_t thread_id)
	Wait for specified thread to terminate. More...

__NO_RETURN void	osThreadExit (void)
	Terminate execution of current running thread. More...

osStatus_t	osThreadTerminate (osThreadId_t thread_id)
	Terminate execution of a thread. More...

uint32_t	osThreadGetStackSize (osThreadId_t thread_id)
	Get stack size of a thread. More...

uint32_t	osThreadGetStackSpace (osThreadId_t thread_id)
	Get available stack space of a thread based on stack watermark recording during execution. More...

uint32_t	osThreadGetCount (void)
	Get number of active threads. More...

uint32_t	osThreadEnumerate (osThreadId_t *thread_array, uint32_t array_items)
	Enumerate active threads. More...

osStatus_t	osThreadFeedWatchdog (uint32_t ticks)
	Feed watchdog of the current running thread. More...

osStatus_t	osThreadProtectPrivileged (void)
	Protect creation of privileged threads. More...

osStatus_t	osThreadSuspendClass (uint32_t safety_class, uint32_t mode)
	Suspend execution of threads for specified safety classes. More...

osStatus_t	osThreadResumeClass (uint32_t safety_class, uint32_t mode)
	Resume execution of threads for specified safety classes. More...

osStatus_t	osThreadTerminateZone (uint32_t zone)
	Terminate execution of threads assigned to a specified MPU protected zone. More...

uint32_t	osWatchdogAlarm_Handler (osThreadId_t thread_id)
	Handler for expired thread watchdogs. More...

void	osZoneSetup_Callback (uint32_t zone)
	Setup MPU protected zone (called when zone changes). More...

Description

The Thread Management function group allows defining, creating, and controlling thread functions in the system.

Note: Thread management functions cannot be called from Interrupt Service Routines.

Thread states

Threads can be in the following states:

RUNNING: The thread that is currently running is in the RUNNING state. Only one thread at a time can be in this state.
READY: Threads which are ready to run are in the READY state. Once the RUNNING thread has terminated, or is BLOCKED, the next READY thread with the highest priority becomes the RUNNING thread.
BLOCKED: Threads that are blocked either delayed, waiting for an event to occur or suspended are in the BLOCKED state.
TERMINATED: When osThreadTerminate is called, threads are TERMINATED with resources not yet released (applies to joinable threads).
INACTIVE: Threads that are not created or have been terminated with all resources released are in the INACTIVE state.

Thread State and State Transitions

A CMSIS-RTOS assumes that threads are scheduled as shown in the figure Thread State and State Transitions. The thread states change as follows:

A thread is created using the function osThreadNew. This puts the thread into the READY or RUNNING state (depending on the thread priority).
CMSIS-RTOS is preemptive. The active thread with the highest priority becomes the RUNNING thread provided it does not wait for any event. The initial priority of a thread is defined with the osThreadAttr_t but may be changed during execution using the function osThreadSetPriority.
The RUNNING thread transfers into the BLOCKED state when it is delayed, waiting for an event or suspended.
Active threads can be terminated any time using the function osThreadTerminate. Threads can terminate also by just returning from the thread function. Threads that are terminated are in the INACTIVE state and typically do not consume any dynamic memory resources.

Note: Refer to Thread Configuration for RTX5 configuration options.

Thread Examples

The following examples show various scenarios to create threads:

Example 1 - Create a simple thread

Create a thread out of the function thread1 using all default values for thread attributes and memory from the Global Memory Pool.

__NO_RETURN void thread1 (void *argument) {
  // ...
  for (;;) {}
}
 
int main (void) {
  osKernelInitialize();
  ;
  osThreadNew(thread1, NULL, NULL);     // Create thread with default settings
  ;
  osKernelStart(); 
}

Example 2 - Create thread with stack non-default stack size

Similar to the simple thread all attributes are default. The stack is dynamically allocated from the Global Memory Pool

osThreadAttr_t::stack_size is used to pass the stack size in Bytes to osThreadNew.

__NO_RETURN void thread1 (void *argument) {
  // ...
  for (;;) {}
}
 
const osThreadAttr_t thread1_attr = {
  .stack_size = 1024                            // Create the thread stack with a size of 1024 bytes
};
 
int main (void) {
  ;  
  osThreadNew(thread1, NULL, &thread1_attr);    // Create thread with custom sized stack memory
  ;
}

Example 3 - Create thread with statically allocated stack

Similar to the simple thread all attributes are default. The stack is statically allocated using the uint64_t array thread1_stk_1. This allocates 64*8 Bytes (=512 Bytes) with an alignment of 8 Bytes (mandatory for Cortex-M stack memory).

osThreadAttr_t::stack_mem holds a pointer to the stacks lowest address.

osThreadAttr_t::stack_size is used to pass the stack size in Bytes to osThreadNew.

