JPH04225433A - Semaphore synchronization system with canceling function - Google Patents

Abstract

PURPOSE:To quickly restart a semaphore synchronization system with a canceling function in a simple constitution and processing by providing an extension semaphore containing a canceling function and performing the synchronization and the cancel processing through plural processes with operation of the extension semaphore. CONSTITUTION:An extension semaphore 4 is provided to show three states, that is, a synchronization waiting state, a synchronization end state, and a cancel instruction state. Then the value is set in response to the number of processes. A process where a cancel event occurred writes the value of the cancel instruction state and also instructs a process waiting for the end of synchronization. At the same time, the process performs the cancel processing of its own. Meanwhile a process where no cancel event occurred reads out the value to make the process waiting for the end of synchronization complete the synchronization in a synchronization end state. At the same time, the process completes the synchronization of its own or subtracts or adds the value to wait for the end of synchronization in a synchronization incomplete state.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semaphore synchronization system with a cancellation function that uses semaphores to perform synchronization and cancellation processing.

0002

2. Description of the Related Art Conventionally, as shown in FIG. 4(a), a synchronization mechanism in parallel processing uses a semaphore 21 to synchronize a plurality of processes 1, 2, and 3 as shown in the flowchart of FIG. 4(b). Processing is performed in synchronization according to the procedure. At this time, in order to control the cancellation of the entire process when an abnormal situation occurs (for example, when an overflow occurs in calculations), a cancel flag 22 is provided as another mechanism, and one of the When an abnormality that causes cancellation occurs in a process, the cancel flag 22 is turned on, and when synchronization is established, all processes 1, 2, and 3 check this cancel flag 22,
When it was on, the cancellation process was performed respectively. This will be briefly explained below.

FIG. 4(b) shows the procedure of the synchronization mechanism in parallel processing using the semaphore 21. Process 1, 2
, 3 reads the contents of the semaphore 21 (S21), and when it is found that the value is "0" and synchronization is established (YES in S22)
) to wake up a process waiting for a semaphore (S23, start a process that has already finished processing and is in a synchronization wait state),
The synchronization ends (S24). On the other hand, when it is determined that the value is not "0" and that synchronization is not established (NO in S22), the content of the semaphore 21 is decremented by 1 and the value is written (S25).
The process enters a state of waiting for the completion of synchronization of other processes (S26).

FIG. 5 shows the procedure of a synchronization mechanism and a cancellation mechanism in parallel processing using a semaphore 21 and a cancellation flag 22. If an abnormal situation occurs in processes 1, 2, or 3 and a cancellation operation is required (Y in S31)
ES), set the cancel flag 22 to ON, and execute S3.
On the other hand, if the cancel operation is not required (S32
(NO), the process advances to S33. The contents of the semaphore 22 are read in S33, and when it is found that the value is "0" and synchronization is established (YES in S34), a process waiting for the semaphore is woken up (S35), and this woken up process reads the contents of the cancel flag 22. Read (S36), perform cancel processing when canceling (YES in S37) (S39)
, if it is not canceled (NO in S37), the synchronization process ends (S38). On the other hand, when it is determined that the value is not "0" and that synchronization is not established (NO in S34), the semaphore 21
The content is written by -1 (S40), and the process waits for synchronization completion (S41).

[0005]

[Problem to be solved by the invention] (a) of FIG. 4 mentioned above
As shown in FIG. 5, conventionally, when canceling during synchronous processing, a semaphore 21 and a cancel flag 22 were used to cancel multiple processes synchronously. Furthermore, there is a problem in that an extra cancellation flag 22 is required for cancellation, and cancellation processing cannot be started until synchronization is achieved.

An object of the present invention is to provide an extended semaphore with a cancel function, operate the extended semaphore to synchronize and cancel a plurality of processes, and quickly restart the process with a simple configuration and process.

[0007]

[Means for Solving the Problems] FIG. 1 shows a diagram illustrating the basic configuration and operation of the present invention. In (a) of FIG. 1, processes 1, 2, and 3 are processes that perform parallel processing synchronously. The extended semaphore 4 holds values representing three states: a synchronization wait state, a synchronization completion state, and a cancel instruction state.

