JPH04262425A - Exclusive control system for commonly shared resource - Google Patents

Abstract

PURPOSE:To upgrade an efficiency of using a commonly shared resource by reducing lock waiting time for a successive lock waiting task. CONSTITUTION:When a task locks a resource and the task terminates the execution of a lock right, a lock priority setting means 4 sets up as a lock priority for a relevant task a value calculated from a function f(x) where values a and b are present that have a relation of a>b that satisfies f(a)>=f(b) with respect to variable x of resource in the lock of the relevant task and also from a function f(x) where values c and d are present that have a relation of c>d that satisfies f(c)>f(d) with respect to variable x of resource in the lock of the relevant task. Further, when a task becomes ready for lock waiting, a lock sequency change means 3 changes a lock queue so that a lock right transfer sequence to a lock waiting task becomes higher in lock priority.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shared resource exclusive control method in a computer system.

0002

2. Description of the Related Art In a computer system, exclusive control is required for resources (shared resources) used by a plurality of tasks in order to serialize access to them.

For such exclusive control, electronic computer systems are equipped with basic functions called lock/unlock or ENQ (enqueue)/DEQ (dequeue). Note that there are two types of lock requests: exclusive mode and shared mode.

The basic operation of exclusive control is performed as follows.

[0005] When a task issues a lock request, the resource for which the lock request is made is not locked by another task, or the lock mode of the resource and the mode of the lock request of the task are both shared mode. is immediately granted lock rights to the requested task.

However, if the resource is locked and either the lock mode of the resource or the lock request mode of the task is exclusive mode, the task is placed in a lock wait state.

On the other hand, when a task that has locked a resource issues an unlock request after finishing using the resource, that task's exercise of locking rights ends.

[0008] In this case, if the task that issued the unlock request has locked the lock in exclusive mode, if there is a task that is waiting, even if the request mode of the task that requested the lock earliest is exclusive mode. For example, the lock right is granted only to that task, and if the task is in shared mode, the lock right is granted to all tasks currently waiting for a lock in shared mode.

[0009] Furthermore, if the task that issued the unlock request holds the lock in shared mode, if there is a task in exclusive mode that is waiting, that task is given the locking right.

[0010] Note that if there is no task waiting at the time the unlock request is made, the lock right is not granted, as a matter of course.

[0011]

[Problems to be Solved by the Invention] As mentioned above, in the conventional shared resource exclusive control method, when multiple resources are used and processed simultaneously, lock requests are made for each resource sequentially, but some If a resource is successfully locked and the task is placed in a lock wait state when attempting to lock the next resource, the waiting time of other tasks that are already waiting to lock the resource that the task has already locked becomes unnecessarily long, and the resource The disadvantage was that the usage efficiency of

[0012] In such a case, it can be solved by applying an all-or-nothing technique in which no resources are secured unless all the necessary resources are secured, but this will complicate control and affect processing performance. It is not desirable because it gives

The present invention has been proposed in view of the above points, and its purpose is to reduce the lock waiting time of subsequent lock waiting tasks and improve the efficiency of using shared resources. The purpose of this invention is to provide a resource exclusive control method.

[0014]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a lock priority for each task in a shared resource exclusive control method of a computer system, When the task finishes exercising the locking right, there exists a and b such that f(a)≧f(b) holds true for the number of locked resources x of the task, and f(c)>f (d) holds, c > d,
lock priority setting means for setting a value calculated by a function f(x) where d exists as the lock priority of the task; and a lock priority setting means for setting a value calculated by a function f(x) where The lock order changing means rearranges the lock queue in order of lock priority.

[0015]

[Operation] In the shared resource exclusive control method of the present invention, when a task locks a resource and when a task finishes exercising the locking right, the lock priority setting means sets the number of locked resources of the task. For x, there exist a and b such that f(a)≧f(b) holds, and f(c)>f(d
) holds true, c > d, and there exists a function f(x)
The value calculated by is set as the lock priority of the task, and when the task becomes a lock waiter, the lock order changing means sets the lock so that the order in which lock rights are granted to tasks waiting for a lock is in descending order of lock priority. Reorder the queue.

