JPH0452492B2 - - Google Patents

Description

[Detailed description of the invention]

<Technical Field> The present invention relates to a processing method when a deadlock occurs in a system in which a plurality of tasks execute processing by sharing a plurality of file resources and has an automatic deadlock release method. <Prior art> Conventionally, in a data processing system in which multiple tasks share multiple file resources to execute processing,
When a deadlock state occurs between tasks due to exclusive control on a resource basis, backout processing is performed using the history information that is the data before the update that is output with the file update, the deadlock is automatically released, and the current task is immediately processed. is being re-executed. Normally, even if a deadlock occurs using the method described above, the process can be completed by re-executing. However, in the case of processing in which multiple tasks access multiple file resources in different orders as shown in FIG. 1, even if automatic deadlock release is performed and reprocessing is performed, deadlock will again occur between the multiple tasks. This happens when,
Deadlocks and reprocessing occur between multiple tasks, resulting in incomplete processing. The above problem will be specifically explained with reference to FIG. In Figure 1, tasks t ₁ and t ₂ store multiple file resources R ₁ , R ₂ ,...Rn in task t _1.
In the order of P ₁₁ , P ₁₂ , _... , P ₂₁ , P ₂₂ ,
…, when accessing in reverse order,
When task t ₁ accesses file resource Rm and holds it exclusively, when task t ₂ accesses from file resource Rn and accesses file resource Rm,
Task _t2 is placed in a waiting state due to exclusive control of each resource. Then, when task t ₁ attempts to access file resource R _n+1 , file resource R _n+1 is accessed by task t _2.
becomes an exclusively held deadlock, automatically releases the deadlock, and performs reprocessing.
Task t ₁ again accesses file resource R ₁ . Task _t2 is released from the waiting state and processing proceeds. When task t ₂ accesses file resource R _n- 〓 and holds it exclusively, task t ₁ becomes waiting when it accesses file resource R _n- 〓. after that,
When task t ₂ accesses file resource R _n- 〓 _-1 , file resource R _n- 〓 _-1 is held exclusively by task t ₁ , so it becomes deadlocked, and task t ₂ automatically releases the deadlock. Perform reprocessing. Task t ₂ will access file resource R _o again. This time, a similar deadlock occurs with the file resource R _n+ 〓. In this way, deadlock and reprocessing are repeated between multiple tasks t ₁ and t ₂ . When this happens,
Conventionally, not only the throughput of processing multiple tasks t ₁ and t ₂ was reduced, but also the processing of either task t ₁ or t ₂ had to be forcibly stopped and restarted. <Object of the Invention> Therefore, an object of the present invention is to provide a data processing system in which a plurality of tasks execute processing by sharing a plurality of file resources and which has an automatic deadlock release method, by controlling intertasks by exclusive control on a resource basis. To provide a delayed reprocessing system when a deadlock occurs, which solves the problem that when a deadlock occurs, deadlock and reprocessing are repeated and the process is not completed. <Structure of the Invention> The present invention provides a reprocessing management table that records the number of times of reprocessing and link information of tasks that generate waiting tasks for each task, and when a deadlock state occurs between tasks and automatic deadlock release processing is completed. The number of times of reprocessing in the reprocessing management table is counted up, and when this number of reprocessing reaches a predetermined value, the link information of the waiting task and the task that causes waiting is registered, the waiting task is placed in a waiting state, and waiting is generated. When the processing of the task is completed and the resources are released, the waiting task is activated by the link information and reprocessed. <Example> An example of the present invention will be described below with reference to the drawings. FIG. 2 shows a first embodiment of the present invention,
It shows the temporal flow of processing of two tasks t ₁ and t ₂ . When tasks t ₁ and t ₂ are performing a plurality of file access processes P _1o and P _2o , when a deadlock state D _l occurs in task t ₁ , automatic deadlock release processing Bo is performed in task t ₁ . When the automatic de-locking process Bo is completed,
The task identifier T _id in the reprocessing management table is the number of reprocessing times N _r
(The initial value is 0 at the start of processing), which is counted up for task _t1 . Since the reprocessing count Nr of task 1 is equal to the predetermined value 1, the link information T _lk between the waiting task and the task that causes the waiting is registered in the reprocessing management table, and task t ₁ , which is the waiting task, is placed in the waiting state W ₁ become. The following Table 1 shows the reprocessing management table at this time.

