JP3527389B2 - Inter-process communication method and inter-process communication system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to inter-process communication in a computer system, and more particularly to an inter-process communication method and inter-process communication system in which transmissions of a transmission process are received by a plurality of reception processes.

[0002]

2. Description of the Related Art In a computer system, a message from the outside is often taken in and a process according to the message is executed by an internal process. in this case,
It is necessary for multiple processes to receive the same message. For example, in an FA system or the like, data is shared and exchanged between a plurality of processes. High speed and real time are required for the exchange. In addition, when sending and receiving messages between processes, it is important to eliminate omissions in sending and receiving.

As a method of synchronization control for realizing such inter-process communication, for example, Japanese Laid-Open Patent Publication No. 5-100874 (cited example 1) prepares a task for transmission / reception processing so that one pair can be used in the transmission / reception process. The method of performing the synchronous control of No. 1 is disclosed. The sending task sets the event, the semaphore, and the like to notify the sending, and sends the message, and the receiving task resets the event, the semaphore, etc. after receiving the message.

Further, in Japanese Unexamined Patent Publication No. 4-256029 (cited example 2), when a message is transmitted from a task on the transmitting side to a plurality of receiving tasks, an exclusion target area for displaying the execution occupied state of each task is provided, It has been proposed to send from a sending task to multiple receiving tasks via a single queue terminal.

[0005]

In the conventional interprocess communication, when considering a plurality of reception waits in one transmission process, if the one-to-one transmission method of the above-mentioned reference 1 is used, the transmission process will be performed for each reception process. It is necessary to repeat the process of sending a message to. For this reason, many resources such as events and semaphores used as notification means between processes are required, and the process load increases, resulting in a decrease in process processing speed. In addition, the number of man-hours for creating a program increases because the program becomes complicated and redundant.

Here, in the case of considering sending a message to a plurality of processes at once, it is not possible to let the receiving process side reset events such as an event notifying the sending and a semaphore. If it is left to the receiving process side, after the resetting process receives it, other receiving processes cannot receive it, resulting in leakage of transmission and reception. on the other hand,
In order for the process on the sending side to reset an event, a semaphore, etc., it is necessary to know that all processes waiting for reception have finished receiving. However, this method cannot be realized because the receiving process side cannot know that it is the last message acquirer.

As described above, when a plurality of receiving processes receive a message by one transmission, it is difficult to establish a timing for resetting an event, a semaphore, etc. for synchronous control of the transmitting processes. Even if it can be realized, if the receiving process waits for reception immediately after the transmitting process resets an event, a semaphore, etc., there is a timing at which reception is missed.

By the way, in the 1-to-n transmission method of the above-mentioned reference example 2, if the number of receptions is known in advance on the transmission side, the transmission processing can be ended by the reception response message from the reception side. However, in the inter-process communication in which the number of receiving sides varies, if there are more receiving processes than the set number of receptions, reception omission occurs, and if there are less receiving processes than the set number of receptions, the transmission process cannot be terminated. That is, with the transmission method of the second reference example, it becomes impossible to perform synchronous control for a fluctuating reception process.

In view of the problems of the prior art, it is an object of the present invention to provide an interprocess communication method and a communication system therefor capable of transmitting without fail to a plurality of reception waiting processes with one transmission notification.

[0010]

The above-mentioned object is to perform a transmission process in which a transmission process fetches a message from the outside and writes it in a shared memory, and a reception process in which a plurality of reception processes reads the message from the memory and processes it. In the inter-process communication method in a computer system for performing the above, the transmission process exclusively controls access to the memory to write the message, terminates the transmission process when there is no reception process waiting for reception, and receives the reception waiting. When a process exists, a transmission notification is performed after the writing, and after confirming that all the reception processes waiting for the reception have received the transmission notification, the transmission notification is reset, and the transmission processing ends. To be achieved.

From the reception side, the reception process exclusively controls access to the memory to refer to the memory, and when the message can be read, the process according to the message is executed to perform the reception process. Finished,
On the other hand, when the message cannot be read, the sending process is notified that it is waiting to be received, the exclusive control for the memory is released thereafter, and when the sending notification is received from the sending process, the reception is sent by the sending. This is accomplished by making a second reference to the memory after informing the process.