[0016]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the shared resource exclusive control system of the present invention.

In FIG. 1, the shared resource exclusive control mechanism 7 includes a lock request processing means 1 for processing lock requests, an unlock request processing means 2 for processing unlock requests, and locks in descending order of lock priority. A lock order changing means 3 for rearranging the queue, a lock priority setting means 4 for setting a value calculated by a predetermined function from the number of locked resources of the task as the lock priority of the task, and an exclusive control table 5. , and a lock priority table 6.

FIG. 2 shows the logical configuration of the exclusive control table 5 and the lock priority table 6.

In other words, the exclusive control table 5 uses resource names as keys to uniquely identify resources subject to exclusive control within the system, and entries for each resource include a resource name section and a lock mode section. , a locked task list, and a lock queue. here,
The lock mode section records the lock mode when the resource is locked, and the locked task list records the task identifier of the task that locks the resource.
The lock queue is a queue of waiting lock requests, and records the task identifier and lock mode pairs of the tasks issuing these requests. Note that the lock mode is expressed as "S" for shared mode and "E" for exclusive mode.

The lock priority table 6 uses a task identifier as a key, and the entry for each task is composed of a task identifier section, a number of locked resources section, and a lock priority section. Here, the number of locked resources section records the number of resources locked by the task, and the lock priority section records the lock priority of the task.

The operation of each processing section will be explained below.

(1) Lock request processing means 1 When a lock request is made from any of the tasks T1 to Tn, the lock request processing means 1 processes the lock request.

That is, the lock request processing means 1 refers to the entry corresponding to the requested resource in the exclusive control table 5, and if the lock mode section is empty, or the lock mode of the request and the value of the lock mode section are If both are in shared mode S, the lock mode of the request is recorded in the lock mode section, and the task identifier of the task that issued the request is added to the locked task list.

Next, after adding 1 to the number of locked resources section of the entry for the task that issued the lock request in the lock priority table 6, the lock priority setting means 4 is called using the task identifier of the task as a parameter.

On the other hand, when a lock request is made from tasks T1 to Tn, if the lock mode field corresponding to the requested resource in the exclusive control table 5 is not empty and the lock request of the task is in exclusive mode E, or If the value of section is exclusive mode E, add the task identifier and lock mode pair of that task to the end of the lock queue,
Call the lock order changing means 3.

Next, the processing of the task that issued the request is interrupted.

(2) Unlock request processing means 2 When an unlock request is made from any of the tasks T1 to Tn, the unlock request processing means 2 processes the unlock request.

That is, the unlock request processing means 2 deletes the task identifier of the task that issued the unlock request from the locked task list of the corresponding resource entry in the exclusive control table 5, and After subtracting 1 from the number of locked resources in the task entry, the lock priority setting means 4 is called using the task identifier of the task as a parameter.

Next, if the locked task list in the exclusive control table 5 is empty, the lock mode section is deleted.

Furthermore, if there is a task waiting for a lock in the lock queue of the exclusive control table 5, and the next task waiting for a lock requests a lock in exclusive mode E, the exclusive mode E is set in the lock mode field. The task identifiers of the tasks are recorded in the task list, and the task identifiers, etc. of the tasks are deleted from the lock queue.

Furthermore, if the next task waiting for a lock is requesting a lock in shared mode S, the shared mode S is recorded in the lock mode section, and all the tasks in the lock queue that have issued a lock request in shared mode are The task identifier of the task,
It is recorded in the locked task list and all shared mode task identifiers etc. in the lock queue are deleted.

Next, for the tasks with all the task identifiers recorded in the locked task list, 1 is added to the number of locked resources in the lock priority table 6, and the lock priority changing means 4 assigns the task to each task using each task identifier as a parameter. After a few minutes of repeated calls, these tasks will resume processing.

