framework/c/inc/le_thread.h File Reference

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Defines
#define	LE_THREAD_PRIORITY_RT_LOWEST   LE_THREAD_PRIORITY_RT_1
	Lowest real-time priority.
#define	LE_THREAD_PRIORITY_RT_HIGHEST   LE_THREAD_PRIORITY_RT_32
	Highest real-time priority.
Typedefs
typedef struct le_thread *	le_thread_Ref_t
typedef void *(*	le_thread_MainFunc_t )(void *context)
typedef void(*	le_thread_Destructor_t )(void *context)
Enumerations
enum	le_thread_Priority_t {   LE_THREAD_PRIORITY_IDLE = 0, LE_THREAD_PRIORITY_NORMAL, LE_THREAD_PRIORITY_RT_1, LE_THREAD_PRIORITY_RT_2,   LE_THREAD_PRIORITY_RT_3, LE_THREAD_PRIORITY_RT_4, LE_THREAD_PRIORITY_RT_5, LE_THREAD_PRIORITY_RT_6,   LE_THREAD_PRIORITY_RT_7, LE_THREAD_PRIORITY_RT_8, LE_THREAD_PRIORITY_RT_9, LE_THREAD_PRIORITY_RT_10,   LE_THREAD_PRIORITY_RT_11, LE_THREAD_PRIORITY_RT_12, LE_THREAD_PRIORITY_RT_13, LE_THREAD_PRIORITY_RT_14,   LE_THREAD_PRIORITY_RT_15, LE_THREAD_PRIORITY_RT_16, LE_THREAD_PRIORITY_RT_17, LE_THREAD_PRIORITY_RT_18,   LE_THREAD_PRIORITY_RT_19, LE_THREAD_PRIORITY_RT_20, LE_THREAD_PRIORITY_RT_21, LE_THREAD_PRIORITY_RT_22,   LE_THREAD_PRIORITY_RT_23, LE_THREAD_PRIORITY_RT_24, LE_THREAD_PRIORITY_RT_25, LE_THREAD_PRIORITY_RT_26,   LE_THREAD_PRIORITY_RT_27, LE_THREAD_PRIORITY_RT_28, LE_THREAD_PRIORITY_RT_29, LE_THREAD_PRIORITY_RT_30,   LE_THREAD_PRIORITY_RT_31, LE_THREAD_PRIORITY_RT_32 }
Functions
le_thread_Ref_t	le_thread_Create (const char *name, le_thread_MainFunc_t mainFunc, void *context)
le_result_t	le_thread_SetPriority (le_thread_Ref_t thread, le_thread_Priority_t priority)
le_result_t	le_thread_SetStackSize (le_thread_Ref_t thread, size_t size)
void	le_thread_SetJoinable (le_thread_Ref_t thread)
void	le_thread_Start (le_thread_Ref_t thread)
le_result_t	le_thread_Join (le_thread_Ref_t thread, void **resultValuePtr)
void	le_thread_Exit (void *resultValue)
le_result_t	le_thread_Cancel (le_thread_Ref_t threadToCancel)
le_thread_Ref_t	le_thread_GetCurrent (void)
void	le_thread_GetName (le_thread_Ref_t threadRef, char *buffPtr, size_t buffSize)
const char *	le_thread_GetMyName (void)
void	le_thread_AddDestructor (le_thread_Destructor_t destructor, void *context)
void	le_thread_AddChildDestructor (le_thread_Ref_t thread, le_thread_Destructor_t destructor, void *context)

---

Detailed Description

Legato Thread Control API include file.

Copyright (C) Sierra Wireless, Inc. 2014. All rights reserved. Use of this work is subject to license.

---

Typedef Documentation

typedef void(* le_thread_Destructor_t)(void *context)

Destructor functions for threads must look like this:

Parameters:

context

[IN] Context parameter that was passed into le_thread_SetDestructor() when this destructor was registered.

typedef void*(* le_thread_MainFunc_t)(void *context)

Main functions for threads must look like this:

Parameters:

context

[IN] Context value that was passed to le_thread_Create().

Returns:

Thread result value. If the thread is joinable, then this value can be obtained by another thread through a call to vt_thread_Join(). Otherwise, the return value is ignored.

typedef struct le_thread* le_thread_Ref_t

Reference to a thread of execution.

Note:

NULL can be used as an invalid value.

---

Enumeration Type Documentation

enum le_thread_Priority_t

Thread priority levels.

