/**
* @file
*
* @brief SMP Scheduler Implementation
*
* @ingroup ScoreSchedulerSMP
*/
/*
* Copyright (c) 2013-2014 embedded brains GmbH. All rights reserved.
*
* embedded brains GmbH
* Dornierstr. 4
* 82178 Puchheim
* Germany
* <rtems@embedded-brains.de>
*
* The license and distribution terms for this file may be
* found in the file LICENSE in this distribution or at
* http://www.rtems.org/license/LICENSE.
*/
#ifndef _RTEMS_SCORE_SCHEDULERSMPIMPL_H
#define _RTEMS_SCORE_SCHEDULERSMPIMPL_H
#include <rtems/score/schedulersmp.h>
#include <rtems/score/assert.h>
#include <rtems/score/chainimpl.h>
#include <rtems/score/schedulersimpleimpl.h>
#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */
/**
* @addtogroup ScoreSchedulerSMP
*
* The scheduler nodes can be in four states
* - @ref SCHEDULER_SMP_NODE_BLOCKED,
* - @ref SCHEDULER_SMP_NODE_SCHEDULED, and
* - @ref SCHEDULER_SMP_NODE_READY.
*
* State transitions are triggered via basic operations
* - _Scheduler_SMP_Enqueue_ordered(),
* - _Scheduler_SMP_Enqueue_scheduled_ordered(), and
* - _Scheduler_SMP_Block().
*
* @dot
* digraph {
* node [style="filled"];
*
* bs [label="BLOCKED"];
* ss [label="SCHEDULED", fillcolor="green"];
* rs [label="READY", fillcolor="red"];
*
* edge [label="enqueue"];
* edge [fontcolor="darkgreen", color="darkgreen"];
*
* bs -> ss;
*
* edge [fontcolor="red", color="red"];
*
* bs -> rs;
*
* edge [label="enqueue other"];
*
* ss -> rs;
*
* edge [label="block"];
* edge [fontcolor="black", color="black"];
*
* ss -> bs;
* rs -> bs;
*
* edge [label="block other"];
* edge [fontcolor="darkgreen", color="darkgreen"];
*
* rs -> ss;
* }
* @enddot
*
* 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.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
* subgraph {
* rank = same;
*
* i [label="I (5)", fillcolor="green"];
* j [label="J (5)", fillcolor="green"];
* a [label="A (1)"];
* b [label="B (2)"];
* c [label="C (3)"];
* i -> j;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* i -> p0;
* j -> p1;
* }
* @enddot
*
* Lets start A. For this an enqueue operation is performed.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
*
* subgraph {
* rank = same;
*
* i [label="I (5)", fillcolor="green"];
* j [label="J (5)", fillcolor="red"];
* a [label="A (1)", fillcolor="green"];
* b [label="B (2)"];
* c [label="C (3)"];
* a -> i;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* i -> p0;
* a -> p1;
* }
* @enddot
*
* Lets start C.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
*
* subgraph {
* rank = same;
*
* a [label="A (1)", fillcolor="green"];
* c [label="C (3)", fillcolor="green"];
* i [label="I (5)", fillcolor="red"];
* j [label="J (5)", fillcolor="red"];
* b [label="B (2)"];
* a -> c;
* i -> j;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* c -> p0;
* a -> p1;
* }
* @enddot
*
* Lets start B.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
*
* subgraph {
* rank = same;
*
* a [label="A (1)", fillcolor="green"];
* b [label="B (2)", fillcolor="green"];
* c [label="C (3)", fillcolor="red"];
* i [label="I (5)", fillcolor="red"];
* j [label="J (5)", fillcolor="red"];
* a -> b;
* c -> i -> j;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* b -> p0;
* a -> p1;
* }
* @enddot
*
* Lets change the priority of thread A to 4.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
*
* subgraph {
* rank = same;
*
* b [label="B (2)", fillcolor="green"];
* c [label="C (3)", fillcolor="green"];
* a [label="A (4)", fillcolor="red"];
* i [label="I (5)", fillcolor="red"];
* j [label="J (5)", fillcolor="red"];
* b -> c;
* a -> i -> j;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* b -> p0;
* c -> p1;
* }
* @enddot
*
* 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.