[0008]

[Operation] As shown in FIG. 1, in the present invention, multiple processes set a value corresponding to the number of processes in the extended semaphore 4 at the start of synchronization processing, and the process in which the cancellation event occurs writes the value of the cancellation instruction state to , starts the process waiting for synchronization completion to perform the cancellation process, and cancels the own process, while the process that completes the process without a cancellation event writes the extended semaphore 4. Read the value from , and when the synchronization is complete, start another process waiting for synchronization to complete the synchronization, and also read the value of extended semaphore 4 when the own process completes the synchronization, or when the synchronization is not complete. is subtracted (or added) and waits for synchronization to complete.

[0009] Therefore, by providing an extended semaphore 4 with a cancel function and operating it to synchronize and cancel multiple processes, it becomes possible to restart quickly with a simple configuration and process. .

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the structure and operation of an embodiment of the present invention will be explained in detail with reference to FIGS. 1 to 3. Figure 1 (a
), processes 1, 2, and 3 are a plurality of processes that synchronously perform parallel processing, such as array calculations in science and technology and resource securing processing in online transactions.

The extended semaphore 4 has a value representing a synchronization wait state (for example, an integer value of 1, 2, 3, etc.), a value representing a synchronization completion state (for example, an integer value of 0), and a value representing a cancel instruction state. (negative integer values of -1, -2, etc.). Here, for example, 2 represents a state in which two processes have not completed processing. 0 represents a state in which multiple processes have completed synchronization. -2
Among them, - represents a cancellation instruction, and 2 represents that there is one process that completed processing after the cancellation instruction was issued.

Next, the operation of the configuration shown in FIG. 1(a) will be explained in detail using the flowchart shown in FIG. 1(b). (1) Among processes 1, 2, and 3 that have started parallel processing, the process that has finished reading the value of extended semaphore 4 (S1). (2) If the cancel operation occurs within the own process (YES in S2), -1 is written to the extended semaphore 4 (S3), and the process waiting for the semaphore (waiting for synchronization completion) is woken up (activated, S4).

(3) If the value of extended semaphore 4 is negative (YES in S5), it is in the cancel instruction state, so
A cancellation process is performed (S6). On the other hand, extended semaphore 4
If the value of is not 0 (NO in S5), the synchronization ends (S7) since the cancellation instruction state has not been reached. (4) In addition, if the cancel operation does not occur within the own process (NO in S2), or if the value read from extended semaphore 4 is 0 (YES in S8), all processes in parallel processing are synchronized. Since it was established, S4 to S7
starts another process waiting for synchronization completion, performs cancellation processing when the value of extended semaphore 4 is negative, and completes synchronization when it is not negative. On the other hand, if the value read from the extended semaphore 4 is not 0 (NO in S8), it is decremented by 1, the value is written to the extended semaphore 4 (S9), and the process waits for synchronization completion.

As described above, when multiple processes 1, 2, and 3 that perform parallel processing complete processing, an abnormality occurs in the own process (for example, an overflow occurs during calculation) and cancellation processing needs to be performed. , -1 (cancellation instruction state) is written to the extended semaphore 4, and other processes waiting for synchronization completion are activated to perform cancellation processing. Also, if no abnormality occurs, the value of extended semaphore 4 is 0.
When the value of extended semaphore 4 is not 0 (synchronization complete state), another process is started and cancel processing or synchronization ends according to the value of extended semaphore 4. On the other hand, when the value of extended semaphore 4 is not 0 (synchronization complete state) when the situation was not
Writes the -1 value to extended semaphore 4 and waits for synchronization completion. These processes make it possible to perform synchronization processing and cancellation processing with a simple configuration and processing, and to quickly restart the system.

