JPH03174633A - Multi-task control system - Google Patents

Abstract

PURPOSE:To eliminate the need for the monitoring job of an operator by providing a deadlock detecting function on the task control function of an operating system. CONSTITUTION:A task group control block TGCB 121 includes a task counter 1211 which shows the number of tasks that are started and not finished yet and a deadlock detection counter 1212 which shows the number of tasks of a practicable state or an executing state. Whether the state of the counter 1212 is '0' or not is decided, and when it is '0' it means that all tasks that are not finished yet are kept waiting and a deadlock state is detected for these unfinished tasks. In this case, the tasks kept waiting are never practicable again and therefore finished forcibly by an operating system. Thus the monitoring jobs of an operator can be omitted.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a multi-task control method for an information processing system. This invention relates to a multitask control method that can detect deadlocks between multiple tasks.

[Conventional technology]

In multitask processing in information processing, exclusive control and synchronization control are frequently performed between multiple tasks that constitute one job. however.

If there is a programmatic error in exclusive control or synchronization control,
The entire multitasking program is stalled (
(deadlock situation) may occur.

In conventional systems, there was no means to detect deadlocks caused by program errors in exclusive control or synchronization control of multitasking programs. Therefore, 7'
``The operator determined whether or not a black lock had occurred, and the entire multitasking program in which the black lock occurred was forcibly terminated using a manual command from the operator.

[Problem to be solved by the invention]

As mentioned above, the system does not have a means to detect a deadlock situation in multitasking Grodarum, so the operator must determine whether or not there is a deadlock situation, and the operator must also take action. The problem was that it took time and effort.

[Means and effects for solving the problems] The present invention has the following features.

A multitasking job in which the state transitions of each task constituting a multitask job from the execution state to the standby state and from the standby state to the execution state depend only on events that occur due to the execution of other tasks within the job. A task job has a counter that holds the number of executable tasks in the common area of multiple tasks that make up one job, and when the task is created, when the task changes from the standby state to the executable state, and when the task is in the execution state. and means for detecting that the number of executed tasks indicated by the updated result is O.

According to the present invention, by providing the system with an executable task number counter as deadlock monitoring means, it is possible to eliminate the need for operator monitoring work.

〔Example〕

The present invention will be explained with reference to the drawings.

As used in this specification, "task standby state" means
A state in which a task depends on the execution of another task in order to become executable. (I10 wait etc. are not included) FIG. 81 is a configuration diagram for explaining one embodiment of the present invention.

In the figure, the main storage device 1 is divided into a system area 11 and a user area 12.

The system area 11 includes an execution queue 111 for managing task execution. There is a waiting queue 112 that manages waiting tasks.

The user area 12 is further divided into a task group common area that is commonly accessed from the same multitasking job group, and a task individual area that is prepared for each task.

The task group common area contains TGCB (TASKGROU), which is a collection of control information for multitask programs.
There is a semaphore 123 for synchronizing tasks. T.G.C.
B 121 includes a task counter 1211 that represents the number of tasks that have been activated but have not finished executing, and a deadlock detection counter 1212 that represents the number of tasks that are in an executable state or an execution state. TGCB 121 is
Initialized by the operating system before the start of execution of a multitasking program, in particular task counter 1
211 and the deadlock detection counter 1212 are set to "0" as initial setting values. Semapho 123
contains a status word 123 representing the state of the event.
1. A pointer 1232 to the waiting queue 112 is displayed.

In the task individual area, there is a TCB (TASK C0NTR0L BLOCK) which is a collection of control information regarding tasks.
) 122 (indicated by 1221 to 122C in the figure). Pointer 1 of TGCB 121 in TCB 122
221 (indicated by 1221a to 1221e in the figure) is set.

FIG. 2 is a flowchart of task activation processing that is performed in the configuration of this embodiment described above. #i when starting a task.

The task counter 1211 is increased by +IL (821), and the deadlock detection counter 1212 is also increased by 1 (822).

FIG. 3 is a flowchart of the task execution termination process.

During task execution termination processing, the task counter 1211 is set to -tL (S3x), and the deadlock detection counter 1212 is set to -tL (S3x).
is also -1 (832).

Next, determine whether the task counter 1211 is r'=OJ and the deadlock detection counter 1212 is "O" (833), and if this is the case, there is a task that is in a standby state and has not finished executing. This means that a deadlock situation can be detected. In this case, the task in the standby state will never become executable again, so the operating system will forcefully terminate it (8
34).

If the task counter 1211 is "0", it means the end of the entire program, and the end processing of the program is performed.

FIG. 4 is a flowchart of event waiting processing.

In the event waiting process, first, the status word 1231 of the semaphore 123 is read (841), and the state of the status word 1231 is determined (842).

If the event has not been notified, the task is placed in a waiting state (843), and the deadlock detection counter 1212
is decreased by 1 (844).