__NO_RETURN void thread1 (void *argument) {
  // ...
  for (;;) {}
}
 
static uint64_t thread1_stk_1[64];
 
const osThreadAttr_t thread1_attr = {
  .stack_mem  = &thread1_stk_1[0],
  .stack_size = sizeof(thread1_stk_1)
};
 
int main (void) {
  ;  
  osThreadNew(thread1, NULL, &thread1_attr);    // Create thread with statically allocated stack memory
  ;
}

Example 4 - Thread with statically allocated task control block

Typically this method is chosen together with a statically allocated stack as shown in Example 2.

#include "cmsis_os2.h"
 
//include rtx_os.h for types of RTX objects
#include "rtx_os.h"
__NO_RETURN void thread1 (void *argument) {
  // ...
  for (;;) {}
}
 
static osRtxThread_t thread1_tcb;
 
const osThreadAttr_t thread1_attr = {
  .cb_mem  = &thread1_tcb,
  .cb_size = sizeof(thread1_tcb),
};
 
int main (void) {
  ;
  osThreadNew(thread1, NULL, &thread1_attr);    // Create thread with custom tcb memory
  ;
}

Example 5 - Create thread with a different priority

The default priority of RTX is osPriorityNormal. Often you want to run a task with a higher or lower priority. Using the osThreadAttr_t control structure you can set any initial priority required.

__NO_RETURN void thread1 (void *argument) {
  // ...
  for (;;) {}
}
 
const osThreadAttr_t thread1_attr = {
  .priority = osPriorityHigh                    //Set initial thread priority to high   
};
 
int main (void) {
  ;
  osThreadNew(thread1, NULL, &thread1_attr);
  ;
}

Example 6 - Joinable threads

In this example a master thread creates four threads with the osThreadJoinable attribute. These will do some work and return using the osThreadExit call after finished. osThreadJoin is used to synchronize the thread termination.

__NO_RETURN void worker (void *argument) {
  ; // work a lot on data[] 
  osDelay(1000U);
  osThreadExit();
}
 
__NO_RETURN void thread1 (void *argument) {
  osThreadAttr_t worker_attr;
  osThreadId_t worker_ids[4];
  uint8_t data[4][10];
  memset(&worker_attr, 0, sizeof(worker_attr));
  worker_attr.attr_bits = osThreadJoinable;
 
  worker_ids[0] = osThreadNew(worker, &data[0][0], &worker_attr);
  worker_ids[1] = osThreadNew(worker, &data[1][0], &worker_attr);
  worker_ids[2] = osThreadNew(worker, &data[2][0], &worker_attr);
  worker_ids[3] = osThreadNew(worker, &data[3][0], &worker_attr);
 
  osThreadJoin(worker_ids[0]);
  osThreadJoin(worker_ids[1]);
  osThreadJoin(worker_ids[2]);
  osThreadJoin(worker_ids[3]);
 
  osThreadExit(); 
}

Data Structure Documentation

struct osThreadAttr_t

Specifies the following attributes for the osThreadNew function.

Data Fields
const char *	name	name of the thread Pointer to a constant string with a human readable name (displayed during debugging) of the thread object. Default: NULL no name specified (debugger may display function name instead).
uint32_t	attr_bits	attribute bits The following bit masks can be used to set options: osThreadDetached : create thread in a detached mode (default). osThreadJoinable : create thread in joinable mode. osThreadUnprivileged : create thread to execute in unprivileged mode. osThreadPrivileged : create thread to execute in privileged mode. osThreadZone (m) : create thread assigned to MPU zone m. osSafetyClass (n) : create thread with safety class n assigned to it. Default: 0 no options set. Safety class and MPU Zone are inherited from running thread. Thread privilege mode is set based on configuration Processor Mode for Thread Execution.
void *	cb_mem	memory for control block Pointer to a memory for the thread control block object. Refer to Static Object Memory for more information. Default: NULL to use Automatic Dynamic Allocation for the thread control block.
uint32_t	cb_size	size of provided memory for control block The size (in bytes) of memory block passed with cb_mem. For RTX, the minimum value is defined with osRtxThreadCbSize (higher values are permitted). Default: 0 as the default is no memory provided with cb_mem.
void *	stack_mem	memory for stack Pointer to a memory location for the thread stack (64-bit aligned). Default: NULL to allocate stack from a fixed-size memory pool using Thread Stack Management.
uint32_t	stack_size	size of stack The size (in bytes) of the stack specified by stack_mem. Default: 0 as the default is no memory provided with stack_mem.
osPriority_t	priority	initial thread priority (default: osPriorityNormal) Specifies the initial thread priority with a value from osPriority_t. Default: osPriorityNormal.
TZ_ModuleId_t	tz_module	TrustZone module identifier. TrustZone Thread Context Management Identifier to allocate context memory for threads. The RTOS kernel that runs in non-secure state calls the interface functions defined by the header file TZ_context.h. Can safely be set to zero for threads not using secure calls at all. See TrustZone RTOS Context Management. Default: 0 not thread context specified.
uint32_t	reserved	reserved (must be 0) Reserved for future use.

