JPH05143370A - Multi-task computer - Google Patents

Abstract

PURPOSE:To suppress the execution delay of a task with high priority order to a minimum by saving the context of a using task and starting exceptional processing when the exceptional processing routine of the using task is defined, and when not defined, setting up a task to be executed to a computer queuing state without processing it. CONSTITUTION:When a computer resource is being used, the priority of a task A is compared with that of a task C. When the priority of the task C is equal or lower to/than that of the task A, the task C is set up to a computer queuing state and the processing is ended. When the priority of the task C is higher, the priority of the task A is saved and raised up to the priority of the task C. Then whether the exceptional processing routine of the task A has been defined or not is judged, and when the routine has been defined, the context of the task A is saved and the exceptional processing routine of the task A is started. When the routine has not been defined yet, the task C is set up to the computer queuing state without executing the processing of the task A to end the current processing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is used for priority processing in an operating system. The present invention relates to a multi-task computer capable of minimizing a delay in execution of a task having a high priority in priority processing of a plurality of tasks competing for computer resources.

[0002]

2. Description of the Related Art First, problems with regard to priorities in a plurality of tasks competing for computer resources will be described with an example. Next, a conventional method for solving this problem will be described. FIG. 7 is a diagram showing a configuration of a task control block in the conventional example, and FIG. 8 is a flow chart showing a flow of resource acquisition processing in the conventional example.

Here, a system that executes three tasks A, B, and C is targeted, and these tasks have respective execution priorities, and the priority is higher in the order of A <B <C. .. Further, the tasks A and C use the computer resource X, and this computer resource X cannot be used by a plurality of tasks at the same time (can be used exclusively).
I shall.

Now, it is assumed that tasks B and C are in some waiting state and task A is executed to acquire the computer resource X. Then, the wait for task B is released, and (task B
Is higher in priority than task A), execution of task A is interrupted, and task B is in the execution state. further,
It is assumed that the waiting of the task C is released, the execution of the task B is interrupted, and the task C is in the execution state. Task C is
An attempt is made to acquire the computer resource X during the execution, but since the computer resource X is being used by the task A, the computer resource X waits and the execution of the task B is restarted. Figure 9
This state is illustrated.

In such a situation, the task C with the highest priority is executed because the central processing unit (CPU) is abandoned because the task B waits and the execution of the task A is resumed. Then, the task A is delayed until it returns the computer resource X.

In this way, originally, the execution of a task with a high priority is interrupted by a task with a low priority due to waiting for acquisition of computer resources, etc. Inversion (priority i
n version). Such a situation also occurs for execution of a program portion (critical region) that must be executed exclusively (a plurality of programs cannot be executed at the same time). The inversion of the priority may delay the execution of the task that should be preferentially processed, which may significantly reduce the processing capacity of the system (processing capacity per unit time regarding the processing that the task A should perform). is there.

One of the proposed solutions to the above-mentioned problem of priority inversion is priority inheritance (priorit).
y inheritance). In the example above,
It is the same that task C enters the waiting state for computer resources when task C enters the execution state and attempts to acquire computer resources X, but the operating system temporarily assigns the priority of task A to the tasks. It is possible to prevent the delay of the execution of task C due to the execution of task B by increasing the priority of C and executing task A with priority. When the task A returns the computer resource, the operating system restores the priority of the task A and resumes the execution of the task C. FIG. 10 illustrates this state. As compared with FIG. 9, the delay time of execution of task C by task B is shortened.

[0008]

In the conventional priority processing method described above, task A can automatically raise the priority by the operating system.
It is not necessary to program while paying attention to the above-mentioned priority inversion problem. However, on the other hand, as a result,
Originally, a task with a low priority is prioritized and executed, which is not preferable from the viewpoint of the entire system. Especially, when task A is prioritized and executed for a long time, like task B, There is a problem that it becomes difficult to execute a task having a higher priority than the task A. In order to avoid this problem, if the computer resource return processing of task A is performed in detail, the overhead due to the computer resource acquisition / return processing increases.

