JP2569918B2 - Deadlock generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electronic computer system, in which when an online program is developed, a deadlock that is effective in performing an operation check test when an online program deadlock occurs is performed. It concerns the device.

[Conventional technology]

In a concurrent process environment, in a resource sharing situation, two processes may fall into a deadlock state waiting for each other to release their resources. An example of a deadlock will be described with reference to FIG.
Now, consider a case where two tasks 1 and 2 are requesting a lock on one resource (data) as an example.

Here, there are two types of locks, a search lock and an update lock, and there are the following rules.

(1) When the search lock and the update lock are not held by another task, the invoking task can hold the search lock and the update lock.

(2) When the search lock is locked by another task, the own task can lock the search, but the update lock waits until the other task releases the search lock.

(3) When an update lock is held by another task, the invoking task waits for both the search lock and the update lock until the other task releases the update lock.

(4) When releasing the lock, both the search lock and the update lock must be released at the same time.

If there are the above rules, →→
If you try to lock in the order of →, the update lock waits and the deadlock occurs.

Conventionally, when a deadlock is generated in a program, the program locks the lock, waits for a timer or waits for an input from an operator, and performs exclusive control on a file or a database with another program (the processing described above). ) Is performed, the timer wait or the input wait of the operator is released, the lock is released, and the deadlock is generated.

[Problems to be solved by the invention]

In the conventional method described above, there was no guarantee that a deadlock would definitely occur in theory. One of the reasons is that it is uncertain when the timer wait will occur depending on the operation state of the program, and in the past, humans started the above-mentioned other programs after watching the time. Second, deadlock does not occur if the lock is applied before the above lock is completed because the occurrence of the timer wait is uncertain.

Therefore, it was necessary to verify whether a deadlock actually occurred.

Further, in the conventional method, a large amount of time is required between a timer wait and an input by an operator, and further, there is a risk of an operation error because human intervention is required.

[Means for solving the problem]

The present invention provides a deadlock generating apparatus in an electronic computer system, wherein the program of the electronic computer can generate a deadlock via the deadlock generating apparatus. A lower task start instructing means for issuing a start instruction to the lower task when the upper task is started by an operating system of the computer, and a notification from a program of the computer system. When a stop is requested, an end instruction is issued to the two lower tasks, and the operation is stopped upon receiving an end report from the two lower tasks. When an operation is requested, an operation instruction is issued to the two lower tasks. A task control unit, wherein the two lower tasks are the lower task activation instructing means; Database opening means for mutually opening the database provided via the upper task by the operating system of the computer in response to the activation instruction by the computer, and mutually exclusive control of the database in response to the operation instruction. Do
A deadlock in which one of the lower tasks generates a state in which a deadlock occurs, and the other one of the lower tasks detects that the state in which the deadlock occurs occurs, and notifies the program of the detection information. It is characterized by having a preparation means and a termination processing means for mutually closing the databases opened in response to the termination instruction and mutually issuing the termination report.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the deadlock device of the present invention. In FIG. 1, 1 is a deadlock generator according to the present invention, 2 is an upper task, 3a, 3b
Is a lower task. It is assumed that the two lower tasks actually perform the same processing at the same time.

When the upper task 2 of the apparatus 1 is started by an OS (operating system), the upper task 2 starts to operate, and starts the lower tasks 3a and 3b via the lower task start instructing means 2-1. When each of the lower tasks starts operation, first, the file specified by the OS is opened by the database open means 3-1. Here, the files used in both lower tasks are the same.

When the lower-level task has completed opening the file, the lower-level task waits for an instruction from the higher-level task. The instruction waiting state is
This is a state of waiting for synchronization between tasks, which is a so-called semaphore wait state.

Reference numeral 4 denotes an operation request notification or a stop request notification of the apparatus from a program external to the apparatus.

When the upper task receives the operation / stop request notification 4 in the lower task control means 2-2, it determines whether the request is an operation request of the apparatus or a stop request. If the request is a stop request, end instructions 6a and 6b are issued to the lower task, and the end tasks of both lower tasks 3a and 3b are waited for before the upper task 2
The operation of is ended. If it is an operation request, operation instructions 5a, 5b
To the lower tasks 3a and 3b.

Upon receiving the instruction from the upper task 2 in the deadlock preparing means 3-2, the lower tasks 3a and 3b determine whether the instruction is an end instruction or an operation instruction. Then, the files are closed, a completion report is issued, and the operation is terminated. In the case of the operation instructions 5a and 5b, first, the lower tasks 3a and 3b respectively lock the data of the file with the search. The search lock refers to an exclusive control in which search processing of certain data from another task is permitted, but update processing is not permitted. Here, the data for which both lower tasks lock the search are the same data.