Macro Definition Documentation

#define osThreadJoinable 0x00000001U

Bitmask for a thread that can be joined. Intended for use in attr_bits of osThreadAttr_t type argument for osThreadNew function.

A thread in this state can be joined using osThreadJoin.

#define osThreadDetached 0x00000000U

Bitmask for a thread that cannot be joined. Intended for use in attr_bits of osThreadAttr_t type argument for osThreadNew function.

A thread in this state cannot be joined using osThreadJoin.

#define osThreadUnprivileged 0x00000002U

Bitmask for a thread that runs in unprivileged mode. Intended for use in attr_bits of osThreadAttr_t type argument for osThreadNew function.

In unprivileged processor mode, a thread:

has limited access to the MSR and MRS instructions, and cannot use the CPS instruction.
cannot access the system timer, NVIC, or system control block.
might have restricted access to memory or peripherals.

Note: Ignored on processors that only run in privileged mode.

Refer to the target processor User's Guide for details.

#define osThreadPrivileged 0x00000004U

Bitmask for a thread that runs in privileged mode. Intended for use in attr_bits of osThreadAttr_t type argument for osThreadNew function.

In privileged processor mode, the application software can use all the instructions and has access to all resources.

#define osThreadZone ( n )

MPU protected zone.

Parameters

n	MPU Protected Zone value.

The preprocessor macro osThreadZone constructs attribute bitmask with MPU zone bits set to n.

Code Example:

/* ThreadB thread attributes */
const osThreadAttr_t thread_B_attr = {
  .name      = "ThreadB",       // human readable thread name
  .attr_bits = osThreadZone(3U) // assign thread to MPU zone 3
};

Typedef Documentation

void(* osThreadFunc_t)(void *argument)

Entry function for threads. Setting up a new thread (osThreadNew) will start execution with a call into this entry function. The optional argument can be used to hand over arbitrary user data to the thread, i.e. to identify the thread or for runtime parameters.

Parameters

[in] argument Arbitrary user data set on osThreadNew.

osThreadId_t

Thread ID identifies the thread.

Returned by:

Enumeration Type Documentation

enum osThreadState_t

State of a thread as retrieved by osThreadGetState. In case osThreadGetState fails or if it is called from an ISR, it will return osThreadError, otherwise it returns the thread state.

Enumerator
osThreadInactive	Inactive. The thread is created but not actively used, or has been terminated (returned for static control block allocation, when memory pools are used osThreadError is returned as the control block is no longer valid)
osThreadReady	Ready. The thread is ready for execution but not currently running.
osThreadRunning	Running. The thread is currently running.
osThreadBlocked	Blocked. The thread is currently blocked (delayed, waiting for an event or suspended).
osThreadTerminated	Terminated. The thread is terminated and all its resources are not yet freed (applies to joinable threads).
osThreadError	Error. The thread does not exist (has raised an error condition) and cannot be scheduled.
osThreadReserved	Prevents enum down-size compiler optimization.

enum osPriority_t

The osPriority_t value specifies the priority for a thread. The default thread priority should be osPriorityNormal. If an active thread becomes ready that has a higher priority than the currently running thread then a thread switch occurs immediately. The system continues executing the thread with the higher priority.

To prevent from a priority inversion, a CMSIS-RTOS compliant OS may optionally implement a priority inheritance method. A priority inversion occurs when a high priority thread is waiting for a resource or event that is controlled by a thread with a lower priority. Thus causing the high priority thread potentially being blocked forever by another thread with lower priority. To come over this issue the low priority thread controlling the resource should be treated as having the higher priority until it releases the resource.

Note: Priority inheritance only applies to mutexes.

