JPH09160790A - Device and method for task schedule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the priority from being inverted with a small overhead by executing an exclusion execution part while making the priority high so that none of other tasks executing the same exclusive execution part interrupts when the exclusive execution part is executed. SOLUTION: At a resource control part 102, a resource use task registration part 110 registers the identifier of a resource that a task uses, and the identifier of the task and its execution prioritly in a resource management table 103. A priority decision part 111 determines the top execution priority among tasks registered in the same resource identifier in the resource management table 103. A priority change part 109 stores the top priority determined by the priority decision part 111 or the original execution priority of the task in the task management table 104 in response to the instruction of a task interruption processing part 101. A dispatch part 105 registers a task having the top priority from an execution wait queue in an execution queue and starts the task.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a task scheduling device and a task scheduling method for preventing priority inversion in a system for executing a plurality of tasks in parallel.

[0002]

2. Description of the Related Art FIG. 4 is an example of a program showing an exclusive control instruction that must be executed when a portion exclusively processed by a plurality of tasks is included. In FIG. 4, 4
Reference numeral 02 indicates a portion that must be exclusively processed, and the resource use request instruction 404 and the resource release request instruction 405 are executed before and after the portion. Reference numerals 401 and 403 denote processing portions of tasks that are not exclusively executed. Operations executed by a plurality of tasks including such an exclusively executed part will be described with reference to FIGS. 5 and 6.

FIG. 5 is an explanatory diagram of the task scheduling operation of the first conventional example. Three tasks, Task1, Task
2. Consider the case where Task3 executes in parallel. It is assumed that Task1, Task2, and Task3 have the highest execution priority, and that Task1 and Task3 use the same resource, that is, they are exclusively executed. Task2 with a high priority occurs while Task3 is executing the exclusive part (501). Task1 with higher priority occurs (502). If Task1 tries to execute the part that should be executed exclusively here, Task3 is already executing the exclusive part (using the exclusive resource), so Task1 waits in the locked state. So Ta
Control is transferred to sk2 (503). Task2 processing is completed and T
ask3 resumes execution (504), Task3 finishes the processing of the exclusive execution part, releases resources, and Task1 resumes execution (505). The processing of Task1 is completed, and the execution of Task3 is restarted (506).

FIG. 6 is an explanatory diagram of the task scheduling operation of the second conventional example. This is in the literature (Sha, L., Rajkum
ar, R. and Lehoczky, JP, "Priority Inheritance P
rotocols: An Approach to Real-Time Synchronizatio
n, "IEEE Transaction on Computers, vol.39, no.9, pp.1
175-1185, Sep. 1990), it uses the priority inheritance method. As in the case of FIG. 5, considering the case where three tasks, Task1, Task2, and Task3 are executed in parallel, from the highest execution priority, Task
It is assumed that the order is 1, Task2, and Task3, and Task1 and Task3 use the same resource, that is, they are exclusively executed. Task2 with high priority occurs while Task3 is executing the exclusive part (601). Task1 with higher priority occurs (602). Since Task3 is executing the exclusive part (using the exclusive resource), Task1 waits in the locked state. Here, the priority of Task3 is set to the same value as Task1, and Task3 executes the exclusive part (60
3), the processing of the exclusive execution part is completed, the resources are released, and the execution of Task1 is restarted (604). The processing of Task1 is completed, and control is transferred to Task2 (605). The processing of Task2 is completed and Task3 resumes execution (606).

[0005]

However, according to the above-mentioned conventional technique, a task with a high priority (Task1) is also excluded while a task with a low priority (Task3) is exclusively executed first. When you try to execute the target execution part, this task (Task1) becomes locked. At this time, when the task of the middle priority (Task2) starts executing, the execution of Task3 is made to wait until this end, and thus the task of the highest priority (Task1) is made to wait, and eventually Low task (Task2)
There was a problem that the inversion of the priority occurred that the task was terminated before the task with the higher priority (Task1). Furthermore, in order to avoid this, the priority inheritance method raises the priority of the low priority task (Task3) once the high priority task (Task1) is locked to execute the exclusive execution part. In order to execute the exclusive execution part, there is a problem that the number of task switching increases and the overhead increases.

