SMP Scheduler

The scheduler nodes can be in four states. More...

Collaboration diagram for SMP Scheduler:

Modules
	Deterministic Priority SMP Scheduler
	This is an implementation of the global fixed priority scheduler (G-FP).
	Simple Priority SMP Scheduler
	The Simple Priority SMP Scheduler allocates a processor for the processor count highest priority ready threads.

Files
file	schedulersmp.h
	SMP Scheduler API.
file	schedulersmpimpl.h
	SMP Scheduler Implementation.

Data Structures
struct	Scheduler_SMP_Context
	Scheduler context specialization for SMP schedulers. More...
struct	Scheduler_SMP_Node
	Scheduler node specialization for SMP schedulers. More...

Typedefs
typedef Scheduler_Node *(*	Scheduler_SMP_Get_highest_ready) (Scheduler_Context *context, Scheduler_Node *node)
typedef Scheduler_Node *(*	Scheduler_SMP_Get_lowest_scheduled) (Scheduler_Context *context, Scheduler_Node *filter, Chain_Node_order order)
typedef void(*	Scheduler_SMP_Extract) (Scheduler_Context *context, Scheduler_Node *node_to_extract)
typedef void(*	Scheduler_SMP_Insert) (Scheduler_Context *context, Scheduler_Node *node_to_insert)
typedef void(*	Scheduler_SMP_Move) (Scheduler_Context *context, Scheduler_Node *node_to_move)
typedef void(*	Scheduler_SMP_Update) (Scheduler_Context *context, Scheduler_Node *node_to_update, Priority_Control new_priority)
typedef Thread_Control *(*	Scheduler_SMP_Enqueue) (Scheduler_Context *context, Scheduler_Node *node_to_enqueue, Thread_Control *needs_help)
typedef Thread_Control *(*	Scheduler_SMP_Enqueue_scheduled) (Scheduler_Context *context, Scheduler_Node *node_to_enqueue)
typedef void(*	Scheduler_SMP_Allocate_processor) (Scheduler_Context *context, Thread_Control *scheduled, Thread_Control *victim)

Enumerations
enum	Scheduler_SMP_Node_state { SCHEDULER_SMP_NODE_BLOCKED, SCHEDULER_SMP_NODE_SCHEDULED, SCHEDULER_SMP_NODE_READY }
	SMP scheduler node states. More...

Functions
void	_Scheduler_SMP_Start_idle (const Scheduler_Control *scheduler, Thread_Control *thread, struct Per_CPU_Control *cpu)

Variables
const bool	_Scheduler_SMP_Node_valid_state_changes [3][3]

Detailed Description

The scheduler nodes can be in four states.

• SCHEDULER_SMP_NODE_BLOCKED,
• SCHEDULER_SMP_NODE_SCHEDULED, and
• SCHEDULER_SMP_NODE_READY.

State transitions are triggered via basic operations

• _Scheduler_SMP_Enqueue_ordered(),
• _Scheduler_SMP_Enqueue_scheduled_ordered(), and
• _Scheduler_SMP_Block().

During system initialization each processor of the scheduler instance starts with an idle thread assigned to it. Lets have a look at an example with two idle threads I and J with priority 5. We also have blocked threads A, B and C with priorities 1, 2 and 3 respectively. The scheduler nodes are ordered with respect to the thread priority from left to right in the below diagrams. The highest priority node (lowest priority number) is the leftmost node. Since the processor assignment is independent of the thread priority the processor indices may move from one state to the other.

Lets start A. For this an enqueue operation is performed.

Lets start C.

Lets start B.

Lets change the priority of thread A to 4.

Now perform a blocking operation with thread B. Please note that thread A migrated now from processor 0 to processor 1 and thread C still executes on processor 1.

Enumeration Type Documentation

Scheduler_SMP_Node_state

enum Scheduler_SMP_Node_state

SMP scheduler node states.

Enumerator
SCHEDULER_SMP_NODE_BLOCKED	This scheduler node is blocked. A scheduler node is blocked if the corresponding thread is not ready.
SCHEDULER_SMP_NODE_SCHEDULED	The scheduler node is scheduled. A scheduler node is scheduled if the corresponding thread is ready and the scheduler allocated a processor for it. A scheduled node is assigned to exactly one processor. The count of scheduled nodes in this scheduler instance equals the processor count owned by the scheduler instance.
SCHEDULER_SMP_NODE_READY	This scheduler node is ready. A scheduler node is ready if the corresponding thread is ready and the scheduler did not allocate a processor for it.