Enumerator
osPriorityNone	No priority (not initialized).
osPriorityIdle	Reserved for Idle thread. This lowest priority should not be used for any other thread.
osPriorityLow	Priority: low.
osPriorityLow1	Priority: low + 1.
osPriorityLow2	Priority: low + 2.
osPriorityLow3	Priority: low + 3.
osPriorityLow4	Priority: low + 4.
osPriorityLow5	Priority: low + 5.
osPriorityLow6	Priority: low + 6.
osPriorityLow7	Priority: low + 7.
osPriorityBelowNormal	Priority: below normal.
osPriorityBelowNormal1	Priority: below normal + 1.
osPriorityBelowNormal2	Priority: below normal + 2.
osPriorityBelowNormal3	Priority: below normal + 3.
osPriorityBelowNormal4	Priority: below normal + 4.
osPriorityBelowNormal5	Priority: below normal + 5.
osPriorityBelowNormal6	Priority: below normal + 6.
osPriorityBelowNormal7	Priority: below normal + 7.
osPriorityNormal	Priority: normal.
osPriorityNormal1	Priority: normal + 1.
osPriorityNormal2	Priority: normal + 2.
osPriorityNormal3	Priority: normal + 3.
osPriorityNormal4	Priority: normal + 4.
osPriorityNormal5	Priority: normal + 5.
osPriorityNormal6	Priority: normal + 6.
osPriorityNormal7	Priority: normal + 7.
osPriorityAboveNormal	Priority: above normal.
osPriorityAboveNormal1	Priority: above normal + 1.
osPriorityAboveNormal2	Priority: above normal + 2.
osPriorityAboveNormal3	Priority: above normal + 3.
osPriorityAboveNormal4	Priority: above normal + 4.
osPriorityAboveNormal5	Priority: above normal + 5.
osPriorityAboveNormal6	Priority: above normal + 6.
osPriorityAboveNormal7	Priority: above normal + 7.
osPriorityHigh	Priority: high.
osPriorityHigh1	Priority: high + 1.
osPriorityHigh2	Priority: high + 2.
osPriorityHigh3	Priority: high + 3.
osPriorityHigh4	Priority: high + 4.
osPriorityHigh5	Priority: high + 5.
osPriorityHigh6	Priority: high + 6.
osPriorityHigh7	Priority: high + 7.
osPriorityRealtime	Priority: realtime.
osPriorityRealtime1	Priority: realtime + 1.
osPriorityRealtime2	Priority: realtime + 2.
osPriorityRealtime3	Priority: realtime + 3.
osPriorityRealtime4	Priority: realtime + 4.
osPriorityRealtime5	Priority: realtime + 5.
osPriorityRealtime6	Priority: realtime + 6.
osPriorityRealtime7	Priority: realtime + 7.
osPriorityISR	Reserved for ISR deferred thread. This highest priority might be used by the RTOS implementation but must not be used for any user thread.
osPriorityError	System cannot determine priority or illegal priority.
osPriorityReserved	Prevents enum down-size compiler optimization.

Function Documentation

osThreadId_t osThreadNew	(	osThreadFunc_t	func,
		void *	argument,
		const osThreadAttr_t *	attr
	)

Parameters

[in]	func	thread function.
[in]	argument	pointer that is passed to the thread function as start argument.
[in]	attr	thread attributes; NULL: default values.

Returns: thread ID for reference by other functions or NULL in case of error.

The function osThreadNew starts a thread function by adding it to the list of active threads and sets it to state READY. Arguments for the thread function are passed using the parameter pointer *argument. When the priority of the created thread function is higher than the current RUNNING thread, the created thread function starts instantly and becomes the new RUNNING thread. Thread attributes are defined with the parameter pointer attr. Attributes include settings for thread priority, stack size, or memory allocation.

The function can be safely called before the RTOS is started (call to osKernelStart), but not before it is initialized (call to osKernelInitialize).

The function osThreadNew returns the pointer to the thread object identifier or NULL in case of an error.

Note: Cannot be called from Interrupt Service Routines.

Code Example

Refer to the Thread Examples section.

const char * osThreadGetName ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: name as null-terminated string.

The function osThreadGetName returns the pointer to the name string of the thread identified by parameter thread_id or NULL in case of an error.

Note: This function may be called from Interrupt Service Routines.

Code Example

void ThreadGetName_example (void) {
  osThreadId_t thread_id = osThreadGetId();
  const char* name = osThreadGetName(thread_id);
  if (name == NULL) {
    // Failed to get the thread name; not in a thread
  }
}

uint32_t osThreadGetClass ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: safety class of the specified thread.