In view of the above problems, the present invention manages priorities of tasks that execute the same exclusive execution unit in advance for each exclusive resource, and always executes the same exclusive execution unit when executing the exclusive execution unit. It is an object of the present invention to provide a task scheduling device and a task scheduling method in which priority is not reversed with a small overhead by executing a task with a high priority so as not to be interrupted by other tasks that execute the part.

[0007]

In order to solve the above problems, a task schedule device of the present invention is a task schedule device for performing multi-task processing, and comprises a task interruption processing unit that accepts an interrupt and a task interruption processing unit. A resource control unit activated by an instruction, a resource management table in which resource information used by a task is written and read by the resource control unit, and a task in which information regarding a currently executing task is written by the task interruption processing unit It is provided with a management table and a dispatch unit which determines a task to be executed next from the information in the task management table and activates the task.

The resource control unit registers a resource identifier used by a task in the resource management table, a resource user registration unit that registers the task identifier and the execution priority of the task, and the same resource in the resource management table. Among the tasks registered in the identifier, a priority determining unit that determines the highest execution priority, and the highest priority determined by the priority determining unit according to an instruction from the task interruption processing unit or the original execution of the task It is preferable to provide a priority order changing unit that stores the priority order in the priority order storage unit of the corresponding task in the task management table.

The task interruption processing unit examines the cause of the interruption and, if a resource use request is made, assigns the highest priority determined by the priority determination unit to the resource control unit as the corresponding portion of the task management table. It is desirable to instruct to write, and if the cause of the interrupt is a resource release request, it is desirable to instruct to write the original execution priority to the relevant part of the task management table.

The task management table has an execution queue for holding information on currently executing tasks and an execution queue for holding information on tasks waiting to be executed. The information on the tasks indicates the execution priority of the tasks. It is desirable to include.

It is preferable that the dispatch unit registers the task having the highest execution priority from the execution waiting queue in the execution queue and activates the task.

A task scheduling method of the present invention is a task scheduling method for performing multitask processing, wherein a task interruption processing procedure activated by an interrupt, a resource control procedure activated by an instruction of the task interruption processing procedure, And a dispatch processing procedure for deciding a task to be executed next and activating the task.

The resource control procedure is a resource control command determination procedure for determining an instruction from the task suspension processing procedure, and information about resources used by the task when the instruction from the task suspension processing procedure is task generation. Resource registration table for registering resources in the resource management table, and when the instruction from the task suspension processing procedure is a resource usage request, register to use the same resource from the information related to the resource used by the task in the resource management table. Priority determination procedure that determines the highest execution priority of the specified tasks, and priority restoration procedure that determines the original execution priority of the task when the instruction from the task suspension processing procedure is a resource release request And the execution priority determined in the priority determination procedure or the priority restoration procedure. It is desirable to have a priority changing procedure for changing the execution priority of the disk.

In the task suspension processing procedure, the cause of the interrupt is checked, and if a resource use request is made, the highest priority determined by the priority determination procedure is assigned to the relevant part of the task management table for the resource control procedure. It is desirable to instruct to write, and if the cause of the interrupt is a resource release request, it is desirable to instruct to write the original execution priority to the relevant part of the task management table.

It is desirable that the dispatch processing procedure decides a task having the highest execution priority among the executable tasks and activates the task.

According to the present invention, when the same resource is used by a plurality of tasks, the present invention executes the process of using the resource with the highest execution priority of the tasks that may use the resource. However, when the resource use request is processed, the same resource is not already being used by another task.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a task schedule device and a task schedule method thereof according to the present invention will be described with specific examples.

