JPH05113891A - Pseudo semaphore system - Google Patents

Abstract

(57) [Summary] [Object] An object of the present invention is to realize a simple multi-task operating system capable of exclusive control of a plurality of tasks. [Structure] The pseudo semaphore management table is provided with a flag indicating whether or not a pseudo semaphore is used for each pseudo semaphore number and a link terminal. In this link terminal, the event number (task number) of the task waiting for the event with the flag of the corresponding pseudo semaphore being "1" is sequentially stored. If the task that owns the pseudo semaphore releases the resource,
The flag of the corresponding pseudo semaphore number in the pseudo semaphore management table is reset to "0". When the flag is reset, the event with the event flag number registered at the head of the queue of the link terminal is notified of the event occurrence. The task notified of the event occurrence is set to the execution state by performing the TEST & SET of the flag and setting the flag to "1".

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a simple multitasking operating system for a personal computer or the like.

[0002]

2. Description of the Related Art In a system capable of executing a plurality of tasks in parallel, it may be inconvenient if a plurality of tasks access the same resource at the same time. Therefore, one task is assigned to a critical section for a particular resource. When it is entered, it must be managed so that another task cannot access the resource. As a method of managing such a task, there is a method using a semaphore.

Further, in a system having no semaphore, for example, a resource-in-use flag is provided, and if the resource-in-use flag is off, the flag is turned on to put the task in the execution state, and the resource-in-use flag is on. If so, there is a method of monitoring the resource busy flag in a loop or at regular intervals and waiting for the flag to turn off. There is also a method of associating a resource-in-use flag with an event flag and waiting for resource release.

[0004]

In the method of monitoring the resource-in-use flag by using a loop, the CPU is used while the task does nothing while the loop is being executed. There is a problem that the processing efficiency of the processing is reduced. Further, in the method of monitoring the resource-in-use flag at regular intervals, even if the resource becomes available, the resource cannot be used until the monitoring program is activated and it is detected that the flag is off. There was a point.

Further, in the method in which the resource in-use flag is made to correspond to the event flag to wait for the release of the resource, the above problem can be solved, but the task waiting for the event is limited to one task, and only the exclusive control of two tasks is performed at the same time. There was a problem that it could not be done.

An object of the present invention is to realize a simple multitasking operating system capable of exclusive control of a plurality of tasks.

[0007]

FIG. 1 illustrates the principle of the present invention. In the figure, the pseudo semaphore management table 1 comprises a flag indicating whether or not each pseudo semaphore is in use for each pseudo semaphore code and a queue terminal.

When setting the pseudo semaphore, the test & set means 2 determines whether or not the flag of the pseudo semaphore management table 1 is set, and when the flag is not set, sets the flag.

The first task management means 3 uses the test &
When it is determined by the setting means 2 that the flag is set, the event flag code of the current task (calling task) is linked to the end of the queue of the corresponding queue terminal, and the task is placed in the event wait state. ..

When resetting the pseudo semaphore, the reset means 4 resets the flag of the corresponding pseudo semaphore code in the pseudo semaphore management table. Second
Task management means 5 checks whether or not there is a queue in the queue terminal of the corresponding pseudo semaphore code, and when there is a queue, deletes the eventflag code at the head of the queue terminal, Notify the task corresponding to the event flag code that an event has occurred.

[0011]

According to the present invention, when the flag of the corresponding pseudo semaphore code in the pseudo semaphore management table 1 is set when the task requests the pseudo semaphore,
Event flag codes of requested tasks are sequentially registered in the queue of the pseudo semaphore management table 1, and those tasks enter the event wait state. Then, when the task that owned the pseudo semaphore resets the flag, the occurrence of the event is notified to the task with the eventflag code at the head of the corresponding queue.

That is, by performing task management by the pseudo semaphore method as described above, it is possible to provide an operating system having no multitask function with a multitask function equivalent to a multitask operating system using a semaphore. ..

[0013]

Embodiments of the present invention will be described below with reference to the drawings. The pseudo semaphore method of the present invention, in an operating system without a multitask function,
This is to realize a multitasking function equivalent to a multitasking operating system having a semaphore.

FIG. 2 is a flow chart of the pseudo semaphore SET function in the pseudo semaphore system of the embodiment. When a task uses a resource shared by a plurality of tasks, the pseudo semaphore SET function of FIG. 2 is called. In this pseudo semaphore SET function processing, first, in step S1, the pseudo semaphore management table is searched to read the flag corresponding to the pseudo semaphore number, and if the flag is "0", set "1" (this is TES).
Called T & SET).

FIG. 3 is a diagram showing the structure of the pseudo semaphore management table, in which each pseudo semaphore number is provided with a flag indicating whether the pseudo semaphore is used and a link terminal.