The function osThreadGetClass returns safety class assigned to the thread identified by parameter thread_id. In case of an error, it returns osErrorId.

uint32_t osThreadGetZone ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: MPU protected zone of the specified thread.

The function osThreadGetZone returns the MPU Protected Zone value assigned to the thread identified by parameter thread_id. In case of an error, it returns osErrorId.

osThreadId_t osThreadGetId ( void )

Returns: thread ID for reference by other functions or NULL in case of error.

The function osThreadGetId returns the thread object ID of the currently running thread or NULL in case of an error.

Note: This function may be called from Interrupt Service Routines.

Code Example

void ThreadGetId_example (void) {
  osThreadId_t id;                              // id for the currently running thread
   
  id = osThreadGetId();
  if (id == NULL) {
    // Failed to get the id
  }
}

osThreadState_t osThreadGetState ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: current thread state of the specified thread.

The function osThreadGetState returns the state of the thread identified by parameter thread_id. In case it fails or if it is called from an ISR, it will return osThreadError, otherwise it returns the thread state (refer to osThreadState_t for the list of thread states).

Note: This function cannot be called from Interrupt Service Routines.

osStatus_t osThreadSetPriority	(	osThreadId_t	thread_id,
		osPriority_t	priority
	)

Parameters

[in]	thread_id	thread ID obtained by osThreadNew or osThreadGetId.
[in]	priority	new priority value for the thread function.

Returns: status code that indicates the execution status of the function.

The function osThreadSetPriority changes the priority of an active thread specified by the parameter thread_id to the priority specified by the parameter priority.

Possible osStatus_t return values:

osOK: the priority of the specified thread has been changed successfully.
osErrorParameter: thread_id is NULL or invalid or priority is incorrect.
osErrorResource: the thread is in an invalid state.
osErrorISR: the function osThreadSetPriority cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.

Code Example

#include "cmsis_os2.h"
 
void Thread_1 (void const *arg) {               // Thread function
  osThreadId_t id;                              // id for the currently running thread
  osStatus_t   status;                          // status of the executed function
 
  :
  id = osThreadGetId();                         // Obtain ID of current running thread
 
  status = osThreadSetPriority(id, osPriorityBelowNormal);  // Set thread priority
  if (status == osOK) {
    // Thread priority changed to BelowNormal
  }
  else {
    // Failed to set the priority
  }
  :
}

osPriority_t osThreadGetPriority ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: current priority value of the specified thread.

The function osThreadGetPriority returns the priority of an active thread specified by the parameter thread_id.

Possible osPriority_t return values:

priority: the priority of the specified thread.
osPriorityError: priority cannot be determined or is illegal. It is also returned when the function is called from Interrupt Service Routines.

Note: This function cannot be called from Interrupt Service Routines.

Code Example

#include "cmsis_os2.h"
 
void Thread_1 (void const *arg) {               // Thread function
  osThreadId_t id;                              // id for the currently running thread
  osPriority_t priority;                        // thread priority
   
  id = osThreadGetId();                         // Obtain ID of current running thread
  priority = osThreadGetPriority(id);           // Obtain the thread priority
}

osStatus_t osThreadYield ( void )

Returns: status code that indicates the execution status of the function.

The function osThreadYield passes control to the next thread with the same priority that is in the READY state. If there is no other thread with the same priority in state READY, then the current thread continues execution and no thread switch occurs. osThreadYield does not set the thread to state BLOCKED. Thus no thread with a lower priority will be scheduled even if threads in state READY are available.

Possible osStatus_t return values:

osOK: control has been passed to the next thread successfully.
osError: an unspecified error has occurred.
osErrorISR: the function osThreadYield cannot be called from interrupt service routines.

Note: This function cannot be called from Interrupt Service Routines.; This function has no impact when called when the kernel is locked, see osKernelLock.

Code Example

#include "cmsis_os2.h"
 
void Thread_1 (void const *arg) {               // Thread function
  osStatus_t status;                            // status of the executed function
  :
  while (1) {
    status = osThreadYield();
    if (status != osOK) {
      // an error occurred
    }
  }
}

osStatus_t osThreadSuspend ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: status code that indicates the execution status of the function.

The function osThreadSuspend suspends the execution of the thread identified by parameter thread_id. The thread is put into the BLOCKED state (osThreadBlocked). Suspending the running thread will cause a context switch to another thread in READY state immediately. The suspended thread is not executed until explicitly resumed with the function osThreadResume.

Threads that are already BLOCKED are removed from any wait list and become ready when they are resumed. Thus it is not recommended to suspend an already blocked thread.

