JPH0454662A - Exclusive access control system for shared resources - Google Patents

Abstract

PURPOSE:To improve the throughput by constituting the system so that when a certain processor accesses shared resources, a system bus is not locked but only the part which becomes an object of the access is locked. CONSTITUTION:As for shared resources 16 and 17, whether they are monopolized by a certain processor or not is managed by a control mechanism 18. Also, in resources 14, exclusive resources 44 which can be accessed from only a specific processor are provided. A control mechanism 18 and 19 control locking and unlocking of the resources 14 and 15, respectively. An access to the resources 16, 17 takes a form of an instruction 1 - updating - an instruction 2 such as read-out, updating, and write. That is, by a first instruction 1, the accessed part is locked, and by the instruction 2, locking is released. Therefore, the instruction 1 and the instruction 2 become an access with locking and an access with unlocking, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exclusive access control method for shared resources in a multiprocessor system comprising a plurality of processors and shared resources.

(Prior Art) In a multiprocessor system, a plurality of processors share resources such as a main storage device and a magnetic disk device. Such resources are called shared resources. Furthermore, in a multiprocessor system, when a certain processor uses a certain shared resource, the shared resource is prevented from being used by other processors. This is to prevent data stored in the shared resource from being destroyed. Such access to monopolize shared resources by a certain processor is called exclusive access.

FIG. 2 is a configuration diagram of a system to which a conventional shared resource exclusive access control method is applied.

The illustrated system consists of a plurality of processors 21, 22, 23 and resources 24, 25 connected to a system bus 20.

Processors 21, 22, 23 each access resources 24 or 25 via system bus 20. These processors 21.22.23 can access any of the resources 24 or 25.

The resources 24 and 25 consist of a main storage device, a magnetic disk device, or the like. Within resources 24 are shared resources 26 and 27. Whether or not shared resources 26 and 27 are monopolized by a certain processor is represented by a shared variable in another shared resource.

FIG. 3 is a flowchart showing a processing procedure for a processor to access a shared resource.

For example, a case where the processor 21 accesses the shared resource 24 will be described. First, the shared variable P of the shared resource 26. (step 531). This shared variable PD is stored within the shared resource 27. The shared variable Po is
For example, it consists of one bit of “O” or “l”, and “0”
indicates that the shared resource is not monopolized, and is "1'".

indicates that a shared resource is monopolized.

The monopolized state of the shared resource 26 is determined by the shared variable Po (step 532), and if it is not monopolized, the shared variable PD is rewritten to the monopolized state "l" (
Step 533). Thereafter, the processor 21 monopolizes the shared resource 26 and performs predetermined processing (step 534
) After this process is completed, the shared variable is returned to ○゛ (step 535).

At this time, it is assumed that the processor 21 and the processor 22 try to use the shared resource 26 at the same time. The processor 21 is
It reads the shared resource Po, detects that it is not monopolized, and rewrites the shared variable PD to "l" indicating that it is monopolized.

Immediately before the rewriting, the processor 22 uses the same shared variable P. , the processor 22 detects that it is not yet monopolized. Therefore, the processor 22 can also use the shared resource 26 at the same time as the processor 21 .

As a result, an access conflict occurs with respect to the shared resource 26, and data is destroyed.

To prevent such an access conflict from occurring, access from other processors is excluded from the time the shared variable is read until it is written again. For this reason, conventionally,
It monopolized system bus 2o. This is called bass lock.

Then, when writing of the shared resource is completed, the bus is unlocked. While the bus is locked, there are no other accesses to the shared resources, so there is no need to worry about access conflicts.

(Problems to be Solved by the Invention) However, the above-described conventional technology has the following problems.

That is, after the content of the shared variable is read by the processor 21 until it is updated, the other processors 22 and 23
I am in a state where I can't do anything. In other words, the conventional method of locking the entire system path 20 prohibits access to resources managed other than the specific shared variable PD, which not only increases the occupancy rate of the system bus 2o, but also The occupancy rate of resource 24.25 has become high.

Therefore, there is a problem in that data processing is not performed rationally and the throughput of the system is reduced.

The present invention has been made in view of the above points, and is an exclusive access control for shared resources that can reduce the occupation rate of the system bus and resources in order to prevent a decrease in system throughput due to exclusive access. The purpose is to provide a method.

(Means for Solving the Problems) The shared resource exclusive access control system of the present invention provides for a plurality of processors that each perform separate processing, a shared resource that is commonly used by the plurality of processors, and a shared resource that the processors When accessing the shared resource, the shared resource is characterized by comprising: a notification unit that notifies the shared resource of locking and unlocking; and a control mechanism that locks and unlocks the shared resource based on the notification from the notification unit. It is something to do.

(Operation) In the shared resource exclusive access control system of the present invention, when a processor accesses a shared resource, the notification means notifies the locking of the shared resource, and upon receiving this notification, the control mechanism only controls the shared resource. lock. In this state, the processor accesses the shared resource. After the access is completed, the notification means notifies the shared resource to be unlocked, and the control mechanism receives this notification and releases the lock.

Therefore, the system bus is not locked, resources can be used effectively, and system throughput is improved.

(Embodiment) FIG. 1 is a block diagram of an embodiment of a system to which the shared resource exclusive access control method of the present invention is applied.