More specifically, 1 waiting for reception
Or a plurality of receiving processes indicate its existence by a read lock on the first file, unlock the first file when receiving a transmission notification from the transmitting process, and the transmitting process writes the message. After that, the file is write-locked, and when the existence of the waiting for reception is known from the failure of the lock, an event is set and the transmission is notified, and all of the waiting for reception from the succeeding write lock of the file The reception process confirms that the transmission notification has been received, and then resets the event and ends the transmission process.

The transmission process write-locks a second file that exclusively controls access to the memory from the start to the end of the transmission process, and the reception process from the start to the end of the reception process or the first process. The second file is write-locked until the file is read-locked.

The interprocess communication system to which the method of the present invention is applied includes a message storage unit for storing messages to be transmitted and received between processes, a transmission process for writing a message fetched from the outside into the message storage unit, and the message storage unit. A plurality of (n) receiving processes that read a message from a message and perform processing according to the message, and for one-to-n inter-process communication in a computer system, in which the transmitting process is waiting for receiving Sending notification means for notifying that a message has been written to the message storage unit and resetting the notification when all the receiving processes waiting to receive the notification receive the receiving process with respect to the sending process. That it is waiting to be received, and when the notification is received, the reception News, and after all of the reception process of the reception waiting is made known, characterized in that a notification processing exclusive control means for enabling resetting of the transmission indication means by the transmission process.

Further, the notification process exclusive control means is constituted by an exclusive control file in which each of the reception processes waiting for reception performs a read lock and the transmission process locks a write.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an interprocess communication system of the present invention.

The interprocess communication system includes a transmission processing means (hereinafter referred to as a transmission process) 10 for receiving a message from the outside and a transmission processing, a reception processing means for receiving a message from the transmission process 10 and executing the processing (hereinafter referred to as a reception processing means). (Reception process) 20, message storage unit 11 used for passing messages, and transmission process 10 from reception process 20 to end of transmission processing (writing of message)
A transmission / reception exclusive control unit 1 having a transmission notification unit (hereinafter, an event) 12 for notifying the message, and a file 13 for performing an exclusive process on the message storage unit 11 between the transmission / reception processes.
4, notification processing exclusive control means 16 having a file 15 for performing exclusive processing of notification processing between the transmission process 10 and the reception process 20, and a process input / output interface (PI / O) 17 for taking in a message from the outside is doing. Access to the transmission notification means 12 from the transmission process 10 and the reception process 20 is realized by a function of an OS such as a semaphore.

The exclusive processing using the file 13 or the file 15 is realized by each of the transmission / reception processes locking the file. The file lock (hereinafter, simply referred to as a lock) is a function that prevents other processes from accessing the corresponding file. Therefore, each process locks the corresponding file before the process for which exclusive control is desired, performs the process after the locking is successful, and releases the lock for the corresponding file after the process ends. By using this method for each process, exclusive control of processing between processes becomes possible.

There are two types of locks for the file 13 or the file 15: a write lock and a read lock. When a write lock is applied, other processes cannot perform both write lock and read lock on the file. When a read lock is applied, another process can execute only the read lock on the file.

A write lock is used when processing is exclusively controlled between the transmitting and receiving processes, and a write lock is used by the sending process 10 when receiving exclusive control between the sending process 10 and a plurality of receiving processes 20. 20
Performs a read lock. Further, as a method of requesting a file lock, there are a method of suspending the process until the file can be locked and a method of returning the process to the process as a lock failure when the file cannot be locked.

Next, the event 12 will be described. The event 12 has two states, a set state and a reset state. Typical processes that can be executed by the transmission / reception process on the event 12 include setting the event 12 to the set state, setting the event 12 to the reset state, and suspending the process until the event 12 is set. There are three.