It is also conceivable that when the task C tries to acquire the computer resource, the task A can actually return the computer resource and the task C can be executed promptly. In such a case, not only when the resource acquired by the task A is not being used at that time, but for example, the task A abandons the current process and returns the computer resource (task C It also includes the case where the processing is re-executed from a predetermined location after the execution of (1) is completed and the computer resources returned again are acquired.
The conventional priority processing method described above has a drawback that it cannot cope with such a case.

The present invention solves such a problem, and a computer resource acquired by one task A is transferred to another task B.
If the priority of task B is higher than the priority of task A, the software exception handling routine defined by task A is activated to minimize the delay in the execution of the high priority task. An object is to provide a device that can be suppressed.

[0011]

According to the present invention, an input / output device, a storage device, and a computer resource are connected to a central processing unit, and the central processing unit has priority acquisition means for acquiring the priority of a task. Priority comparison means for comparing the priorities of the tasks acquired by the priority acquisition means, computer resource acquisition means for acquiring the computer resources when executing the tasks, and computer resources for returning the computer resources after executing the tasks In a multi-task computer having a return means and a task identification means for identifying the task that has acquired the computer resource, an exception handling routine defining means for defining a software exception handling routine of the task in the central processing unit, and a definition Control means for executing task control in the storage device, which comprises: A task control block for storing a context save area for saving the context,
An exception context save area for saving the exception context is included.

[0012]

When a task tries to acquire a certain computer resource, it is determined whether the computer resource is in use, and if not, the task is assigned and processed. When used by other tasks, the priorities of the two are compared, and if the priority of the task to be used is the same as or lower than the priority of the task being used, the task to be used To wait. When the priority of the task to be used is high, the priority of the task in use is saved, and the priority of the task in use is increased to the priority of the task to be used.

Next, it is judged whether or not the exception handling routine of the task in use is defined in advance. If it is defined, the context of the task in use is saved,
Start the exception handling routine. If it is not defined, the task to be used is placed in the computer wait state without performing any processing.

As a result, it is possible to minimize the delay in the execution of the high priority task.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment of the present invention.

In the embodiment of the present invention, an input / output device 2, a storage device 3 and a computer resource 4 are connected to a central processing unit 1,
In the central processing unit 1, a priority acquisition unit 11 that acquires the priority of a task, a priority comparison unit 12 that compares the priority of the task acquired by this priority acquisition unit, and a computer resource when executing the task. 4, a computer resource acquisition unit 13 that acquires the computer resource 4, a computer resource return unit 14 that returns the computer resource 4 after executing the task, and a task identification unit 15 that identifies the task that has acquired the computer resource 4. Characteristically, the central processing unit 1 is provided with an exception handling routine defining means 16 for defining a software exception handling routine of a task, and an exception handling routine starting means 17 for launching the defined exception handling routine, and the storage device 3 A task control block 201 that stores control information for performing task control, a context save area 208 that saves a context, And a exception for context save area 210 for saving the external context.

FIG. 2 is a block diagram showing the configuration of the task control block in the embodiment of the present invention.

The task control block 201 includes a priority 202 indicating the priority of a task, a priority save area 203 for temporarily saving the task priority, and a context save area address for holding the addresses of the context save area 208. 204, an exception handling routine address 205 that holds the defined exception handling routine, an exception context saving area address 206 that holds the address of the exception context saving area 210, and other information necessary for task control, such as a task It holds control information 207 such as the state of.

The context save area 208 is a data structure for saving the original context when the exception handling routine is activated, and the save area 209 is an area for holding the actual context. Exception save area 2
Reference numeral 10 is a data structure for saving the context when the exception handling routine is executed, and the exception save area 211 is an area for holding the context of the actual exception handling routine.

Next, the operation of the embodiment of the present invention thus constructed will be described. 3 is a flowchart showing the flow of resource acquisition processing in the embodiment of the present invention, FIG. 4 is a flowchart showing the flow of resource return processing in the embodiment of the present invention and the conventional example, and FIG. 5 is exception processing in the embodiment of the present invention and the conventional example. It is a flowchart which shows the flow of the termination process of a routine.