Next, it is determined whether the deadlock detection counter 1212 is "0" (545), and if it is in this state, it means that all tasks that have not finished executing are in the waiting state, and the deadlock state has not occurred. Can be detected. In this case, the task in the standby state will never become executable again, so it is forcibly terminated by the operating system (8
46).

FIG. 5 is a flowchart of event notification processing.

In the event notification process, the status word 1231 of the semaphore 123 is set to an event occurrence state (851).

It is determined whether there is a task waiting for an event (852).

If there is a task waiting for the event, it is set to executable state (853) and the deadlock detection counter 121 is set.
Add the number of tasks made executable to 2 (854)
.

FIGS. 6 and 7 are examples showing changes in the task counter 1211Th and the deadlock detection power counter 212 when a multitasking program is executed.

The embodiment shown in FIG. 6 will be described with reference to FIGS. 1 to 5.

FIG. 6 is an example where deadlock is not detected.

When task l is activated (861), task activation processing (
As shown in FIG. 2), the task counter 1211 and the put-90 detection counter 1212 are incremented by 1.

When task 2 is activated (862), task activation processing (
According to FIG. 2), the task counter 1211 and the deadlock detection counter 1212fc+1.

When task l becomes event wait (863), the deadlock detection counter 1212't--1 is incremented by the event wait process (FIG. 4). At this time, since the deadlock detection counter 1212 is F''-zOJ, no deadlock is detected.

When task 2 issues an event notification (S64), the deadlock detection counter 1212 is incremented by 1 as per the event notification process (FIG. 5). Task l becomes executable and execution is resumed.

When the execution of task 2 is completed, the task counter 1211 and the deadlock detection counter 1212 are decremented by 1 according to the task execution termination process (FIG. 3).

At this time, the deadlock detection counter 1212 indicates r)OJ
Therefore, deadlock is not detected.

When the execution of task 1 ends (866), the task counter 1211> and the deadlock detection counter 1212i-1 are set by the task execution end process (FIG. 3). At this time, since the task counter 1211 is -'', no deadlock is detected.

Next, the embodiment shown in FIG. 7 will be described with reference to FIGS. 1 to 5. FIG. 7 is an example of detecting deadlock.

When task 1 is activated (S71), task activation processing (
As shown in FIG. 2), the task counter 1211 and deadlock detection counter 1212 are incremented by 1.

When task 2 is activated (872), task activation processing (
According to FIG. 2), the task counter 1211 and the deadlock detection counter 1212 are incremented by 1.

When task 1 enters the event wait state (873), the deadlock detection counter 1212 is decremented by 1 through the event wait process (FIG. 4). At this time, since the 7'' deadlock detection counter 1212 is "NO", no deadlock is detected.

In this state, if task 2 also waits for an event (874), the event wait process (Figure 4) will cause
Since the deadlock detection counter 1212 is incremented by 1 and the deadlock detection counter 1212 becomes rOJ, a deadlock is detected. When a deadlock is detected, all tasks in the multitask group (in this case, task 1 and task 2) are forcibly terminated (875).

Task counter 1211. Deadlock detection counter 1
212. D and semaphore 123 access.

Exclusive control between multiple processors.

In this embodiment, the task counter 1211 detects the end of execution of the final task when executing a multitask program, but if the final task is known by another method, there is no need to use the task counter 1211.

〔Effect of the invention〕

As described above, the present invention provides a deadlock detection function in the task management function of the operating system, and has the advantage of being able to reliably detect deadlocks.

! Ta. This has the effect of eliminating the need for labor and time such as monitoring operators and dealing with deadlocks.

[Brief explanation of the drawing]

FIG. 1 shows an example of the configuration inside the main storage device when the present invention is implemented. FIG. 2 is a flowchart of task activation processing. FIG. 3 is a flowchart of task execution termination processing. FIG. 4 is a flowchart of event waiting processing. Figure W15 is a flowchart of event notification processing. FIG. 6 shows an example in which no deadlock is detected during execution of a multitasking program. FIG. 7 shows an example in which a deadlock is detected during execution of a multitasking program. 1... Main storage device, 11... System area, 12.
...User area, 111...Execution queue, 112...
・Waiting queue, 121...TGCB (TASK
GROUP C0NTR0LBLOCK), 1211
...Task counter, 1212...Deadlock detection counter, 122...TCB (TASKCONT
ROL BLOCK), 1221...TGCB pointer, 123...Semaphore, 1231...Status word, 1232...Waiting queue pointer.

Claims (1)

[Claims] The state transition of each task constituting a multitask job in the information processing device from the execution state to the standby state and from the standby state to the execution state is caused by an event that occurs due to the execution of other tasks within the job. In a multi-task job that only depends on the job, a counter that holds the number of executable tasks is provided in a common area of multiple tasks constituting one job, and when a task is generated and when a task changes from a standby state to an executable state, and means for updating the counter when changing from a running state to a standby state and when a task finishes executing, and an executable task indicated by the counter even though there is a task that has not finished executing after being started. 1. A multitask control system comprising: means for detecting that the number is 0, and detecting a deadlock state.