[Table] When the processing P _2o of the task t ₂ that caused the wait is completed, the link information T1k in the reprocessing management table in Table 1 is referenced again, and since there is a link, an event Iw is issued to the task t ₁ . . Task t ₁ is released from the waiting state W ₁ by event Iw, is activated, and performs reprocessing P _1r . By delaying the reprocessing in this manner, even if deadlock occurs during the processing as shown in FIG. 1, the processing is completed without repeating the deadlock and reprocessing. Figure 3 shows a second embodiment of the present invention with two tasks.
It shows the temporal flow of processing at t ₁ and t ₂ . Tasks t ₁ and t ₂ perform multiple file access processing P _1o and P _2o
When the deadlock state Dl occurs in the task _t1 , the automatic deadlock release process Bo is performed in the task _t1 . When the deadlock automatic release processing Bo is completed, the task identifier Tid in the reprocessing management table counts up the number of reprocessing times Nr (initial value 0 at the start of processing) for task _t1 . And the number of reprocessing times for task 1 Nr
is equal to the predetermined value 1, the link information Tlk between the waiting task and the task that causes the waiting is registered in the reprocessing management table, and the waiting task, task t ₁ , enters the waiting state W ₁ , and the timer processing task tx is ,
Issues the timer set event Is. The timer value at this time is determined by a random number. The following table −
2 shows the reprocessing management table at this time.

[Table] When the set time elapses, the timer processing task
Time-up event from tx to task t ₁
Ie is issued, the waiting state _W1 of the task _t1 is released, and the task t1 is activated to perform reprocessing _P1r . By delaying reprocessing in this way, the first
Even if a deadlock occurs during the process shown in the figure, the process is completed without repeating the deadlock and reprocessing. <Effects of the Invention> As explained above, the present invention can prevent deadlock from occurring due to exclusive control in resource units when multiple tasks access multiple file resources.
By delaying reprocessing, deadlock and repeated reprocessing can be avoided and processing throughput with multiple tasks can be increased.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the access order in a conventional data processing system in which a deadlock state and reprocessing are repeated, and FIG. ₂ is a diagram showing _a first embodiment of the present invention. FIG. 3 is a diagram showing the flow of the task, and is a second embodiment of the present invention.
FIG. 3 is a diagram showing the temporal flow of processing at t ₁ and t ₂ ; t ₁ , t ₂ : task, t _x : timer processing task, P _1o ,
P _2o : File access processing, Dl: Deadlock, Bo: Automatic deadlock release processing, W ₁ : Wait, Iw, Is, Ie: Event, P _1r : Reprocessing.

Claims (1)

[Claims] 1. A data processing system in which multiple tasks share multiple file resources to execute processing,
It is equipped with an exclusive control mechanism for each resource that has a deadlock detection mechanism for file resource sharing, and when it detects the occurrence of a deadlock state, this exclusive control mechanism outputs the data before the update as history information along with file updates so that backup can be performed. In a system equipped with an automatic deadlock release method, when a deadlock state occurs between tasks, backout processing is performed using the data before the update, the file is restored, and the resources occupied by the task are released. A reprocessing management table is provided to record the link information of the waiting task and the task causing the waiting task, and when a deadlock state occurs between tasks and the automatic deadlock release process is completed, the number of reprocessings in the reprocessing management table is counted up. , when this reprocessing count reaches a predetermined value, the link information of the waiting task and the task that causes the wait is registered, the waiting task is placed in the waiting state, and when the processing of the task that caused the wait is completed and the resources are released, the link information is registered. A delayed reprocessing method when a deadlock occurs, which is characterized by activating a waiting task based on information and causing it to perform reprocessing.