JPH044441A - System for exclusively controlling memory - Google Patents

Abstract

PURPOSE:To avoid a conflict between exclusive requests by reading out the content of a flag and, when the content is 'used', canceling an exclusive request without rewriting the content of the flag. CONSTITUTION:When a processor 1(2) makes flag rewriting operation, the content of the flag is read out and whether the content is 'used' or 'not used' is confirmed. When the content is 'used', a process which cancels an exclusive request must be made instead of rewriting the content of the flag. Accordingly, a conflict between exclusive requests can be avoided, because a new exclusive request accepted by a memory device while another processor 2 (1) makes flag rewriting operation is eliminated by the processor which has issued the new request. Therefore, excellent control which avoids a conflict between exclusive requests can be performed even when rewriting operation is made on a flag incorporated in a memory device 3 or 4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an information processing system that includes a plurality of processors and executes multitask processing, in which the plurality of processors try to use the same memory device at the same time. The present invention relates to a memory exclusive control method that allows a specific processor that has notified an exclusive request to exclusively use the memory device when a specific processor receives an exclusive request.

[Prior Art 1] In an information processing system that executes multi-task processing, a conflict situation occurs in which multiple tasks try to use the same memory device on the system at the same time.As a memory control method in such a conflict, there is a A widely known method is to use semaphore flags.

For example, when one memory device is shared by multiple tasks, this method includes a flag that indicates whether the memory device is ``free'' or already ``in use.'' By preparing a semaphore flag (semaphore flag) and keeping the flag "in use" until the task that first made the usage request finishes using it, conflicting usage requests from subsequent tasks are eliminated. It is something to do.

When this method is adopted, the first task notifies the memory device of the usage request and changes the contents of the flag from “empty” to “”.
While the flag is being rewritten until it is rewritten to 'in use', it is necessary to prohibit other tasks from rewriting the same flag.

Otherwise, both tasks will mistakenly believe that the memory device is "free".

If the information processing system is a single-processor system, interrupts that involve task switching during a flag rewriting operation can be prohibited, but in a multiprocessor system, interrupts that involve task switching during a flag rewriting operation can be prevented. It is also necessary to prohibit processors from rewriting the same flag, and the conventional approach for multiprocessor systems is to have the processor executing the flag rewrite operation occupy the bus during the flag rewrite operation. measures have been developed.

However, although this countermeasure does exclude operations that rewrite the same flag in other processors, the problem is that the exclusion effect applies to all communications on the bus, resulting in a significant drop in system processing efficiency. was there.

Therefore, conventionally, the following method has been proposed as an improvement on this. This is a method in which, while a certain processor is performing a flag rewriting operation, the memory device containing the flag is occupied instead of occupying the bus.

In such a system, a mechanism is provided in the memory device to exclude all instructions from other processors when an exclusive request is received from the - processor, and the memory device stores the processor that first issued the exclusive request. Thereafter, the processor does not accept any access to its own memory device from other processors until that processor releases the exclusive request.

[Invention or Problem to be Solved] However, even with this conventional method, during the flag rewriting operation,
Since the memory device is completely occupied by one processor, processing efficiency is often reduced, and in today's era of rapid integration of memory semiconductor devices, this is not a satisfactory solution, and furthermore, it is not a satisfactory solution. The development of a new memory control method that has less impact on processing efficiency has been awaited.

The present invention has been made in view of the above circumstances, and in an information processing system that includes a plurality of processors and executes multitask processing, when a plurality of processors try to use the same memory device at the same time, Memory exclusive control is a memory exclusive control method that allows a specific processor that has notified an exclusive request to use the memory device exclusively, and is capable of reducing a decrease in system processing efficiency due to monopolization of the memory bus or memory device. The purpose is to provide a method.

[Means for Solving the Problems] A memory exclusive control method according to the present invention provides an information processing system that includes a plurality of processors and executes multitask processing, in which the plurality of processors access the same memory device at the same time. , the specific processor that has notified the exclusive request is granted exclusive use of the memory device.

Specifically, the memory device is provided with an exclusive control circuit that performs certain processing in response to an exclusive request from a processor.

Then, is this exclusive control circuit already in an "in use" state where it is already in exclusive operation and cannot receive new exclusive requests, or is it in an "empty" state where it can receive new exclusive requests? A flag indicates whether it exists.

Further, when the exclusive control circuit receives a new exclusive request, if the flag is set to ``busy'', the exclusive control circuit notifies the processor that issued the exclusive request of an abnormal acceptance, and if the flag is ``empty'' The configuration is such that the processor that issued the exclusive request is notified of normal acceptance.

On the other hand, each processor sharing the memory device is caused to perform the following processes (i) to (iii) as exclusive control processing when an exclusive request is notified to the memory device.

(1) First, the exclusive control circuit monitors whether the reception is normal or abnormal, and if the reception is abnormal, the access to the memory device is restarted from the beginning.