Possible osStatus_t return values:

osOK: the thread has been suspended successfully.
osErrorParameter: thread_id is NULL or invalid.
osErrorResource: the thread is in an invalid state.
osErrorISR: the function osThreadSuspend cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.; This function must not be called to suspend the running thread when the kernel is locked, i.e. osKernelLock.

osStatus_t osThreadResume ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: status code that indicates the execution status of the function.

The function osThreadResume puts the thread identified by parameter thread_id (which has to be in BLOCKED state) back to the READY state. If the resumed thread has a higher priority than the running thread a context switch occurs immediately.

The thread becomes ready regardless of the reason why the thread was blocked. Thus it is not recommended to resume a thread not suspended by osThreadSuspend.

Functions that will put a thread into BLOCKED state are: osEventFlagsWait and osThreadFlagsWait, osDelay and osDelayUntil, osMutexAcquire and osSemaphoreAcquire, osMessageQueueGet, osMemoryPoolAlloc, osThreadJoin, osThreadSuspend.

Possible osStatus_t return values:

osOK: the thread has been resumed successfully.
osErrorParameter: thread_id is NULL or invalid.
osErrorResource: the thread is in an invalid state.
osErrorISR: the function osThreadResume cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.; This function may be called when kernel is locked (osKernelLock). Under this circumstances a potential context switch is delayed until the kernel gets unlocked, i.e. osKernelUnlock or osKernelRestoreLock.

osStatus_t osThreadDetach ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: status code that indicates the execution status of the function.

The function osThreadDetach changes the attribute of a thread (specified by thread_id) to osThreadDetached. Detached threads are not joinable with osThreadJoin. When a detached thread is terminated, all resources are returned to the system. The behavior of osThreadDetach on an already detached thread is undefined.

Possible osStatus_t return values:

osOK: the attribute of the specified thread has been changed to detached successfully.
osErrorParameter: thread_id is NULL or invalid.
osErrorResource: the thread is in an invalid state.
osErrorISR: the function osThreadDetach cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.

osStatus_t osThreadJoin ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: status code that indicates the execution status of the function.

The function osThreadJoin waits for the thread specified by thread_id to terminate. If that thread has already terminated, then osThreadJoin returns immediately. The thread must be joinable. By default threads are created with the attribute osThreadDetached.

Possible osStatus_t return values:

osOK: if the thread has already been terminated and joined or once the thread has been terminated and the join operations succeeds.
osErrorParameter: thread_id is NULL or invalid.
osErrorResource: the thread is in an invalid state (ex: not joinable).
osErrorISR: the function osThreadJoin cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.; Only one thread shall call osThreadJoin to join the target thread. If multiple threads try to join simultaneously with the same thread, the results are undefined.

__NO_RETURN void osThreadExit ( void )

The function osThreadExit terminates the calling thread. This allows the thread to be synchronized with osThreadJoin.

Note: This function cannot be called from Interrupt Service Routines.

Code Example

__NO_RETURN void worker (void *argument) {
  // do something
  osDelay(1000U);
  osThreadExit();
}

osStatus_t osThreadTerminate ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: status code that indicates the execution status of the function.

The function osThreadTerminate removes the thread specified by parameter thread_id from the list of active threads. If the thread is currently RUNNING, the thread terminates and the execution continues with the next READY thread. If no such thread exists, the function will not terminate the running thread, but return osErrorResource.

Possible osStatus_t return values:

osOK: the specified thread has been removed from the active thread list successfully.
osErrorParameter: thread_id is NULL or invalid.
osErrorResource: the thread is in an invalid state or no other READY thread exists.
osErrorISR: the function osThreadTerminate cannot be called from interrupt service routines.
osErrorSafetyClass: the calling thread safety class is lower than the safety class of the specified thread.

Note: This function cannot be called from Interrupt Service Routines.; Avoid calling the function with a thread_id that does not exist or has been terminated already.; osThreadTerminate destroys non-joinable threads and removes their thread_id from the system. Subsequent access to the thread_id (for example osThreadGetState) will return an osThreadError. Joinable threads will not be destroyed and return the status osThreadTerminated until they are joined with osThreadJoin.

Code Example

#include "cmsis_os2.h"
 
void Thread_1 (void *arg);                      // function prototype for Thread_1
 
void ThreadTerminate_example (void) {
  osStatus_t status;
  osThreadId_t id;
 
  id = osThreadNew(Thread_1, NULL, NULL);       // create the thread
                                                // do something
  status = osThreadTerminate(id);               // stop the thread
  if (status == osOK) {
                                                // Thread was terminated successfully
  }
  else {
                                                // Failed to terminate a thread
  }
}

uint32_t osThreadGetStackSize ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: stack size in bytes.

