JPH0556539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information processing device that performs multitasking, and particularly to a method for implementing an operating system.

[Conventional technology]

Multitasking is achieved by dividing a program into multiple tasks and executing each task in a time-sharing manner in order to improve the processing efficiency of the entire system. Normally, this is a basic function of the operating system, and tasks may be switched when each task issues a processing request (hereinafter referred to as a system call) to the operating system, or due to an interrupt.
In a multitasking execution environment, each task generally takes a running state, an executable state, and a waiting state as shown in FIG. 4, and these states are controlled by the operating system. A running state is the only one that exists at a time and occupies the central processing unit. The executable state is a state in which all the conditions for execution are met but the state cannot be executed due to priority, and the wait state is a state in which the state is waiting for processing by another task, waiting for a message from another task, etc. This is a state in which the transition to the executable state is not possible due to some reason. The status of each task changes due to system calls, external interrupts (hereinafter collectively referred to as events), and multitasking is realized. FIG. 5 is a diagram showing the relationship between interrupt processing and system calls, and the numbers in the diagram indicate processing procedures. While task A is running, an interrupt occurs at INT point 1, and control shifts to interrupt processing 2. During the interrupt processing 2, data is collected and a system call is sent as a message.
When a message is sent using SYS1, the operating system receives the message once sent, and if there is a task waiting to receive a message, it makes that task executable and then assigns it the highest priority. Select a high task and put it into execution state. In this example, if task B is in a message waiting state and has a higher priority than task A, control is transferred to task B by executing system call SYS1, and processing 3 is executed.
After execution, the operating system executes end processing for task B using system call SYS2, and then passes control to continuation processing 4 of the interrupt processing. Processing 4
Then, after continuing the processing to be executed in the interrupt processing, a system call RETI is issued to request a return from the interrupt processing, and the interrupt processing is ended. The operating system returns control to the interrupted location, and task A executes continuation processing 5. In this way, when a system call that causes a task state transition is issued during interrupt processing, the processing flow as described above is generally followed.

[Problem that the invention seeks to solve]

As mentioned above, in a normal operating system, depending on the type of system call issued during interrupt processing as shown in Figure 5, it may induce a task state transition; If a system call is issued during interrupt processing, a part of the interrupt processing that is originally urgent (continuation processing 4 in the case of Figure 5) will be affected by the priority and task status of task A that received the interrupt. However, this method has the disadvantage that the processing may be postponed. In particular, as in this example, simply by sending a message, there are many problems if control is transferred to another device when processing needs to be continued. In addition, to avoid this drawback, as shown in Figure 6, even if an event that causes a task state transition occurs in system call SYS1 during interrupt processing, it is suspended, processing 3 continues, and the interrupt is processed. In order to accept an event by executing the RETI system call that exits the interrupt processing, write a software flag at the beginning of the interrupt processing to indicate that the interrupt is in progress.
A method must be used in which the operating system determines the flag during system call processing and performs software processing such as temporarily suspending task state transitions.Both the application program and the operating system are software-based. It has the disadvantage of being too burdensome to process. Alternatively, in order to avoid such complicated processing, some systems place limits on the system calls that can be used during interrupt processing, and prohibit the occurrence of events that cause task state transitions during interrupt processing. However, the problem is that the system configuration lacks flexibility.

[Means for solving problems]

The present invention provides a first means for determining whether an interrupt is being processed or not, and a system call issued from the first means in a processing device that realizes multitasking. A second means for suspending a part of the processing and retaining the suspension information is provided, and the second means is determined by executing a system call indicating the end of the interrupt processing, and the suspension is executed according to the suspension information. It is characterized by processing.

〔Example〕

The present invention will be explained with reference to the drawings.

FIG. 1 is a hardware configuration diagram according to an embodiment of the present invention. The interrupt control unit 1 detects internal and external interrupts, determines the priority order, and then accepts the interrupts as interrupts. The interrupt determination unit 4 processes the interrupt from the time the interrupt control unit 1 accepts the interrupt until the system call to end the interrupt processing is issued to the operating system.
Holds information indicating that it is an interrupt process. The system call execution unit 3 is a part for actually executing each system call. System call determination section 2 generates signals to system call execution section 3 in response to various system calls. The event suspension control unit 6 receives activation from the system call execution unit 3,
A process of writing necessary information into the pending information register 5 is performed. The specific processing procedure is shown below. Figure 2 shows the system call during interrupt processing in Figure 6.
This figure shows the processing of the operating system when SYS1 is for sending a message to the operating system. In processing, the operating system receives the message once, and if there is a task waiting for a message, sends the message. Thereafter, the state of the interrupt determination section is detected, and if no interruption is occurring, a transition of the task state is caused, but if no interruption is occurring, control is passed to the event suspension control section 6. The event suspension control unit 6 writes the type of event into the suspension information register 5 according to the type of event. Since the type of event is only memorized and no processing is performed, it is possible to immediately proceed to the execution of process 3 in FIG. 6 without causing a transition of the task state. FIG. 3 shows the processing of the system call RETI for returning from an interrupt. In the RETI process, the contents of the pending information register 5 shown in FIG. 1 are determined, and if there is no pending information, the interrupt determining section 4 is cleared and a return process from the normal interrupt processing routine is performed. If there is pending information, processing is performed according to the contents of the pending information register 5 to cause a task state transition, and one of the tasks in the executable state is selected and brought into the running state. Thereafter, after clearing the interrupt determination section 4, the process returns from the interrupt processing. Therefore, the task state changes only when a system call is executed to return from interrupt processing, and control is transferred to task B, which executes process 4, as shown in FIG.

〔Effect of the invention〕

As explained above, the present invention uses hardware to realize means for identifying whether or not an interrupt is occurring, and means for suspending the occurrence of an event.
Interrupt processing can be written without being aware of the state of the task at the time of the interrupt, and system calls can be written within interrupt processing without being aware of whether or not a state transition will occur. The installation cost of the Yong program will be significantly improved. Furthermore, it can be realized with simple hardware and is fully compatible with LSI applications such as microcomputers. In addition, the design of an operating system is simplified by using the mechanism of the present invention, and the reduction in reliability caused by the complexity of processing and the burden on application programs that would otherwise occur when relying only on software processing can be avoided. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a hardware configuration according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Interrupt control unit, 2... System call determination unit, 3... System call execution unit, 4... Interrupt determination unit, 5... Pending information register, 6... Event pending control unit, FIG. is a system call processing flow diagram for message transmission. FIG. 3 is a flowchart of a system call process for returning from an interrupt. FIG. 4 is a task state transition diagram, FIG. 5 is a diagram showing the relationship between interrupt processing and system calls in the conventional example, and FIG. 6 is a diagram showing the relationship between interrupt processing and system calls in the present embodiment. be.

Claims (1)

[Claims] 1. In a multitasking type information processing device that allocates tasks in a time-sharing manner to perform processing, the system call execution unit executes a system call that is a processing request to an operating system from the task, and the system call execution unit An interrupt determination unit that determines whether a task is being processed or an interrupt is being processed, and when processing a system call issued during interrupt processing, the interrupt determination unit can be referenced to determine whether the interrupt is being processed. and an event suspension control section that receives activation from the system call execution section and writes to the suspension information register, and the interrupt determination section and , the information register and the event suspension control section are provided independently of the system call execution section, and the suspension information register is determined by executing a processing request to an operating system indicating the end of interrupt processing; An information processing device that performs processing according to information held in the pending information register.