*
* @dot
* digraph {
* node [style="filled"];
* edge [dir="none"];
*
* subgraph {
* rank = same;
*
* c [label="C (3)", fillcolor="green"];
* a [label="A (4)", fillcolor="green"];
* i [label="I (5)", fillcolor="red"];
* j [label="J (5)", fillcolor="red"];
* b [label="B (2)"];
* c -> a;
* i -> j;
* }
*
* subgraph {
* rank = same;
*
* p0 [label="PROCESSOR 0", shape="box"];
* p1 [label="PROCESSOR 1", shape="box"];
* }
*
* a -> p0;
* c -> p1;
* }
* @enddot
*
* @{
*/
typedef Thread_Control *( *Scheduler_SMP_Get_highest_ready )(
Scheduler_Context *context
);
typedef void ( *Scheduler_SMP_Extract )(
Scheduler_Context *context,
Thread_Control *thread
);
typedef void ( *Scheduler_SMP_Insert )(
Scheduler_Context *context,
Thread_Control *thread_to_insert
);
typedef void ( *Scheduler_SMP_Move )(
Scheduler_Context *context,
Thread_Control *thread_to_move
);
typedef void ( *Scheduler_SMP_Update )(
Scheduler_Context *context,
Scheduler_Node *node,
Priority_Control new_priority
);
typedef void ( *Scheduler_SMP_Enqueue )(
Scheduler_Context *context,
Thread_Control *thread_to_enqueue
);
static inline Scheduler_SMP_Context *_Scheduler_SMP_Get_self(
Scheduler_Context *context
)
{
return (Scheduler_SMP_Context *) context;
}
static inline void _Scheduler_SMP_Initialize(
Scheduler_SMP_Context *self
)
{
_Chain_Initialize_empty( &self->Scheduled );
}
static inline Scheduler_SMP_Node *_Scheduler_SMP_Node_get(
Thread_Control *thread
)
{
return (Scheduler_SMP_Node *) _Scheduler_Node_get( thread );
}
static inline void _Scheduler_SMP_Node_initialize(
Scheduler_SMP_Node *node
)
{
node->state = SCHEDULER_SMP_NODE_BLOCKED;
}
extern const bool _Scheduler_SMP_Node_valid_state_changes[ 3 ][ 3 ];
static inline void _Scheduler_SMP_Node_change_state(
Scheduler_SMP_Node *node,
Scheduler_SMP_Node_state new_state
)
{
_Assert(
_Scheduler_SMP_Node_valid_state_changes[ node->state ][ new_state ]
);
node->state = new_state;
}
static inline bool _Scheduler_SMP_Is_processor_owned_by_us(
const Scheduler_SMP_Context *self,
const Per_CPU_Control *cpu
)
{
return cpu->scheduler_context == &self->Base;
}
static inline void _Scheduler_SMP_Update_heir(
Per_CPU_Control *cpu_self,
Per_CPU_Control *cpu_for_heir,
Thread_Control *heir
)
{
cpu_for_heir->heir = heir;
/*
* It is critical that we first update the heir and then the dispatch
* necessary so that _Thread_Get_heir_and_make_it_executing() cannot miss an
* update.
*/
_Atomic_Fence( ATOMIC_ORDER_SEQ_CST );
/*
* Only update the dispatch necessary indicator if not already set to
* avoid superfluous inter-processor interrupts.
*/
if ( !cpu_for_heir->dispatch_necessary ) {
cpu_for_heir->dispatch_necessary = true;
if ( cpu_for_heir != cpu_self ) {
_Per_CPU_Send_interrupt( cpu_for_heir );
}
}
}
static inline void _Scheduler_SMP_Allocate_processor(
Scheduler_SMP_Context *self,
Thread_Control *scheduled,
Thread_Control *victim
)
{
Scheduler_SMP_Node *scheduled_node = _Scheduler_SMP_Node_get( scheduled );
Per_CPU_Control *cpu_of_scheduled = _Thread_Get_CPU( scheduled );
Per_CPU_Control *cpu_of_victim = _Thread_Get_CPU( victim );
Per_CPU_Control *cpu_self = _Per_CPU_Get();
Thread_Control *heir;
_Scheduler_SMP_Node_change_state(
scheduled_node,
SCHEDULER_SMP_NODE_SCHEDULED
);
_Assert( _ISR_Get_level() != 0 );
if ( _Thread_Is_executing_on_a_processor( scheduled ) ) {
if ( _Scheduler_SMP_Is_processor_owned_by_us( self, cpu_of_scheduled ) ) {
heir = cpu_of_scheduled->heir;
_Scheduler_SMP_Update_heir( cpu_self, cpu_of_scheduled, scheduled );
} else {
/* We have to force a migration to our processor set */
_Assert( scheduled->debug_real_cpu->heir != scheduled );
heir = scheduled;
}
} else {
heir = scheduled;
}
if ( heir != victim ) {
_Thread_Set_CPU( heir, cpu_of_victim );
_Scheduler_SMP_Update_heir( cpu_self, cpu_of_victim, heir );
}
}
static inline Thread_Control *_Scheduler_SMP_Get_lowest_scheduled(
Scheduler_SMP_Context *self
)
{
Thread_Control *lowest_ready = NULL;
Chain_Control *scheduled = &self->Scheduled;
if ( !_Chain_Is_empty( scheduled ) ) {
lowest_ready = (Thread_Control *) _Chain_Last( scheduled );
}
return lowest_ready;
}
/**
* @brief Enqueues a thread according to the specified order function.