In this embodiment, the event 12 is used to send a notification from the sending process 10 to the receiving process 20, that is, to notify the completion of writing the message in the message storage unit 11. The sending process 10 is the receiving process 20
When the transmission notification is sent to the event 12, the event 12 is set. When the reception process 20 waits for reception from the transmission process 10, it waits for the event 12 to enter the set state. Further, when the transmission process 10 ends the transmission process, the event 12 is reset. Event 1
The initial state of 2 is a reset state.

FIG. 2 is a flow chart showing the procedure of processing of the transmission process. The transmission process 10 fetches a message from outside via the PI / O 17 (s20
1). Next, the file 13 is write-locked (s2
02). This prohibits writing and reading from the message storage unit 11 by other processes. If the write lock cannot be made, one of the receiving processes 20 is reading and waits until the write lock is made.

After the write lock is successful, the message to be transmitted is written in the message storage unit 11 (s20
3). Next, the file 15 is write-locked, and it is determined whether the lock is possible (s204). If the write lock is successful, there is no receiving process 20 waiting for reception.
Of course, since the file 13 is write-locked, there is no new waiting for reception. So file 1
Release the lock of 5 (s210), and further file 13
The lock is released (s211), and the transmission process ends.

On the other hand, if the write lock fails in step s204, the process proceeds without interruption, the event 12 is set, and the receiving process 20 is notified of the transmission (s205). Next, the file 15 is write-locked again (s206). If the lock is unsuccessful, the process is interrupted and the process waits until the lock can be made (WAIT).
The success of the write lock in this step means that all the reception waiting processes have received the transmission notification and released the read lock of the file 15.

After the write lock of the file 15 is successful, the event 12 is reset (s207).
That is, the processing of the transmission notification ends. Next, the lock of the file 15 is released (s208), and the file 1 is further released.
The lock of No. 3 is released (s209), and the transmission process ends.

As described above, only when the lock is executed in step s204, the WAIT is not performed even when the lock is impossible,
Return processing to the process. However, when the lock is executed in other steps, the process of the receiving process 20 is included, and the process of the process is suspended until all the processes can be locked.

FIG. 3 is a flowchart showing the processing procedure of one receiving process. The receiving process 20 first writes and locks the file 13 (s301).
If you cannot lock it, wait until you can lock it.

After the write lock is successful, the message is read from the message storage unit 11 and it is determined whether the message can be read (s302). If the message has already been written in the message storage unit 11 and the reading of the message has succeeded, the lock of the file 13 is released (s307), and the process according to the received message is executed (s308).

If the message cannot be received in step s302, the file 15 is read and locked (s30).
3). As a result, the transmission process 10 is notified of the existence of the reception waiting process, and the reset of the event 12 is prohibited. After the read lock is successful, the lock of the file 13 is released (s304). As a result, the lock of the file 13 of the transmission process 10 succeeds, and the message can be written in the message storage unit 11.

Next, WAIT is performed until the event 12 becomes the set state, and the transmission notification from the transmission process 10 is waited (s305). When the event 12 enters the set state and the transmission notification from the transmission process is received, the lock of the file 15 is released (s306). And step s3
Returning to 01, the file 13 is write-locked and the message is read in step s302. Here, since the transmission notification is received, the reading does not fail.

The above is the transmission process 10 and the reception process 2.
The process flow is 0. The transmission / reception process 10 uses the exclusive control file 13 and the file 15 and the event 12 to perform synchronous control of message transmission / reception.

In particular, the reception process 20 waiting for reception uses the lock of the file 15 to perform exclusive control over the processing of other processes so that the transmission notification from the transmission process 10 is not missed. That is, the receiving process 20 that has failed to read the message is processed in step s30.
Before waiting for reception in step 5, the file 15 is read and locked in step s303, thereby informing the transmission process 10 that it is waiting for reception. Since it is a read lock, the other receiving process 20 can also lock the file 15 and similarly notify the transmitting process 10 to wait for reception.

The transmission process 10 writes and locks the file 15 in step s204, and this process is to confirm whether or not there is a reception waiting process waiting for a transmission notification from the transmission process 10. The sending process 10 that has completed the writing in the message storage unit 11 and knows the existence of the reception waiting process
2 is set and a transmission notification is sent to the reception waiting process. At this time, in order to confirm that all the receiving processes waiting for notification have received the notification, the file 15
Write-lock. When this write lock succeeds, in other words, when all the reception waiting processes receive the transmission notification and release the read lock of the file 15, the transmission process 10 resets the event 12 and ends the transmission notification. Thereby, the synchronous control of the transmission notification process can be realized.