Next, the lower tasks 3a and 3b synchronize with each other. This synchronization is to prevent both tasks from proceeding to further processing until both tasks have completed the above-described search lock operation.

Next, each lower-level task further places an update lock on data previously locked with a search. The update lock is an exclusive control that does not allow search processing and update processing from other tasks. In the case of the present embodiment, since the two lower tasks 3a and 3b operate asynchronously after the above-described synchronous processing, it is not known which performs the update lock processing first. Assume that update lock processing has been performed. Since the search lock has already been applied to the data by the lower task 3b, the lower task 3a enters a wait state in the update lock processing. continue,
The lower task 3b attempts to perform the update lock processing, but the data is also locked by the lower task 3a. Here, when the lower task 3b enters the waiting state, the lower task 3a and the lower task 3b enter a waiting state forever, that is, a so-called deadlock state. Therefore, in the OS, the lower task 3b notifies the update lock failure without waiting.

The lower task 3b notified of the update lock failure from the OS
An update lock failure notification 7b is sent to the program that has operated this device.

Here, it is assumed that the program that has operated the apparatus has also locked the search for the same data in the same file. After the program receives the update lock failure notification 7b from the lower task 3b and attempts to lock the data, the OS is notified of the update lock failure as in the lower task 3b. Thus, the update lock failure, that is, a deadlock occurs in the program that has operated the present apparatus.

Thereafter, since the program that has operated the apparatus releases the search lock and the lower task 3b also releases the search lock, the lower task 3a normally completes the update lock processing and releases both the search and update locks. .

In this way, both lower tasks again wait for an instruction from the upper task.

Here, the case where the lower task 3a has performed the update lock processing first has been described. On the contrary, the same applies to the case where the lower task 3b has performed the update lock processing first.
3a performs update lock failure notification 7a.

FIG. 2 shows an example in which the deadlock generator 1 according to the present invention is applied to an operation check test of an online transaction processing program 9 under development on an online subsystem 8 at the time of deadlock.

As shown in the figure, the online transaction processing program 9 performs a search lock process, issues an operation / stop request notification 4 indicating a deadlock occurrence request, and receives an update lock failure notification (7a / 7b) before updating lock. When the processing is performed, the online subsystem 8 detects the update lock failure and performs the processing of releasing the search lock.

As described above, by using the deadlock generation device according to the present invention, it is possible to easily generate a deadlock in the online transaction processing program under development.

〔The invention's effect〕

As described above, by using the deadlock generation device of the present invention, it is possible to generate a deadlock reliably and without any need for operator intervention, and a deadlock operation confirmation test during online program development can be performed. It can be done very efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a deadlock device according to the present invention, FIG. 2 is a diagram showing an application example of a deadlock generating device according to the present invention, and FIG. 3 is a diagram showing the principle of deadlock generation. It is. 1 ... deadlock generator, 2 ... upper task, 2-
1 ... lower task start instructing means, 2-2 ... lower task control means, 3-1 ... database open means, 3-
2 deadlock preparation means, 3-3 termination processing means, 3a, 3b lower task, 4 operation / stop request notification, 5a, 5b operation instruction, 6a, 6b end instruction, 7a, 7b…
... Update lock failure notification, 8 ... Online subsystem, 9 ... Online transaction processing program.

Claims (1)

(57) [Claims] 1. A deadlock generating device in an electronic computer system, wherein a program of the electronic computer is capable of generating a deadlock via the deadlock generating device. A lower task, wherein the higher task receives a notification from a program of the computer system, and receives a notification from a program of the computer system, wherein the lower task receives a notification from a program of the computer system when the upper task is started by an operating system of the computer. Issues a termination instruction to the two lower tasks when requesting a stop, and stops upon receiving a termination report from the two lower tasks, and issues an operation instruction to the two lower tasks when requesting operation A lower task control unit, wherein the two lower tasks are the lower task activation instruction; Database opening means for mutually opening a database provided by the operating system of the computer via the upper task in response to the start instruction by a stage, and mutually exclusive control of the database in response to the operation instruction Do
A deadlock in which one of the lower tasks generates a state in which a deadlock occurs, and the other one of the lower tasks detects that the state in which the deadlock occurs occurs, and notifies the program of the detection information. A deadlock generating apparatus, comprising: a preparation unit; and a termination processing unit that closes the database that has been opened in response to the termination instruction and mutually issues the termination report.