*
* The thread must not be in the scheduled state.
*
* @param[in] context The scheduler instance context.
* @param[in] thread The thread to enqueue.
* @param[in] order The order function.
* @param[in] insert_ready Function to insert a node into the set of ready
* nodes.
* @param[in] insert_scheduled Function to insert a node into the set of
* scheduled nodes.
* @param[in] move_from_scheduled_to_ready Function to move a node from the set
* of scheduled nodes to the set of ready nodes.
*/
static inline void _Scheduler_SMP_Enqueue_ordered(
Scheduler_Context *context,
Thread_Control *thread,
Chain_Node_order order,
Scheduler_SMP_Insert insert_ready,
Scheduler_SMP_Insert insert_scheduled,
Scheduler_SMP_Move move_from_scheduled_to_ready
)
{
Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
Thread_Control *lowest_scheduled =
_Scheduler_SMP_Get_lowest_scheduled( self );
_Assert( lowest_scheduled != NULL );
if ( ( *order )( &thread->Object.Node, &lowest_scheduled->Object.Node ) ) {
Scheduler_SMP_Node *lowest_scheduled_node =
_Scheduler_SMP_Node_get( lowest_scheduled );
_Scheduler_SMP_Node_change_state(
lowest_scheduled_node,
SCHEDULER_SMP_NODE_READY
);
_Scheduler_SMP_Allocate_processor( self, thread, lowest_scheduled );
( *insert_scheduled )( &self->Base, thread );
( *move_from_scheduled_to_ready )( &self->Base, lowest_scheduled );
} else {
( *insert_ready )( &self->Base, thread );
}
}
/**
* @brief Enqueues a scheduled thread according to the specified order
* function.
*
* @param[in] context The scheduler instance context.
* @param[in] thread The thread to enqueue.
* @param[in] order The order function.
* @param[in] get_highest_ready Function to get the highest ready node.
* @param[in] insert_ready Function to insert a node into the set of ready
* nodes.
* @param[in] insert_scheduled Function to insert a node into the set of
* scheduled nodes.
* @param[in] move_from_ready_to_scheduled Function to move a node from the set
* of ready nodes to the set of scheduled nodes.
*/
static inline void _Scheduler_SMP_Enqueue_scheduled_ordered(
Scheduler_Context *context,
Thread_Control *thread,
Chain_Node_order order,
Scheduler_SMP_Get_highest_ready get_highest_ready,
Scheduler_SMP_Insert insert_ready,
Scheduler_SMP_Insert insert_scheduled,
Scheduler_SMP_Move move_from_ready_to_scheduled
)
{
Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
Scheduler_SMP_Node *node = _Scheduler_SMP_Node_get( thread );
Thread_Control *highest_ready = ( *get_highest_ready )( &self->Base );
_Assert( highest_ready != NULL );
/*
* The thread has been extracted from the scheduled chain. We have to place
* it now on the scheduled or ready set.