Real-time priority levels should be avoided unless absolutely necessary for the application. They are privileged levels and will therefore not be allowed unless the application is executed by an identity with the appropriate permissions. If a thread running at a real-time priority level does not block, no other thread at a lower priority level will run, so be careful with these.

Note:

Higher numbers are higher priority.

Enumerator:

LE_THREAD_PRIORITY_IDLE	Lowest priority level. Only runs when nothing else to do.
LE_THREAD_PRIORITY_NORMAL	Normal, non-real-time priority level. THIS IS THE DEFAULT.
LE_THREAD_PRIORITY_RT_1	Real-time priority level 1. The lowest realtime priority level.
LE_THREAD_PRIORITY_RT_2	Real-time priority level 2.
LE_THREAD_PRIORITY_RT_3	Real-time priority level 3.
LE_THREAD_PRIORITY_RT_4	Real-time priority level 4.
LE_THREAD_PRIORITY_RT_5	Real-time priority level 5.
LE_THREAD_PRIORITY_RT_6	Real-time priority level 6.
LE_THREAD_PRIORITY_RT_7	Real-time priority level 7.
LE_THREAD_PRIORITY_RT_8	Real-time priority level 8.
LE_THREAD_PRIORITY_RT_9	Real-time priority level 9.
LE_THREAD_PRIORITY_RT_10	Real-time priority level 10.
LE_THREAD_PRIORITY_RT_11	Real-time priority level 11.
LE_THREAD_PRIORITY_RT_12	Real-time priority level 12.
LE_THREAD_PRIORITY_RT_13	Real-time priority level 13.
LE_THREAD_PRIORITY_RT_14	Real-time priority level 14.
LE_THREAD_PRIORITY_RT_15	Real-time priority level 15.
LE_THREAD_PRIORITY_RT_16	Real-time priority level 16.
LE_THREAD_PRIORITY_RT_17	Real-time priority level 17.
LE_THREAD_PRIORITY_RT_18	Real-time priority level 18.
LE_THREAD_PRIORITY_RT_19	Real-time priority level 19.
LE_THREAD_PRIORITY_RT_20	Real-time priority level 20.
LE_THREAD_PRIORITY_RT_21	Real-time priority level 21.
LE_THREAD_PRIORITY_RT_22	Real-time priority level 22.
LE_THREAD_PRIORITY_RT_23	Real-time priority level 23.
LE_THREAD_PRIORITY_RT_24	Real-time priority level 24.
LE_THREAD_PRIORITY_RT_25	Real-time priority level 25.
LE_THREAD_PRIORITY_RT_26	Real-time priority level 26.
LE_THREAD_PRIORITY_RT_27	Real-time priority level 27.
LE_THREAD_PRIORITY_RT_28	Real-time priority level 28.
LE_THREAD_PRIORITY_RT_29	Real-time priority level 29.
LE_THREAD_PRIORITY_RT_30	Real-time priority level 30.
LE_THREAD_PRIORITY_RT_31	Real-time priority level 31.
LE_THREAD_PRIORITY_RT_32	Real-time priority level 32.

---

Function Documentation

void le_thread_AddChildDestructor	(	le_thread_Ref_t	thread,
		le_thread_Destructor_t	destructor,
		void *	context
	)

Registers a destructor function for a child thread. The destructor will be called by the child thread just before it terminates.

This can only be done before the child thread is started. After that, only the child thread can add its own destructors.

The reason for allowing another thread to register a destructor function is to avoid a race condition that can cause resource leakage when a parent thread passes dynamically allocated resources to threads that they create. This is only a problem if the child thread is expected to release the resources when they are finished with them, and the child thread may get cancelled at any time.

For example, a thread T1 could allocate an object from a memory pool, create a thread T2, and pass that object to T2 for processing and release. T2 could register a destructor function to release the resource whenever it terminates, whether through cancellation or normal exit. But, if it's possible that T2 could get cancelled before it even has a chance to register a destructor function for itself, the memory pool object could never get released. So, we allow T1 to register a destructor function for T2 before starting T2.

See Thread Destructors for more information on destructors.

Parameters:

[in]	thread	Thread to attach the destructor to.
[in]	destructor	Function to be called.
[in]	context	Parameter to pass to the destructor.

void le_thread_AddDestructor	(	le_thread_Destructor_t	destructor,
		void *	context
	)

Registers a destructor function for the calling thread. The destructor will be called by that thread just before it terminates.