The pseudo semaphore number is determined corresponding to the resource, and the pseudo semaphore number is determined depending on which resource the task uses. In the link terminal, the event flag number (task number) of the task waiting for the event with the corresponding pseudo semaphore flag being "1"
Are stored in sequence, and when the flag of the pseudo semaphore is reset, the occurrence of events is notified in order from the task with the eventflag number at the head of the queue. Therefore,
The length of the queue of the link terminal is the length of the multiplicity of tasks that request the corresponding pseudo semaphore.

In the pseudo semaphore method of the present embodiment, it is sufficient to have a flag indicating whether the pseudo semaphore is used as the pseudo semaphore management table and the event flag number of the task waiting for the event. A small amount of information to manage is required. Furthermore, it is possible to realize almost the same multitask function with a smaller amount of programs compared to the multitask operating system using semaphores.

If the flag corresponding to the pseudo semaphore number is "0" in the determination of step S1 in FIG. 2, the flag is set to "1" to put the calling task in the execution state. On the other hand, if the flag is "1" in the determination in step S1, another task is using the resource, so the task number (current task number) of the calling source task is obtained as the event flag number in the next step S2. .. And
In step S3, the above event flag number is linked to the end of the queue of the link terminal having the corresponding pseudo semaphore number. As a result, the task number of the calling source task this time is registered in the queue as an event flag number, and the task enters the event wait state.

Next, the operation when the task possessing the pseudo semaphore releases the resource will be described with reference to the flow chart of the pseudo semaphore RESET function in FIG. When the task releases resources, it calls the pseudo semaphore RESET function of FIG. Pseudo Semaphore RE
In the SET function processing, first, the flag of the pseudo semaphore number corresponding to the resource used by the task is reset to "0" in step S5 of FIG. Then, step S6
Search the pseudo semaphore management table with to see if there is a queue at the link terminal.

If a queue exists in the link terminal, the eventflag number at the head of the queue is deleted in step S7, and the event of this eventflag number is generated.

FIG. 5 shows the pseudo semaphore management table at this time. When the flag of the pseudo semaphore is reset, the event number of the task i at the head of the queue is deleted and the event is issued to the task i. Is notified. As a result, the task i is changed from the event wait state to the ready state, and the task j in the second queue is changed to the head of the queue.

When the event occurrence is notified, the task i calls the above-mentioned pseudo semaphore SET function to perform TEST & SET of the flag of the corresponding pseudo semaphore number. At this time, the flag of the corresponding pseudo semaphore is "0".
Therefore, task i is set to the execution state by setting "1" in the flag.

As described above, in the above embodiment, when the pseudo semaphore requested by the task is used, the event flag numbers are sequentially registered in the link terminal of the corresponding pseudo semaphore number in the pseudo semaphore management table, and the task Is set to the event waiting state. Then, when the flag of the pseudo semaphore is reset, the event occurrence is notified in order from the head event flag number registered in the link terminal.

As described above, the pseudo semaphore management table is provided, and each task sets or resets the corresponding flag in the pseudo semaphore management table, whereby exclusive control of a plurality of tasks (an arbitrary number of 2 or more) becomes possible. So
It is possible to provide an operating system that does not have a multitask function with a multitask function that is almost the same as an operating system that realizes multitask using semaphores.

[0025]

According to the present invention, by providing a pseudo semaphore management table consisting of a flag corresponding to a pseudo semaphore code and a queue, exclusive control of a plurality of tasks becomes possible, and a plurality of tasks can be executed in parallel in real time. Can be processed.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a flowchart of a pseudo semaphore SET function according to the embodiment.

FIG. 3 is a diagram showing a configuration of a pseudo semaphore management table at the time of TEST & SET.

FIG. 4 is a flowchart of a pseudo semaphore RESET function according to the embodiment.

FIG. 5 is a diagram showing a configuration of a pseudo semaphore management table at the time of RESET.

[Explanation of symbols]

 1 Pseudo Semaphore Management Table 2 Test & Set Means 3 First Task Management Means 4 Reset Means 5 Second Task Management Means

Claims (1)

[Claims] 1. A pseudo semaphore management table (1) consisting of a flag corresponding to a pseudo semaphore code and a queue terminal; When it is determined that the flag is set by this test & set means (2), which determines whether or not it is set, and sets the flag when the flag is not set Linking the event flag code of the current task to the end of the queue of the corresponding queue terminal and putting the task in the event wait state
Task management means (3) and reset means for resetting the pseudo semaphore code flag of the pseudo semaphore management table (1) when resetting the pseudo semaphore
(4) and the semaphore management table (1) of the corresponding pseudo semaphore code Queue Check whether or not there is a queue at the terminal, and if there is a queue, the event flag code at the head of the queue And a second task management means (5) for notifying the task corresponding to the event flag code of the occurrence of an event, and a pseudo semaphore system.