FIG. 2 shows an example of synchronization and cancellation during calculation according to the present invention. This is because when large array calculations are performed in parallel by multiple CPUs (processes), such as in scientific and technical calculations, synchronization is required when passing intermediate results. If an abnormality such as an overflow occurs in the calculation results of any one CPU (process) during this synchronization, there is no point in continuing the calculation and it must be stopped immediately.
At this time, at the position of ■ or ■' synchronous processing with cancellation,
The cancellation process shown in the flowchart of FIG. 1(b) is performed. To explain specifically, (1) Processes 1, 2, 3, and 4 are Process 1 and Process 2,
Alternatively, as in process 3, the array is calculated in parallel.

(2) If an abnormality such as an overflow occurs during processing 1, processing 2, or processing 3 of any process, and it is necessary to cancel the entire parallel calculation of the array, In the synchronous processing with cancellation of or ■', the process in which the error occurred writes -1 to the extended semaphore 4 according to the flowchart in FIG. Performs cancellation processing of the own process. Then, other processes that are not waiting for synchronization completion perform cancel processing because when they read the value of extended semaphore 4 when their own processing is completed, the value is negative.

FIG. 3 shows an example of synchronization and cancellation during online transactions according to the present invention. This is to avoid deadlocks that may occur if even one resource cannot be secured when multiple resources are secured in parallel during online transaction processing. Synchronous processing with cancellation is required for this purpose. As this synchronization process with cancellation, the cancel process shown in the flowchart of FIG. 1(b) is performed at the positions of ■ and ■'. To explain specifically, (1
) Processes 1, 2, 3, and 4 secure resources in parallel.

(2) If one of the processes is unable to secure resources and it becomes necessary to cancel the entire resource securing process to avoid deadlock, synchronization with cancellation of ■ or ■' In the process, (
According to the flowchart of b), the process that cannot secure the resource writes -1 to the extended semaphore 4, activates other processes waiting for completion to perform cancellation processing, and also cancels its own process. Then, other processes that are not waiting for the synchronization to complete read the value of extended semaphore 4 when their own resource reservation is completed, and since the value is negative, they perform cancellation processing.

[0019]

[Effects of the Invention] As explained above, according to the present invention,
The extended semaphore 4 has three states: a synchronization wait state, a synchronization completion state, and a cancel instruction state, and multiple processes operate on this to perform synchronization and cancellation processing, resulting in a simple configuration. By using this process, you can synchronize multiple processes that are performing parallel processing, or perform cancel processing to quickly restart the process.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle configuration and operation of the present invention.

FIG. 2 is an example of synchronization and cancellation during calculation according to the present invention.

FIG. 3 is an example of synchronization and cancellation during online transactions according to the present invention.

FIG. 4 is an explanatory diagram of the prior art.

FIG. 5 is an example of conventional synchronization and cancellation.

[Explanation of symbols]

1, 2, 3: Process (CPU) 4: Extended semaphore

Claims (3)

[Claims] Claim 1: In a semaphore synchronization method with a cancellation function that performs synchronization and cancellation processing using a semaphore,
An extended semaphore (4) representing three states: a synchronization wait state, a synchronization completion state, and a cancel instruction state is provided, and when parallel processing by multiple processes is started, a value corresponding to the number of processes is assigned to the extended semaphore (4). Set it up,
The process in which the cancellation event occurred writes the value of the cancellation instruction state to this extended semaphore (4), and if there is a process waiting for synchronization completion, it starts it and causes it to perform the cancellation process, and also cancels its own process. , On the other hand, if a process that has completed processing without a cancellation event has read the value from the extended semaphore (4) and is in a synchronization completion state, and there is a process waiting for synchronization completion, start this process. A cancel function characterized in that it is configured to terminate synchronization, and when the self-process synchronizes or is not in a synchronization complete state, subtracts (or adds) the value of the extended semaphore (4) and waits for synchronization completion. Semaphore synchronization method. Claim 2: Performing parallel calculation as the parallel processing,
2. The semaphore synchronization system with a canceling function according to claim 1, characterized in that the entire parallel calculation is canceled when an abnormality occurs during calculation in any of the processes. 3. The above-mentioned parallel processing is characterized in that the resource securing process necessary for the online transaction is performed, and when any process fails in the resource securing process, the entire resource securing process is canceled. A semaphore synchronization system with a cancellation function according to claim 1.