A thread can register its own destructor functions any time.

See Thread Destructors for more information on destructors.

Parameters:

[in]	destructor	Function to be called.
[in]	context	Parameter to pass to the destructor.

le_result_t le_thread_Cancel

(

le_thread_Ref_t

threadToCancel

)

Tells another thread to terminate. Returns immediately, but the termination of the thread happens asynchronously and is not guaranteed to occur when this function returns.

Returns:

• LE_OK if successful.
• LE_NOT_FOUND if the thread doesn't exist.

le_thread_Ref_t le_thread_Create	(	const char *	name,
		le_thread_MainFunc_t	mainFunc,
		void *	context
	)

Creates a new Legato thread of execution. After creating the thread, you have the opportunity to set attributes before it starts. It won't start until le_thread_Start() is called.

Returns:

A reference to the thread (doesn't return if fails).

Parameters:

[in]	name	Thread name.
[in]	mainFunc	Thread's main function.
[in]	context	Value to pass to mainFunc when it is called.

void le_thread_Exit

(

void *

resultValue

)

Terminates the calling thread.

Parameters:

[in]

resultValue

Result value. If this thread is joinable, this result can be obtained by another thread calling le_thread_Join() on this thread.

le_thread_Ref_t le_thread_GetCurrent

(

void

)

Gets the calling thread's thread reference.

Returns:

Calling thread's thread reference.

const char* le_thread_GetMyName

(

void

)

Gets the name of the calling thread.

void le_thread_GetName	(	le_thread_Ref_t	threadRef,
		char *	buffPtr,
		size_t	buffSize
	)

Gets the name of a given thread.

Parameters:

[in]	threadRef
[out]	buffPtr	Buffer to store the name of the thread.
[in]	buffSize	Size of the buffer.

le_result_t le_thread_Join	(	le_thread_Ref_t	thread,
		void **	resultValuePtr
	)

"Joins" the calling thread with another thread. Blocks the calling thread until the other thread finishes.

After a thread has been joined with, its thread reference is no longer valid and must never be used again.

The other thread's result value (the value it returned from its main function or passed into le_thread_Exit()) can be obtained.

Returns:

• LE_OK if successful.
• LE_DEADLOCK if a thread tries to join with itself or two threads try to join each other.
• LE_NOT_FOUND if the other thread doesn't exist.
• LE_NOT_POSSIBLE if the other thread can't be joined with.

Warning:

The other thread must be "joinable". See le_thread_SetJoinable();

It's an error for two or more threads try to join with the same thread.

Parameters:

[in]	thread
[out]	resultValuePtr	Ptr to where the finished thread's result value will be stored. Can be NULL if the result is not needed.

void le_thread_SetJoinable

(

le_thread_Ref_t

thread

)

Makes a thread "joinable", meaning that when it finishes, it will remain in existence until another thread "joins" with it by calling le_thread_Join(). By default, threads are not joinable and will be destroyed automatically when they finish.

Parameters:

[in]

thread

le_result_t le_thread_SetPriority	(	le_thread_Ref_t	thread,
		le_thread_Priority_t	priority
	)

Sets the priority of a thread.

Returns:

• LE_OK if successful.
• LE_NOT_PERMITTED if the calling thread doesn't have the necessary permission levels to use the requested priority level.
• LE_OUT_OF_RANGE if the priority level requested is out of range.

Parameters:

[in]	thread
[in]	priority

le_result_t le_thread_SetStackSize	(	le_thread_Ref_t	thread,
		size_t	size
	)

Sets the stack size of a thread.

Note:

It's generally not necessary to set the stack size. Some reasons why you might are:

• to increase it beyond the system's default stack size to prevent overflow for a thread that makes extremely heavy use of the stack;
• to decrease it to save memory when:
  • running in a system that does not support virtual memory
  • the thread has very tight real-time constraints that require that the stack memory be locked into physical memory to avoid page faults.

Returns:

• LE_OK if successful.
• LE_OVERFLOW if the stack size requested is too small.
• LE_OUT_OF_RANGE if the stack size requested is too large.

Parameters:

[in]	thread
[in]	size	Stack size, in bytes. May be rounded up to the nearest virtual memory page size.

void le_thread_Start

(

le_thread_Ref_t

thread

)

Starts a new Legato execution thread. After creating the thread, you have the opportunity to set attributes before it starts. It won't start until le_thread_Start() is called.

Parameters:

[in]

thread