If the transmission process 10 succeeds in the write lock of the file 15 in step s204, there is no reception waiting process waiting for notification. Therefore, the transmission process 10 releases the lock of the file 15 and the file 13 that are executing the exclusive control without sending the transmission notification by the event 12, and ends the transmission process.

By the way, at step s302, the receiving process 20 fails to read the message, and at step s302.
If the transmission process 10 executes a transmission process while the file 15 is read and locked in 303 (s203, s2
04-s210, s211), there is a timing when the receiving process 20 cannot receive the transmission notification of the transmitting process 10. Therefore, the following exclusive control using the file 13 is performed so that the transmission process is not executed at the above timing.

The file 13 is locked at the beginning of the processing in both the transmission and reception processes 10 and 20, and the transmission process 10 ends the transmission (s202 to s209 / s202 to
s211), the reception process 20 ends reception (s30)
7) or before waiting for transmission notification (s301 to s30
4) Continues. By this process, exclusive control of reading and writing in the message storage unit 11 is performed, and the above-mentioned timing of reception omission is prevented.

In step s303, the reception process 20 executes the read lock of the file 15 and then releases the lock of the file 13. Therefore, the receiving process 2
While 0 is executing the communication waiting process, the sending process 10
Cannot perform send processing. On the other hand, when the transmission process 20 starts the execution of the transmission process and locks the write of the file 13 in step s202, the reception process 20 cannot execute the reception process except the process that is performing the notification waiting process. When the receiving process 20 is executing the notification waiting process, the transmitting process 20 always executes the notification process as described above, and therefore the reception omission does not occur.

In addition, the receiving process 20 executes step s30.
The reason why the file 13 is released in 4 is to avoid the deadlock. This allows the other receiving process 20
Enables the receiving process and the sending process 10 to perform the sending process.

FIG. 4 is a time chart explaining the operation of the interprocess communication system of this embodiment. The processing step numbers of the transmission process and the reception process (corresponding to FIGS. 2 and 3) and the process numbers that lock the lock file 13 and the lock file 15 at the respective processing points are shown in time series.

FIG. 4A shows an example in which the operation is started from the transmission process. In this case, since the transmission / reception lock file 13 is write-locked in step s202,
The receiving process cannot enter the receiving process until the sending process completely finishes sending (writing) the message. Therefore, when the receiving process enters the receiving process in s301, the message has already been written, and the message storage unit 11 is referred to complete the message reception. Therefore, the transmission notification process is also not performed.

FIG. 6B shows an example in which the operation starts from the receiving process and the transmitting process interrupts in the middle.
While the reception process is operating, the transmission process cannot enter the transmission process until the file 13 is released (s304) and the transmission notification waits. However, when the transmission process operates, the reception process cannot perform operations other than the transmission notification reception process (s306; event reception) and the release of the file 15.

In FIG. 7C, the operation starts from the receiving process, and when the file 13 is released in step s304, the receiving process starts operating. Even in this case, the situation is the same, and the transmission process cannot enter the transmission process until all the reception processes wait for the transmission notification. Also,
Until all waiting processes receive the event,
Does not terminate the transmission process (event reset).

As described above, in the interprocess communication system of this embodiment, the receiving process 20 is the message storage unit 1.
When referring to 1 (reception processing), the transmission process 10 does not perform message writing processing (transmission processing), and does not perform transmission notification processing. Also, while the reception waiting process is executing the transmission notification waiting process, since the transmission notification (event set) of the transmission process is not performed, there is no omission of the reception notification of the reception waiting process, and the reception waiting process can receive reliably. .

[0045]

According to the present invention, a receiving process waiting for reception shows it as a read lock and issues a transmission notice, and a transmitting process uses a write lock to confirm that all processes waiting for reception have received the transmission notice. Since the confirmation is completed and the transmission notification is terminated, a plurality of receiving processes can receive the transmission process once without fail, and the load of the transmitting process can be reduced and the processing speed can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an interprocess communication system showing an embodiment of the present invention.