FIG. 1 is a block diagram of a task schedule device in an embodiment of the present invention. In the figure, the task interruption processing unit 101 examines an interrupt factor and determines a process according to the interrupt factor. The resource control unit 102 registers the resource identifier used by the task in the resource management table 103, the resource use task registration unit 110 that registers the task identifier and the task execution priority, and the same resource identifier in the resource management table 103. Priority determination unit 11 that determines the highest execution priority among the tasks registered in
1 and a priority changing unit 109 that stores the highest priority determined by the priority determining unit 111 according to an instruction from the task interruption processing unit 101 or the task's original execution priority in the task management table 104. The task management table 104 includes information 106 on the currently executing task.
Has a run queue (Run-Queue) that holds information about a task that can be executed next, and a queue (Ready-Queue) that holds information 108 about the next executable task. Dispatch unit 105
Registers the task with the highest execution priority from the execution-waiting queue (Ready-Queue) in the execution queue and starts the task. Causes of interruption include a new task registration, a resource use request by a task, and a resource release request by a task.

The task schedule device according to the embodiment of the present invention configured as described above will be described with reference to FIGS.
The operation will be described with reference to FIGS.

FIG. 2 is a flow chart showing the task scheduling method of the present invention. The interrupt causes the task interruption processing procedure 201 to be executed. If the interrupt factor is related to resource access, the resource control procedure 202 is executed. The dispatch processing procedure 203 determines the task to be executed next and activates the task.

The resource control procedure 202 first determines the resource control command in the resource control command determination procedure 211, and if the command is a resource use registration request, executes the resource use task registration procedure 212. If the command is a resource use request, the priority order determining procedure 213 is executed and the priority order changing procedure 215 is executed. If the command is a resource release request, the priority return procedure 214 is executed and the priority change procedure 215 is executed.

FIG. 3 is an operation explanatory diagram of task scheduling in the embodiment of the present invention, which shows scheduling when a task having an exclusive execution portion as shown in FIG. 4 executes. Three tasks, Task
Consider 1, Task2, Task3. It is assumed that the order of execution priority is Task1, Task2, and Task3 from the highest priority (Priority1
>Priority2> Priority3), Task1 and Task3 use the same resource, that is, execute exclusively. Assuming that the resource usage of three tasks is known in advance, that is, Task1 and Task3 are the same resource (Resource1).
And Task2 uses another resource (Resource2).

First, by issuing a resource use registration request to the task scheduling device before executing the task, the resource use task registration unit 110 registers the resource use information of the task in the resource management table 103 by the resource use task registration procedure 212. . At this time, Task1 and Task3 are registered as using the same resource (Resource1), and Task2 is registered as using another resource (Resource2).

First, Task 3 issues a resource use request command to the task scheduling device in order to execute the exclusive part. As a result, the priority order determination unit 111 uses the resource (R) used by Task3 registered in the resource management table 103 by the priority order determination procedure 213.
the highest priority task that uses esource1)
Earn Priority 1. The priority changing unit 109 uses the priority changing procedure 215 to save the task management table.
Write to the information holding unit 106 regarding Task3.

Next, the dispatch unit 105 continues the execution of Task3. At this time, Task3 is the execution priority Pri
It will be executed in ority1. If Task2 occurs while Task3 is executing the exclusive part, Task2
2 and Task3 is originally Priority3 (Priority2> Priori
ty3) but for the exclusive execution part Priority1
(Priority1> Priority2). Therefore Ta
sk3 is continuously executed until execution of the exclusive part is completed. When Task3 finishes the exclusive execution part, it issues a resource release request command to the task scheduling device. As a result, the priority order determination unit 111
The resource management table 10 is processed by the priority return procedure 214.
Acquire the original priority Priority3 of Task3 registered in 3. The priority changing unit 109 writes this in the information holding unit 106 regarding Task3 of the task management table by the priority changing procedure 215.

Next, by the dispatch unit 105, among the tasks that can be executed at this time, Task2 having a higher execution priority is given.
Is started (301). Task1 while Task2 is running
If Task1 occurs, Task1 has a higher execution priority (Priority1> Priority2), so Task1 starts executing (3
02). When the execution of Task1 ends, Task2, which has a higher execution priority, of the two tasks waiting to be executed at this point resumes execution (303), and when the execution of Task2 ends, Task3 resumes execution (304 ) Do.

