JPH08202566A - Inter-processor communication system - Google Patents

Abstract

PURPOSE: To smoothly perform an inter-process communication by preventing deadlock at the time of a data rush. CONSTITUTION: When a queue buffer is full, message data by a transmission task are temporarily stored on an external storage device in FIFO basis and when the queue buffer has a vacancy, the message data on the external storage device are taken out on the FIFO basis and sent to the queue buffer. Therefore, even when the queue buffer is full, the transmission task stores the message data to be sent on the external storage device without waiting for the queue buffer to have a vacancy, and can end its processing; and the process never stops in the wait state of message data transmission and the deadlock and the destruction of an OS function can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interprocess communication system for communicating message data between processes via a queue buffer.

[0002]

2. Description of the Related Art Conventionally, for example, a computer such as a general workstation equipped with an OS (operating system) in a multitasking environment and a CPU, a parallel processing mechanism for input / output operations, an interrupt mechanism, a memory protection mechanism, etc. In, an independent virtual space and virtual CPU (task) are assigned to each process. For example, when performing parallel processing by providing a plurality of execution flows in one program, such as when performing data processing in parallel during terminal display processing, a process is generated for each parallel processing, and each process is generated. Processing proceeds while sharing data between them.
At that time, since the virtual space of each process is independently allocated, in order to share data between processes, for example, a method of exchanging message data between processes or a shared memory that shares memory between processes is used. Various inter-process communication such as a method, a method of performing communication using a predetermined file among a plurality of processes, and the like are performed.

Here, a process configuration diagram of inter-process communication using a message is shown in FIG. Further, FIG. 13 shows an example of the flow of message communication performed between a plurality of processes.
Shown in Each process contains a send task and a receive task,
As shown in FIG. 12, the send task temporarily stores the message data to be sent to another process via the OS in the queue buffer on the memory set by the OS. The reception task receives the storage contents of the queue buffer via the OS. Thus, via the queue buffer managed by the OS, for example, as shown in FIG.
Communicate between processes using messages.

[0004]

However, in a system for performing message communication between processes by using the queue buffer set by the OS as described above, the communication volume between a plurality of processes increases and the queue buffer becomes full. If the queue buffer becomes full, the system will be seriously adversely affected. For example, when the processing procedure of the process Y shown in FIG. 13 is as shown in FIG. 14, the process Y receives a certain message data from the process X,
The message data is transmitted to the process Z after a predetermined process is performed. If the queue buffer is full at the time of transmitting the message data, the process waits for transmission and the process of the process Y is stopped. Further, if the process Z is in the reception waiting state until the message data is transmitted by the process Y, the queue buffer becomes empty, and the process Y is stored in the queue buffer.
The process Z enters the reception waiting state until the message data is received. If the queue buffer becomes full, such a transmission waiting state and a reception waiting state occur simultaneously in a plurality of processes, and a so-called deadlock state occurs in which the processes of the plurality of processes wait for the processes of other processes, resulting in a OS. Function becomes abnormal. For example, in a system in which a plurality of terminal devices are connected to a monitoring control device via a LAN, the information transmitted from each terminal device is read, and the monitoring control device centrally monitors and controls the state of each terminal device. In this case, if the status of each terminal changes all at once, such as when the commercial power supply that is the power source of each terminal device fails, the data of the status change of each terminal device (such as data indicating a power failure) is displayed. Transmission to the supervisory controller causes a sudden increase in the communication volume of a plurality of inter-process communications per unit time (hereinafter referred to as “data rush”) within the supervisory controller, and the queue buffer may become full. there were.

The function of inter-process communication by the message is performed by a communication system supported by UNIX System V, for example, but it is necessary to set the number (capacity) of queue buffers first because of the structure of the OS. Is set by the user in consideration of the amount of message data that can occur at the same time. However, as mentioned above, the communication volume per unit time of inter-process communication may increase rapidly in a short time, and if all the possible volumes are set correspondingly, a huge memory area is required. Next to it is unrealistic. Usually, an appropriate value is set in consideration of the occurrence frequency of data rush with respect to the processing capacity of the CPU, but it is not fixed according to the change in the amount of the program with respect to the processing capacity of the CPU. Even if the number of queue buffers is set with a margin, it is difficult to judge whether or not the number of queue buffers has a margin.