*/
if ( ( *order )( &thread->Object.Node, &highest_ready->Object.Node ) ) {
( *insert_scheduled )( &self->Base, thread );
} else {
_Scheduler_SMP_Node_change_state( node, SCHEDULER_SMP_NODE_READY );
_Scheduler_SMP_Allocate_processor( self, highest_ready, thread );
( *insert_ready )( &self->Base, thread );
( *move_from_ready_to_scheduled )( &self->Base, highest_ready );
}
}
static inline void _Scheduler_SMP_Extract_from_scheduled(
Thread_Control *thread
)
{
_Chain_Extract_unprotected( &thread->Object.Node );
}
static inline void _Scheduler_SMP_Schedule_highest_ready(
Scheduler_Context *context,
Thread_Control *victim,
Scheduler_SMP_Get_highest_ready get_highest_ready,
Scheduler_SMP_Move move_from_ready_to_scheduled
)
{
Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
Thread_Control *highest_ready = ( *get_highest_ready )( &self->Base );
_Scheduler_SMP_Allocate_processor( self, highest_ready, victim );
( *move_from_ready_to_scheduled )( &self->Base, highest_ready );
}
/**
* @brief Blocks a thread.
*
* @param[in] context The scheduler instance context.
* @param[in] thread The thread of the scheduling operation.
* @param[in] extract_from_ready Function to extract a node from the set of
* ready nodes.
* @param[in] get_highest_ready Function to get the highest ready node.
* @param[in] move_from_ready_to_scheduled Function to move a node from the set
* of ready nodes to the set of scheduled nodes.
*/
static inline void _Scheduler_SMP_Block(
Scheduler_Context *context,
Thread_Control *thread,
Scheduler_SMP_Extract extract_from_ready,
Scheduler_SMP_Get_highest_ready get_highest_ready,
Scheduler_SMP_Move move_from_ready_to_scheduled
)
{
Scheduler_SMP_Node *node = _Scheduler_SMP_Node_get( thread );
bool is_scheduled = node->state == SCHEDULER_SMP_NODE_SCHEDULED;
_Scheduler_SMP_Node_change_state( node, SCHEDULER_SMP_NODE_BLOCKED );
if ( is_scheduled ) {
_Scheduler_SMP_Extract_from_scheduled( thread );
_Scheduler_SMP_Schedule_highest_ready(
context,
thread,
get_highest_ready,
move_from_ready_to_scheduled
);
} else {
( *extract_from_ready )( context, thread );
}
}
static inline void _Scheduler_SMP_Unblock(
Scheduler_Context *context,
Thread_Control *thread,
Scheduler_SMP_Enqueue enqueue_fifo
)
{
Scheduler_SMP_Node *node = _Scheduler_SMP_Node_get( thread );
_Scheduler_SMP_Node_change_state( node, SCHEDULER_SMP_NODE_READY );
( *enqueue_fifo )( context, thread );
}
static inline void _Scheduler_SMP_Change_priority(
Scheduler_Context *context,
Thread_Control *thread,
Priority_Control new_priority,
bool prepend_it,
Scheduler_SMP_Extract extract_from_ready,
Scheduler_SMP_Update update,
Scheduler_SMP_Enqueue enqueue_fifo,
Scheduler_SMP_Enqueue enqueue_lifo,
Scheduler_SMP_Enqueue enqueue_scheduled_fifo,
Scheduler_SMP_Enqueue enqueue_scheduled_lifo
)
{
Scheduler_SMP_Node *node = _Scheduler_SMP_Node_get( thread );
if ( node->state == SCHEDULER_SMP_NODE_SCHEDULED ) {
_Scheduler_SMP_Extract_from_scheduled( thread );
( *update )( context, &node->Base, new_priority );
if ( prepend_it ) {
( *enqueue_scheduled_lifo )( context, thread );
} else {
( *enqueue_scheduled_fifo )( context, thread );
}
} else {
( *extract_from_ready )( context, thread );
( *update )( context, &node->Base, new_priority );
if ( prepend_it ) {
( *enqueue_lifo )( context, thread );
} else {
( *enqueue_fifo )( context, thread );
}
}
}
static inline void _Scheduler_SMP_Insert_scheduled_lifo(
Scheduler_Context *context,
Thread_Control *thread
)
{
Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
_Chain_Insert_ordered_unprotected(
&self->Scheduled,
&thread->Object.Node,
_Scheduler_simple_Insert_priority_lifo_order
);
}
static inline void _Scheduler_SMP_Insert_scheduled_fifo(
Scheduler_Context *context,
Thread_Control *thread
)
{
Scheduler_SMP_Context *self = _Scheduler_SMP_Get_self( context );
_Chain_Insert_ordered_unprotected(
&self->Scheduled,
&thread->Object.Node,
_Scheduler_simple_Insert_priority_fifo_order
);
}
/** @} */
#ifdef __cplusplus
}
#endif /* __cplusplus */
#endif /* _RTEMS_SCORE_SCHEDULERSMPIMPL_H */