The function osThreadGetStackSize returns the stack size of the thread specified by parameter thread_id. In case of an error, it returns 0.

Note: This function cannot be called from Interrupt Service Routines.

uint32_t osThreadGetStackSpace ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: remaining stack space in bytes.

The function osThreadGetStackSpace returns the size of unused stack space for the thread specified by parameter thread_id. Stack watermark recording during execution needs to be enabled (refer to Thread Configuration). In case of an error, it returns 0.

Note: This function cannot be called from Interrupt Service Routines.

uint32_t osThreadGetCount ( void )

Returns: number of active threads.

The function osThreadGetCount returns the number of active threads or 0 in case of an error.

Note: This function cannot be called from Interrupt Service Routines.

uint32_t osThreadEnumerate	(	osThreadId_t *	thread_array,
		uint32_t	array_items
	)

Parameters

[out]	thread_array	pointer to array for retrieving thread IDs.
[in]	array_items	maximum number of items in array for retrieving thread IDs.

Returns: number of enumerated threads.

The function osThreadEnumerate returns the number of enumerated threads or 0 in case of an error.

Note: This function cannot be called from Interrupt Service Routines.

osStatus_t osThreadFeedWatchdog ( uint32_t ticks )

Parameters

[in] ticks time ticks value until the thread watchdog expires, or 0 to stop the watchdog

Returns: status code that indicates the execution status of the function.

The function osThreadFeedWatchdog restarts watchdog of the current running thread. If the thread watchdog is not fed again within the ticks interval osWatchdogAlarm_Handler will be called.

Possible osStatus_t return values:

osOK: the watchdog timer was restarted successfully.
osError: cannot be executed (kernel not running).
osErrorISR: the function osThreadFeedWatchdog cannot be called from interrupt service routines.

Note: This function cannot be called from Interrupt Service Routines.

Code Example:

#include "cmsis_os2.h"
 
void Thread_1 (void const *arg) {          // Thread function
  osStatus_t status;                       // Status of the executed function
  :
  while (1) {
    status = osThreadFeedWatchdog(500U);   // Feed thread watchdog for 500 ticks
    // verify status value here
    :
  }
}

osStatus_t osThreadProtectPrivileged ( void )

Returns: status code that indicates the execution status of the function.

The function osThreadProtectPrivileged disables creation of new privileged threads. After its successful execution, no new threads with privilege execution mode (osThreadPrivileged attribute) can be created. Kernel shall be in ready state or running when osThreadProtectPrivileged is called.

Possible osStatus_t return values:

osOK: the creation of new privileged threads is disabled.
osError: cannot be executed (kernel not ready).
osErrorISR: the function osThreadProtectPrivileged cannot be called from interrupt service routines.

Note: This function cannot be called from Interrupt Service Routines.

Code Example:

#include "cmsis_os2.h"
 
int main (void) {
  osStatus_t status;
  :
  status = osKernelInitialize();        // Initialize CMSIS-RTOS2 kernel
  // verify status value here.
  :                                     // Create privileged threads
  status = osThreadProtectPrivileged(); // Disable creation of new privileged threads.
  // verify status value here.
  :                                     // Start the kernel
}

osStatus_t osThreadSuspendClass	(	uint32_t	safety_class,
		uint32_t	mode
	)

Parameters

[in]	safety_class	safety class.
[in]	mode	safety mode.

Returns: status code that indicates the execution status of the function.

The function osThreadSuspendClass suspends execution of threads based on safety class assignment. safety_class provides the reference safety class value, while mode is considered as a bitmap that additionally specifies the safety classes to be suspended.

If osSafetyWithSameClass is set in mode than the threads with safety class value equal to safety_class will be suspended.
If osSafetyWithLowerClass is set in mode than the threads with safety class value lower than safety_class will be suspended.

Possible osStatus_t return values:

osOK: the threads with specified safety class have been suspended successfully.
osErrorParameter: safety_class is invalid.
osErrorResource: no other READY thread exists.
osErrorISR: the function osThreadSuspendClass is called from interrupt other than osWatchdogAlarm_Handler.
osErrorSafetyClass: the calling thread safety class is lower than the safety class specified by safety_class and mode.