The illustrated system consists of a plurality of processors 11.12.13, resources 14.15 and control mechanisms 18.19 connected to a system bus 10.

Processors 11, 12, 13 each access resources 14 or 15 via system bus 10. These processors 11.12.13 can access any of the resources 14 or 15. These processors 11.12.13 also have notification means 41.42.4.
It has 3.

The notification means 41, 42, 43 notifies the control mechanism 18 or 19 of locking or unlocking of the shared resource.

The resources 14 and 15 consist of a main storage device, a magnetic disk device, and the like. Since these resources 14, 15 are similar, only resource 14 will be described. Within resources 14 are shared resources 16 and 17. A control mechanism 18 manages whether the shared resources 16 and 17 are monopolized by a certain processor. Further, within the resources 14, there is a dedicated resource 44 that can only be accessed by a specific processor.

Control mechanisms 18 and 19 control locking and unlocking of resources 14 and 15, respectively. Since these have similar configurations, only the control mechanism 18 will be described.

The control mechanism 18 manages exclusive control of the resources 14. Access to shared resources 16.17 takes the form of instruction 1-update-instruction 2, such as read, update, write. The shared resource 16 or 17 being accessed between instruction 1 and instruction 2 must be locked.

That is, the first instruction 1 locks the accessed portion, and the instruction 2 unlocks it. Therefore, instruction 1 is access with lock, and instruction 2 is access with unlock.

FIG. 4 is a functional diagram of the control mechanism.

In the figure, ■ to ■ are inputs, and ■ to ■ are outputs.

■ notifies that the resource has been accessed.

■ indicates that the access of ■ is locked.

■ indicates that access to ■ is unlocked.

■ together with ■ notifies the address to be accessed. This address distinguishes whether the access is to the shared resource 16 or 17 or the dedicated resource 44. and,
Inside the control mechanism 18, it is stored whether each address is locked or unlocked.

■～■: (1) In the case of access to shared resources, and (
2) Perform the following response when accessing a dedicated resource.

(1) In the case of access to a shared resource, the response based on the relationship between the state of a certain address in the shared resource and the type of access that occurred at that time is as follows (a) to (d)
)become that way.

(a) When access with lock comes in the unlocked state, the access notification (■) is output and the device becomes locked.

(b) When an unlocked access is received in the unlocked state, an access notification (■) is output, and an error notification (■) is output.

(c) When access with lock comes in the locked state, ■
At the same time, the ``Access'' notification is output, and the ``Busy'' notification is output.

(d) When an unlocked access is received in the locked state, the access notification (■) is output and the device becomes in the unlocked state.

(2) When accessing a dedicated resource, the state of the address in the dedicated area is always the same,
When access is received, it only issues an acknowledgement.

FIG. 5 is a time chart showing the operation of the system according to the present invention.

In the diagram, access is indicated by ■~■, and transactions are indicated by ■~
Indicated by ■.

When the shared resource starting at address d is in the unlocked state and a read with lock is received (at the time of access marked ■ in Figure 5), the output is an acknowledgment (
Issue e). The shared resource is locked and the data in the shared resource is passed to the processor that accessed it (transaction@).

After that, even if a read with lock comes to the shared resource E starting at address e, the shared resource E can be accessed in the same way when accessing ■ (transaction ■).

When the shared resource starting at address d is in the locked state, if a read with lock comes (when accessing ■), an acknowledge (e) and a busy (f
). Since the processor at this time cannot read data from the shared resource, it retries.

When the shared resource is locked and a write with unlock is received (when accessing ■), an acknowledgment (e) is returned and data is written to the shared resource (transaction ■).
), the address d is unlocked and becomes unlocked.

When the shared resource is in the unlocked state, when access with unlock comes (when accessing ■), acknowledgment (
e) and error (g).

On the other hand, when accessing a dedicated resource, the processor occupying the resource can freely access data by issuing an acknowledgment as shown in FIG.

(Effects of the Invention) As explained above, according to the present invention, when a processor accesses a shared resource, it is possible to lock only the part to be accessed, instead of locking the system bus. Therefore, it has the following effects.

That is, the system bus can be used even while the resources are locked, and other processors can access unlocked portions of the resources. Therefore, the occupation rate of resources such as memory can be reduced. As a result, throughput can be improved and system performance can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of a system to which the shared resource exclusive access control method of the present invention is applied, FIG. 2 is a block diagram of a system to which the conventional shared resource exclusive access control method is applied, and FIG. The figure is a flowchart showing the processing procedure for accessing shared resources, FIG. 4 is a functional diagram of the control mechanism, and FIG. 5 is a time chart showing the operation of the system according to the present invention. O...System bus, 1.12.13...Processor, 4.15...Resource, 16.17...Shared resource, 8.
19...Control mechanism. : Shared variable: Not monopolized: Processing procedure for accessing monopolized shared resources Figure 3

Claims (1)

[Scope of Claims] A plurality of processors each performing separate processing, a shared resource commonly used by the plurality of processors, and when the processor accesses the shared resource,
An exclusive access control method for a shared resource, comprising: a notification unit that notifies the shared resource of locking and unlocking; and a control mechanism that locks and unlocks the shared resource based on the notification from the notification unit. .