An object of the present invention is to provide an inter-process communication system which solves the above-mentioned problem by allowing a transmitting task to end its processing immediately without waiting even if the queue buffer is full. To do.

[0007]

According to the present invention, a send task included in a process sends message data to a queue buffer, and a receive task included in a process receives message data from the queue buffer. In a system for performing message communication between processes, as described in claim 1, when the queue buffer is full, the message data from the send task is externalized so that the send task does not wait even when the queue buffer is full. Message data external storage means for temporarily storing in the storage device in the first-in first-out format, and external storage device message data transmission means for taking out the message data in the external storage device in the first-in first-out format and transmitting it to the queue buffer when the queue buffer has a space. To provide.

Further, according to the present invention, in order to transmit the message data stored in the external storage device to the queue buffer independently of the transmission task, as described in claim 2, the message data is stored in the queue buffer. Without
Further, when the queue buffer has a free space, the receiving task is provided with means for taking out the message data stored in the external storage device in the first-in first-out format and transmitting it to the queue buffer.

Here, an example of the process configuration of the present invention is shown in FIG. Fig. 1 shows one interprocess communication
Only the configuration for one send task and one receive task is shown. In the inter-process communication system according to claim 1, in FIG. 1, when the transmission task transmits message data to the queue buffer, when the queue buffer is full, the message data by the transmission task is stored in the external storage device in a first-in first-out format. When the queue buffer is temporarily stored and there is a space in the queue buffer, the message data already stored in the external storage device is transmitted to the queue buffer. Further, in the interprocess communication system according to claim 2, when there is no message data in the queue buffer and there is a space in the queue buffer, the receiving task retrieves the message data stored in the external storage device in the first-in first-out format, Send to buffer.

[0010]

In the interprocess communication system according to claim 1 of the present invention, the message data external storage means temporarily stores the message data by the transmission task in the external storage device in the first-in first-out format when the queue buffer is full, and the external storage When the queue buffer has a free space, the device message data transmitting means extracts the message data in the external storage device in the first-in first-out format, that is, the message data stored first and transmits it to the queue buffer. Therefore, even when the queue buffer is full,
The sending task does not wait for the queue buffer to become empty,
The message data to be transmitted can be stored in the external storage device, and the processing as the transmission task can be ended.
Therefore, as described above, the process does not stop in the waiting state for message data transmission, and the above-mentioned deadlock and destruction of the OS function are prevented.

In the interprocess communication system according to claim 2, when the receiving task receives the message data from the queue buffer, when there is no message data to be received in the queue buffer and there is a space in the queue buffer,
The message data stored in the external storage device is taken out in the first-in first-out format, that is, the message data stored first is taken out and transmitted to the queue buffer. As a result, the message data stored in the external storage device is transmitted to the empty queue buffer during the message data reception waiting time in the reception task, and the processing efficiency of message communication is improved.

[0012]

FIG. 2 is a block diagram showing the configuration of a supervisory control system to which an interprocess communication system according to an embodiment of the present invention is applied. In this example, a monitoring control system is configured by connecting a monitoring control device and a plurality of terminal devices via a LAN, respectively, and the monitoring control device receives data representing various states from the plurality of terminal devices and Control data is transmitted to the device.