First, the resource acquisition process will be described with reference to FIG. Processing in the case where an exception handling routine is defined is added to the processing in the conventional operating system shown in FIG. For example, when the task C tries to acquire the computer resource X, if the computer resource is not in use, the task C is allocated with the computer resource and the processing ends.

When the computer resource is in use (by task A), the priorities of task C and task A are compared. If the priority of task C is equal to or lower than the priority of task A,
The task C is placed in a computer resource waiting state and the processing is terminated. If the priority of task C is high, the priority of task A is saved and the priority of task A is increased to the priority of task C.

Then, it is judged whether or not the exception handling routine of task A is defined. If it is defined, the context of task A is saved and the exception handling routine of task A is started. If not defined,
The task C is put in the computer resource waiting state without any processing, and the processing is terminated.

The priority of the task A raised by this resource acquisition processing is the same as in the conventional operating system.
It is restored by the process of returning computer resources. That is, as shown in FIG. 4, the process of returning the computer resource of the task A is performed, it is determined whether there is a computer resource waiting task, and if there is no task, the process ends. If there is, the wait for task C is released, and it is determined whether or not there is a priority saved. If there is no priority, the process is terminated, and if there is a priority, the priority of task A is restored.

In the exception handling routine, task A returns computer resources and restores the saved context as shown in FIG. 5 so that task C can be executed quickly. Needless to say, when the exception handling routine is not defined, the operation is exactly the same as the conventional one.

FIG. 6 is a diagram showing an example of improvement of priority inversion in the embodiment of the present invention.

[0027]

As described above, according to the present invention, when another task B attempts to acquire a computer resource acquired by a task A, the priority of the task B is higher than the priority of the task A. If the value is higher, the software exception handling routine defined by task A is started, and the operating system controls the priority task to execute the lower priority task according to the priority inheritance, thereby executing the higher priority task. This has the effect of minimizing the delay.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a task control block according to the embodiment of the present invention.

FIG. 3 is a flowchart showing a flow of resource acquisition processing in the embodiment of the present invention.

FIG. 4 is a flowchart showing the flow of resource return processing in the embodiment of the present invention and the conventional example.

FIG. 5 is a flowchart showing a flow of termination processing of an exception processing routine in the embodiment of the present invention and the conventional example.

FIG. 6 is a diagram showing an example of improvement of priority inversion according to the embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a task control block in a conventional example.

FIG. 8 is a flowchart showing a flow of resource acquisition processing in a conventional example.

FIG. 9 is a diagram showing an example of priority inversion in a conventional example.

FIG. 10 is a diagram showing an example of improvement of priority inversion due to priority inheritance in the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 central processing unit 2 input / output device 3 storage device 4 computer resource 11 priority acquisition means 12 priority comparison means 13 computer resource acquisition means 14 computer resource return means 15 task identification means 16 exception processing routine definition means 17 exception processing routine activation means 201, 701 Task control block 202, 702 Priority 203, 703 Priority save area 204, 704 Context save area address 205 Exception handling routine address 206 Exception context save area address 207, 707 Other task control information 208, 708 Context Save area 209, 709 Save area 210 Exception context save area 211 Exception save area

Claims (1)

[Claims] 1. A central processing unit, an input / output device, a storage device,
And a computer resource are connected to the central processing unit, and a priority acquisition unit that acquires the priority of the task, a priority comparison unit that compares the priorities of the tasks acquired by the priority acquisition unit, and execute the task Multitask calculation including computer resource acquisition means for acquiring the computer resource when executing, computer resource return means for returning the computer resource after task execution, and task identification means for identifying the task that acquired the computer resource In the device, the central processing unit is provided with an exception handling routine defining unit that defines a software exception handling routine of a task, and an exception handling routine starting unit that launches the defined exception handling routine, and the storage unit includes a task control unit. Control block that stores the control information for performing the task and the context that saves the context And 避領 zone, multitasking computing device which comprises a exceptions for context save area for saving the exception for context.