(3) Lock order changing means 3 The lock order changing means 3 operates when called by the lock request processing means 1 with the task identifier of the task placed in the waiting state as a parameter.

That is, the lock order changing means 3 refers to the lock priority section of the lock priority table 6 in the lock queue of the exclusive control table 5, and sorts the lock queue in the order of the lock priority of the task that issued each request. Sort. At this time, lock requests from tasks with the same lock priority are arranged on a first-come, first-served basis.

(4) Lock priority setting means 4 The lock priority setting means 4 calls the task identifier of the task whose number of locked resources has been changed from the lock request processing means 1 or the unlock request processing means 2 as a parameter. It works when the

That is, the lock priority changing means 4 calculates the lock priority by referring to the number of locked resources for the entry for the task identifier specified by the parameter of the lock priority table 6, and changes the value to the corresponding lock priority. Record in the lock priority section of the entry. Calculation of lock priority is based on the number of locked resources x, there exists a and b such that f(a)≧f(b) holds, and f(c)>f(d) holds. A function f(x) with c and d such that c>d is used. For example, f(x)=x and the number of locked resources itself can be used as the lock priority.

Next, the specific operation of this embodiment will be explained with reference to FIGS. 3 to 7.

FIG. 3 is a timing chart showing a situation in which four tasks T1 to T4 sequentially issue lock requests and unlock requests to two resources R1 and R2.

FIGS. 4 to 7 show each time ta in FIG.
The states of the exclusive control table 5 and the lock priority table 6 at ~td are shown. Note that before time t,
It is assumed that resources R1 and R2 are not locked.

In addition, a function f(x) such that f(0)<f(1)<f(2) holds is used, and the number of locked resources and lock priority part of the lock priority table 6 are are initialized to "0" and "f(0)", respectively.

When task T1 requests to lock resource R1 in exclusive mode E at time t, lock request processing means 1 is called, and since resource R1 is not locked, task T1
1 is granted a lock right, exclusive mode "E" is recorded in the lock mode section of the exclusive control table 5, and task identifier "T1" is recorded in the locked task list.

[0043] Also, the task T of the lock priority table 6
"1" is added to the number of locked resources section of 1, the lock priority setting means 4 is called, and "f(1)" is set in the lock priority section of task T1.

When task T2 requests to lock resource R1 in exclusive mode E at time t+1, lock request processing means 1 is called, and since resource R1 is already locked in exclusive mode E, task T2 waits for a lock. A pair “T2, E” of task identifier T2 and exclusive mode E is recorded in the lock queue of the exclusive control table 5.

Subsequently, the lock order changing means 3 is called and the lock queue of the exclusive control table 5 is rearranged, but this is essentially meaningless since the only task waiting for the lock at this point is T2. After this, the processing of task T2 is interrupted and enters a wait state.

At time t+2, task T3 requests to lock resource R2 in shared mode S, and at time t+3, task T4 requests to lock resource R2 in exclusive mode E, task T1
, T2, the lock right is granted to task T3, and task T4 waits for the lock. As a result, the exclusive control table 5 and lock priority table 6 at time ta are in the state shown in FIG. 4.

When task T3 requests to lock resource R1 in shared mode S at time t+4, lock request processing means 1 is called, and since resource R1 is already locked in exclusive mode, the lock queue of exclusive control table 5 is At the end, a pair "T3,S" of task identifier T3 and shared mode S
will be added.

Next, the lock order changing means 3 is called, and the lock priorities of tasks T2 and T3 are respectively f.
(0), f(1), and since f(0)<f(1), the lock queue is rearranged in the order of task T3's lock request, task T2's lock request, and then task T3's lock request. Processing is interrupted and the system enters a waiting state. In other words, task T3 overtakes task T2, which requested the lock first, and
Priority is given to granting the lock right to task T3. As a result,
At time tb, the exclusive control table 5 and lock priority table 6 are in a state as shown in FIG.

When the task T1 requests (U) to unlock the resource R1 at time t+5, the unlock processing means 2 is called and the task identifier T1 is deleted from the locked task list of the exclusive control table 5.