Next, FIG. 3 is a block diagram showing the configuration of the supervisory control device shown in FIG. In FIG. 3, the CPU 1 executes the program previously written in the ROM 2 and the program loaded from the hard disk drive device 5 or the floppy disk drive device 7 into the RAM 3. Further, the RAM 3 uses a part thereof as a queue buffer at the time of interprocess communication. The hard disk drive device 5 is an external storage device according to the present invention, and the hard disk controller 4 controls reading and writing of data.
The floppy disk drive device 7 is used for loading and saving programs and data, and the floppy disk controller 6 controls the floppy disk drive device 7. The CRT 9 is used to display the status of each terminal device, and the CRT controller 8 controls the display. LAN controller 10
Performs data transmission control with a plurality of terminal devices via the LAN.

Next, FIG. 4 shows a basic structure of a main part in the hard disk drive device 5 shown in FIG. FIG. 4 shows only the data structure used by one transmission task in one interprocess communication. In FIG. 4, a "buffer area" is an area for storing a plurality of message data, and a sufficient area is secured in advance. The "message number counter" is an area for storing the current number of message data stored in the buffer area, the "write pointer" is a data storage area for indicating the position where message data should be written next time in the buffer area, and "readout". The "pointer" is a data storage area indicating a storage location of message data to be read next time from the buffer area. Such a data structure is provided for each transmission task, and message data is written to and read from the buffer area in a first-in first-out format using these data storage areas.

FIG. 5 is a diagram showing an example of the flow of message data by various processes in the monitoring control device. In FIG. 5, the communication control circuit reads the data transmitted from the terminal device via the LAN. The monitoring process reads the data received by the communication control circuit via the communication driver, and sends respective message data to the display process and the failure management process. These message data are once written in the queue buffer. The display process receives the message data sent to the queue buffer by the monitoring process, generates data to be displayed, and outputs the data to the display driver. The display driver thereby generates the display signal for the CRT. The failure management process receives the message data sent from the monitoring process, performs a predetermined process, and sends the message data to another process.

FIG. 6 is a flow chart showing the processing procedure of the monitoring process shown in FIG. First, it waits for reception from the communication driver, and if it is failure data from the communication driver (data transmitted from the terminal device when the terminal device detects some failure), that data is used as message data and failure for the display process. Send as message data for management process. (N1 → n2
→ n3 → n4 → n5). If you receive normal state change data from the communication driver instead of failure data,
The message data of the state change is transmitted as message data for the display process and the failure management process (n6 → n7).

FIG. 7 is a flowchart showing the processing procedure of the display process. First, the message data transmitted from the monitoring process and stored in the queue buffer is received, and the failure status or status change of the terminal is displayed (n1
1 → n12 → n13). Then, another process is performed and a series of display processes are repeated.

FIG. 8 is a flowchart showing the procedure of the failure management process. First, the message data transmitted from the monitoring process and stored in the queue buffer is received, and the failure management processing is performed according to the data (n21 →
n22 → n23). Then, another process is performed and a series of display processes are repeated.

Next, in steps n4, n5 and FIG.
The procedure of the transmission tasks shown in n6 and n7 is shown in FIG. First, the presence / absence of message data (hereinafter referred to as “disk data”) stored in a hard disk drive which is an external storage device is checked, and if there is no disk data, the message data to be sent this time is sent (n31 → n32 →
n33). At that time, if the queue buffer is not full,
The processing of the transmission task ends as it is. Step n33
If the OS returns an error indicating that the queue buffer is full, the message data this time is written to the hard disk as new disk data (n
34 → n35). Also, if the disk data is checked, and if the disk data already exists, the message data to be sent this time is additionally written to the hard disk (after writing in the first-in first-out format), and then the later-described disk data transmission processing is performed. (N36 → n3
7). The steps n35 and n36 correspond to "message data external storage means" according to the present invention, and step n37 corresponds to "external storage device message data transmission means" according to the present invention.

As described above, even if the queue buffer is full, the sending task ends immediately by writing the message data to the hard disk. Therefore, the sending task does not wait and the process at the time of data rush does not occur. It is possible to avoid deadlock due to stoppage.