FIG. 2 is a flowchart showing a transmission process of a transmission process.

FIG. 3 is a flowchart showing a receiving process of a receiving process.

FIG. 4 is a time chart illustrating a time series operation of transmission / reception processing.

[Explanation of symbols]

10 ... Transmission processing means (transmission process), 11 ... Message storage unit, 12 ... Transmission notification means (event), 13 ... Send / receive exclusive control file, 14 ... Interprocess exclusive control means, 15 ... Reception confirmation exclusive control file, 16 ... Transmission notification processing synchronization means, 17 ... Process input / output interface, 20 ... Reception processing means (reception process).

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-63-108452 (JP, A) JP-A-9-6735 (JP, A) JP-A-9-101901 (JP, A) JP-A-7- 200494 (JP, A) JP-A-5-100874 (JP, A) JP-A-4-256029 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G06F 9/46 G06F 15 / 163-15/177

Claims (6)

(57) [Claims] 1. An interprocess communication method in a computer system, wherein a sending process receives a message from the outside and writes it in a shared memory, and a receiving process in which a plurality of receiving processes read the message from the memory and process it. , The sending process exclusively controls access to the memory to write the message, ends the sending process if there is no receiving process waiting to receive, and writes the message if there is a receiving process waiting to receive After that, a transmission notification is performed, and after confirming that all the reception processes waiting for the reception have received the transmission notification, the transmission notification is reset and the transmission processing is ended. 2. An interprocess communication method in a computer system, wherein a transmission process receives a message from the outside and writes it in a shared memory, and a plurality of reception processes performs a reception process in which the message is read from the memory and processed. , The receiving process exclusively controls access to the memory, refers to the memory, and when the message can be read, executes a process according to the message and ends the receiving process, while the message cannot be read. If not, it informs the sending process that it is waiting to receive, then releases the exclusive control to the memory,
An inter-process communication method, comprising: receiving a transmission notification from the transmission process, notifying the transmission process of the reception, and then referring again to the memory. 3. An inter-process communication in a computer system that performs a transmission process in which a transmission process fetches a message from the outside and writes it in a shared memory, and a reception process in which a plurality of reception processes reads the message from the memory and processes it. In the method, one or more receiving processes waiting to receive indicate its presence by a read lock on a first file, unlock the file when a send notification is received from the sending process, After the process writes the message,
When the file is write-locked and the existence of the reception wait is known from the failure of the lock, an event is set and the transmission notification is sent, and all reception processes waiting for reception from the succeeding write lock of the file are received. An interprocess communication method comprising: confirming that the transmission notification has been received, and then resetting the event and ending the transmission processing. 4. The transmission process according to claim 3, wherein the transmission process write-locks a second file that exclusively controls access to the memory from the start to the end of the transmission process, and the reception process ends from the start to the end of the reception process. Until the first file is read-locked or the second file is write-locked. 5. A message storage unit used for passing a message between processes in a computer system, a transmission process for writing an externally fetched message to the message storage unit, and reading the message from the message storage unit according to the message. In an inter-process communication system having a plurality of (n) receiving processes that perform different processing and performing message communication between one-to-n processes, the transmitting process with respect to receiving processes waiting for reception,
Transmission notification means for notifying that a message has been written in the message storage unit, and resetting the notification when all the receiving processes waiting to receive the notification, and for the transmitting process, the receiving process Notification processing for informing that the reception is to be waited and for notifying the reception when the notification is received, and for enabling the transmission notification means to be reset by the transmission process after all the reception processes waiting for the reception have notified An interprocess communication system characterized in that exclusive control means is provided so that one or a plurality of receiving processes waiting for reception can receive without a single notification from the transmitting process. 6. The exclusive control file according to claim 5, wherein the notification process exclusive control means is composed of an exclusive control file in which each of the reception processes waiting for reception performs a read lock and the transmission process performs a write lock. Interprocess communication system.