[0027]

As described above, according to the task scheduling apparatus and the task scheduling method of the present invention,
When the same resource is used by multiple tasks, the processing that uses the resource with the highest priority of the tasks that may use the resource is executed. , The same resource is not already being used by another task, and the original execution priority will not be reversed. Further, since the resource information used by the task is registered in advance and the execution priority of the task is changed at the time of starting the execution of the exclusive execution part, the overhead required for switching the task can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a task schedule device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a task scheduling method according to an embodiment of the present invention.

FIG. 3 is an operation explanatory diagram of task scheduling in the embodiment of the present invention.

FIG. 4 is a diagram showing a part of a program example requiring exclusive control.

FIG. 5 is an operation explanatory diagram of task scheduling in the first conventional example.

FIG. 6 is an operation explanatory diagram of task scheduling in the second conventional example.

[Explanation of symbols]

 101 Task Suspension Processing Unit 102 Resource Control Unit 103 Resource Management Table 104 Task Management Table 105 Dispatcher 109 Priority Change Unit 110 Resource Use Task Registration Unit 111 Priority Order Determination Unit 201 Task Suspension Processing Procedure 202 Resource Control Procedure 203 Dispatch Processing Procedure

Claims (9)

[Claims] 1. A task schedule device for performing multi-task processing, a task interruption processing unit for accepting an interrupt, a resource control unit activated by an instruction from the task interruption processing unit, and a task used by the resource control unit. The resource management table in which the resource information to be written and read is performed, the task management table in which the information about the currently executing task is written by the task interruption processing unit, and the task to be executed next from the information in the task management table. A task scheduling device, comprising: a dispatch unit that determines and activates the task. 2. The resource control unit registers the identifier of the resource used by the task, the identifier of the task and the execution priority of the task in the resource management table, and the same resource management table in the resource management table. Among the tasks registered in the resource identifier, the priority determination unit that determines the highest execution priority, and the highest priority determined by the priority determination unit or the original task The task schedule device according to claim 1, further comprising: a priority change unit that stores the execution priority in a priority storage unit of a corresponding task in the task management table. 3. The task interruption processing section examines the cause of the interruption and, if a resource use request is made, assigns the highest priority order determined by the priority order determination section according to claim 2 to the resource control section. 3. The task schedule according to claim 2, wherein the task schedule is instructed to write to a corresponding part of the management table, and if the cause of the interrupt is a resource release request, the original execution priority is instructed to be written to the corresponding part of the task management table. apparatus. 4. The task management table has an execution queue that holds information about currently executing tasks and an execution queue that holds information about tasks waiting to be executed, and the information about the tasks is the execution priority of the tasks. The task scheduling device according to claim 1, further comprising: 5. The dispatch unit registers the task with the highest execution priority from the execution queue according to claim 4 in the execution queue according to claim 4, and activates the task. Item 1. The task schedule device according to item 1. 6. A task scheduling method for performing multi-task processing, a task interruption processing procedure activated by an interrupt, a resource control procedure activated by an instruction of the task interruption processing procedure, and a task to be executed next. And a dispatch processing procedure for activating the task. 7. The resource control procedure relates to a resource control command determination procedure for determining an instruction from a task suspension processing procedure and a resource used by the task when the instruction from the task suspension processing procedure is task creation. Use the same resource from the resource use task registration procedure for registering information in the resource management table and the resource related information used by the task in the resource management table when the instruction from the task suspension processing procedure is a resource use request. The priority determination procedure that determines the highest execution priority among the registered tasks, and the priority restoration that determines the original execution priority of the task when the instruction from the task suspension processing procedure is a resource release request. And the execution priority determined by the priority determination procedure or the priority restoration procedure. Task scheduling method according to claim 6, characterized in that a priority changing procedure for changing the execution priority of the disk. 8. The task interruption processing procedure examines the cause of interruption and, if a resource use request is made, gives the highest priority determined by the priority determination procedure according to claim 7 to the resource control procedure. 8. The task scheduling method according to claim 7, wherein the task scheduling method is instructed to write in a corresponding portion of the table, and when the interrupt factor is a resource release request, the original execution priority is instructed to be written in a corresponding portion of the task management table. 9. The task scheduling method according to claim 6, wherein the dispatch processing procedure determines the task having the highest execution priority among the executable tasks and activates the task.