Subsequently, "1" is subtracted from the number of locked resources of task T1 in the lock priority table 6, and the lock priority setting means 4 uses the task identifier T1 as a parameter.
is called, and “f(0
)” is set. As a result, the locked task list in the exclusive control table 5 becomes empty, and the lock mode section is also erased.

Furthermore, since the lock queue is not empty,
A lock right is granted to the first lock requesting task T3, a shared mode S is recorded in the lock mode section, and a task identifier T3 is recorded in the locked task list.

Next, "1" is added to the number of locked resources section of the task T3, the lock priority setting means 4 is called with the task identifier T3 as a parameter, and "f(2) is added to the lock priority section of the task T3. )” is set, task T
The process of step 3 is restarted. As a result, the exclusive control table 5 and lock priority table 6 at time tc are in a state as shown in FIG.

[0053] At time t+6, task T3 uses resources R1 and R2.
When an unlock request is subsequently made, the same processing as the unlock request by task T1 is performed, and the lock right is granted to task T2 for resource R1 and to task T4 for resource R2. As a result, the exclusive control table 5 and lock priority table 6 at time td are in a state as shown in FIG.

In the above example, f(0)<f(1)<f(
2), but for a<b, f(a)=f
A function f(x) as shown in (b) can also be used, which is advantageous in an environment where it is considered better to process on a first-come, first-served basis when the number of locked resources is not significantly different. In this case, the operation is the same except that when the lock order changing means 3 rearranges the lock queue, the task with the number of locked resources b is not prioritized over the task with the number of locked resources a, but is arranged on a first-come, first-served basis. This will be the process.

[0055] Furthermore, when the number of locked resources itself is taken as the lock priority, f(0)<f(1)<...<f(n)
<f(n+1)<..., so if the numbers of locked resources for tasks Ta and Tb are a and b, respectively, then a>
If b, the lock request of task Ta always takes priority over the lock request of task Tb.

[0056]

Effects of the Invention As explained above, in the shared resource exclusive control method of the present invention, a lock priority is introduced that increases as the number of locked resources increases, and a task with a high lock priority is However, by controlling tasks such that locking rights are given priority to tasks with lower locking priority,
When a task that has already locked some resources requests a lock on a new resource and becomes locked, the lock waiting time can be reduced. This has the effect of reducing the lock waiting time of other tasks, and improving the efficiency with which shared resources are used.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of a shared resource exclusive control method of the present invention.

FIG. 2 is a diagram showing the logical configuration of an exclusive control table and a lock priority table in FIG. 1;

FIG. 3 is a timing chart for explaining a specific example.

FIG. 4 is a diagram showing an example of the states of an exclusive control table and a lock priority table.

FIG. 5 is a diagram showing an example of the states of an exclusive control table and a lock priority table.

FIG. 6 is a diagram showing an example of the states of an exclusive control table and a lock priority table.

FIG. 7 is a diagram showing an example of the states of an exclusive control table and a lock priority table.

[Explanation of symbols]

1……Lock request processing means 2...Unlock request processing means 3………Lock order changing means 4. Lock priority setting means 5......Exclusive control table 6...Lock priority table 7...Shared resource exclusive control mechanism T1~Tn...Task R1, R2...Resources

Claims (2)

[Claims] [Claim 1] In a shared resource exclusive control method for a computer system, a locking priority is set for each task, and when a task locks a resource, when a task finishes exercising the locking right, and when the task is currently locked. For each number x of resources, there exist a and b such that a>b such that f(a)≧f(b) holds, and there exist c and d such that c>d such that f(c)>f(d) holds. a lock priority setting means that sets a value calculated by a function f(x) as the lock priority of the task; and when a task becomes lock wait, the lock priority is set in the order in which lock rights are granted to the lock waiting task. 1. A shared resource exclusive control method comprising: lock order changing means for rearranging lock queues in descending order of lock queues. 2. The shared resource exclusive control system according to claim 1, wherein f(x)=x.