FIG. 10 is a flow chart showing the procedure of the disk data transmission process of step n37 in FIG. First, the presence / absence of disk data is checked, and if there is disk data, the oldest data (first inserted data) of the disk data is transmitted. At this time, if the OS does not return the error that the queue buffer is full, the disk data is checked again. By repeating this process, the message data is transmitted to the queue buffer in order from the oldest disk data. This process ends when all the disk data is sent to the queue buffer or when the queue buffer becomes full.

FIG. 11 is a flow chart showing the procedure of the receiving task in steps n11 and n21 shown in FIGS. 7 and 8. First, data reception without WAIT is performed (n41). If, by chance, there is message data in the queue buffer at this timing, the message data is read and this reception task ends (n41 → n42 →
END). If there is no received data, the disk data transmission process is performed using this time without waiting for message data to enter the queue buffer (n4
3). This processing is the same as the processing shown in FIG. 10, and this step n43 corresponds to the means according to claim 2 of the present invention. After that, if the disk data still exists, the data reception without WAIT is performed again at this point,
If there is no received data, the process returns to step n43 (n
44 → n45 → n46 → n43). By repeating this process and sequentially transmitting the disk data to the queue buffer, if the disk data is exhausted, data reception with WAIT is performed. That is, it waits until message data is entered in the queue buffer, and if message data is entered, it is received (n47). Step n45 or n
The data is received at 47, and if no reception error is returned from the OS at that time, the process is terminated. If a reception error occurs, the error is displayed (n48 → n4
9).

As described above, even in the receiving task, the disk data is transmitted to the queue buffer when there is no message data in the queue buffer and there is a space in the queue buffer. , Disk data can be efficiently transferred to the queue buffer.

[0024]

According to the interprocess communication system according to the first aspect of the present invention, even when the queue buffer is full, the transmission task does not wait for the queue buffer to become empty and externally stores the message data to be transmitted. You can store it in the device and finish the process as a transmission task.
The process does not stop in the waiting state for sending the message data, and the deadlock and the destruction of the OS function are prevented.

According to the interprocess communication system of the second aspect, the message data stored in the external storage device is transmitted to the empty queue buffer during the reception waiting time of the message data in the receiving task.
The processing efficiency of message communication is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a process configuration of an inter-process communication system of the present invention.

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

FIG. 3 is a block diagram showing a configuration of a supervisory control device shown in FIG.

FIG. 4 is a diagram showing an example of a data configuration in a hard disk device.

FIG. 5 is a diagram showing a data flow between processes of the monitoring control device.

FIG. 6 is a flowchart showing a processing procedure of the monitoring process shown in FIG.

7 is a flowchart showing a processing procedure of a display process in FIG.

8 is a flowchart showing a processing procedure of a failure management process in FIG.

9 is a flowchart showing steps n4, n5, n6 and n7 in FIG.
5 is a flowchart showing the processing procedure of the transmission task of FIG.

FIG. 10 is a flowchart showing a procedure of a disk data transmission process in FIGS. 9 and 11.

FIG. 11 is a flowchart showing steps n11 and n in FIGS.
It is a flowchart which shows the processing procedure of the receiving task of 21.

FIG. 12 is a process configuration diagram of a conventional interprocess communication system.

FIG. 13 is a diagram illustrating an example of communication between processes.

14 is a flowchart showing a processing procedure of process Y in FIG.

Claims (2)

[Claims] 1. A means for executing a process including a sending task for sending message data to a queue buffer, and a means for executing a process including a receiving task for receiving message data from the queue buffer, the method comprising: , In an inter-process communication system that performs message communication between processes, when the queue buffer is full, there is a free space in the queue buffer and the message data external storage unit that temporarily stores the message data by the sending task in the external storage device in the first-in first-out format. An interprocess communication system, characterized in that, at a certain time, a message is sent from the external storage device in a first-in first-out format and is sent to a queue buffer. 2. The receiving task is provided with means for taking out message data stored in the external storage device in a first-in first-out format and transmitting the message data to the queue buffer when the queue buffer has no message data and the queue buffer has a free space. The interprocess communication system according to claim 1.