Code Example:

#include "cmsis_os2.h"
 
void SuspendNonCriticalClasses (void) {
  osStatus_t status;
 
  status = osThreadSuspendClass(4U, osSafetyWithSameClass | osSafetyWithLowerClass); // Suspends threads with safety class 4 or lower
  // verify status value here.
}

osStatus_t osThreadResumeClass	(	uint32_t	safety_class,
		uint32_t	mode
	)

Parameters

[in]	safety_class	safety class.
[in]	mode	safety mode.

Returns: status code that indicates the execution status of the function.

The function osThreadResumeClass resumes execution of threads based on safety class assignment. safety_class provides the reference safety class value, while mode is considered as a bitmap that additionally specifies the safety classes to be resumed.

If osSafetyWithSameClass is set in mode than the threads with safety class value equal to safety_class will be resumed.
If osSafetyWithLowerClass is set in mode than the threads with safety class value lower than safety_class will be resumed.

Possible osStatus_t return values:

osOK: the threads with specified safety class have been resumed successfully.
osErrorParameter: safety_class is invalid.
osErrorISR: the function osThreadResumeClass is called from interrupt other than osWatchdogAlarm_Handler.
osErrorSafetyClass: the calling thread safety class is lower than the safety class specified by safety_class and mode.

Code Example:

#include "cmsis_os2.h"
 
void ResumeNonCriticalClasses (void) {
  osStatus_t status;
 
  status = osThreadResumeClass(4U, osSafetyWithSameClass | osSafetyWithLowerClass); // Resumes threads with safety class 4 or lower
  // verify status value here.
}

osStatus_t osThreadTerminateZone ( uint32_t zone )

Parameters

[in] zone MPU protected zone.

Returns: status code that indicates the execution status of the function.

The function osThreadTerminateZone terminates execution of threads assigned to the MPU Protected Zone as given by zone parameter.

Possible osStatus_t return values:

osOK: the threads within the specified MPU Protected Zone have been terminated successfully.
osErrorParameter: zone is invalid.
osErrorResource: no other READY thread exists.
osErrorISR: the function osThreadTerminateZone is called from interrupt other than fault.
osError: the function osThreadTerminateZone is called from thread.

Note: osThreadTerminateZone destroys non-joinable threads and removes their thread IDs from the system. Subsequent access to a terminated thread via its thread ID (for example osThreadGetState) will return an osThreadError. Joinable threads will not be destroyed and return the status osThreadTerminated until they are joined with osThreadJoin.

Code Example:

#include "cmsis_os2.h"
 
void TerminateFaultedThreads (void) {  // to be called from an exception fault context
  osStatus_t status;
 
  status = osThreadTerminateZone(3U); // Terminates threads assigned to MPU Protected Zone 3
  // verify status value here.
}

uint32_t osWatchdogAlarm_Handler ( osThreadId_t thread_id )

Parameters

[in] thread_id thread ID obtained by osThreadNew or osThreadGetId.

Returns: new watchdog reload value or 0 to stop the watchdog.

The callback function osWatchdogAlarm_Handler is called by the kernel when a thread watchdog expires. Parameter thread_id identifies the thread which has the expired thread watchdog. The function needs to be implemented in user application.

Return new reload value to restart the watchdog. Return 0 to stop the thread watchdog.

Note: The callback function is called from interrupt.; When multiple watchdogs expire in the same tick, this function is called for each thread with highest safety class first.

Code Example:

#include "cmsis_os2.h"
 
uint32_t osWatchdogAlarm_Handler (osThreadId_t thread_id) {
  uint32_t safety_class;
  uint32_t next_interval;
  safety_class = osThreadGetClass(thread_id);
  
  /* Handle the watchdog depending on how safety-critical is the thread */
  if (safety_class < ...){
    :
  } else {
    :
  }
 
  return next_interval;
}

void osZoneSetup_Callback ( uint32_t zone )

Parameters

[in] zone zone number.

The callback function osZoneSetup_Callback is called by the kernel when MPU Protected Zone changes. The function shall be implemented in user application.

Code Example:

/* Update MPU settings for newly activating Zone */
void osZoneSetup_Callback (uint32_t zone) {
 
  if (zone >= ZONES_NUM) {
    //Issue an error for incorrect zone value
  }
 
  ARM_MPU_Disable();
  ARM_MPU_Load(mpu_table[zone], MPU_REGIONS);
  ARM_MPU_Enable(MPU_CTRL_PRIVDEFENA_Msk);
}

ZONES_NUM is the total amount of zones allocated by the application. For ARM_MPU_... functions refer to MPU Functions in CMSIS-Core documentation.

Data Structures

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Functions

Description

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Thread Examples

Data Structure Documentation

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