(ii) If the reception is normal, read the contents of the flag and check whether it is "in use" or "free", and if it is in use, release the exclusive request and then use the memory device. Retry access from the beginning.

(iii) On the other hand, if the memory device is empty, in order to cause the exclusive control circuit of the memory device to perform an exclusive operation,
A process of rewriting the contents of the flag is executed, and when the rewrite process is completed, the memory device is notified of cancellation of the exclusive request.

With the above-mentioned processor and memory device, if the access from the processor to the memory device is of a type that does not involve an exclusive request, the access will be normally accepted even if the flag of the memory device is "Paper in use". and perform the access.

[Operation] The memory exclusive control method according to the present invention equips a memory device with a flag, and depending on whether the display content of this flag is “in use” or “empty”, it is determined whether the memory device is already in exclusive operation. When the display content of the flag is "in use", that is, when an exclusive request is received from the processor while the exclusive operation is already in progress, the memory device Conflicts between exclusive requests are avoided by notifying the processor that issued the exclusive request of abnormal reception.

Furthermore, when the flag of the memory device is ``empty'', that is, when a new exclusive request is received from a processor or source when the exclusive operation is not yet in progress, the new exclusive request is accepted by the memory device. is attached, and the flag rewriting operation is performed by the processor that issued the exclusive request, but in this case, another processor that issued the exclusive request before that has already rewritten the flag. It may be in operation.

However, in the memory exclusive control method according to the present invention, when the processor performs a flag rewriting operation, the content of the -8= flag is read and it is checked whether the content is "in use" or "free". If the flag is "in use", it is mandatory to release the exclusive request without rewriting the contents of the flag, so if the memory device is not being accepted while another processor is rewriting the flag. Conflicts can be avoided by eliminating new exclusive requests through the processing of the processor itself that issued the new exclusive requests.

Therefore, the memory exclusive control method according to the present invention provides good control to avoid conflicts between exclusive requests not only during the exclusive operation of the memory device but also during the rewriting operation of the flag installed in the memory device. obtain.

Moreover, since the memory exclusive control method according to the present invention performs exclusive control using the processing of the processor itself or the flag of the memory device, exclusive control can be performed without occupying the memory bus. Even during a flag rewrite operation, if the access from another processor to the memory device does not involve an exclusive request, the access can be normally accepted and executed. Compared to the memory exclusive control method, it is possible to significantly reduce the decrease in system processing efficiency due to the occupancy of the memory bus or memory device.

[Embodiment] FIG. 2 shows the device configuration of an information processing system that implements an embodiment of the present invention.

This information processing system is equipped with a plurality of processors and executes multitask processing, with a code ratio of 2 being a processor (CPU) and a code ratio of 3.4 being a memory device (MEM).

The memory devices 3 and 4 are shared by the two processors 1 and 2, and these memory devices and the processors are connected by various bus lines 7.

Here, the bus line 7 is connected to the address/data line (AD line) 8.
, tag line (TAG line) 9, status line (STS line) 1
01 and other bus lines (not shown).

The address/data line 8 is a signal line through which addresses and data are multiplexed and sent when the processor 1-2 accesses the memory devices 3, 4.

The tag line 9 is a signal line that indicates the type of memory access, and is used for various commands such as read, write, and exclusive requests, and for notification of read responses.

When the memory device 3 or the memory device 4 is accessed from the processors 1 or 2, the status line 10 indicates whether the memory device 3 or the memory device 4 has accessed the processor as “normal reception” or “abnormal reception”. ” response signal.

The memory exclusive control method of this embodiment makes an exclusive request when processors 1 and 2 try to use the same memory device 3 (or memory device 4) at the same time in the information processing system shown in FIG. This allows one of the processors that has notified to use the memory device 3 (or memory device 4) exclusively, and the memory devices 3 and 4 and each processor 1 and 2 are devised for exclusive control. .

Below, these devised configurations and their functions and effects will be explained in detail.

The memory devices 3 and 4 are provided with an exclusive control circuit 5 that performs certain processing in response to an exclusive request from the processor 1 or 2. .10 is connected.

The exclusive control circuit 5 determines whether its own memory device is already in an exclusive operation and is in the "in use" state where it cannot receive a new exclusion request, or whether it is in the "in use" state where it can receive a new exclusion request. A flag (semaphore flag) indicates whether the memory is in a free state.

In FIG. 2, reference numeral 6 indicates an exclusive operation display flip-flop that functions as this flag, and this flip-flop 6 is reset when the system is reset.

Further, the exclusive control circuit 5 monitors the communication on the bus 7 mentioned above during system operation, and there is an indication of an exclusive request on the tag line 9, and the memory address on the address/data line 8 is If it is in the own memory device, this is accepted as an exclusive request to the own memory device. Then, when a new exclusive request is received, if the flag set by flip-flop 6 is already in use,
Notifies the processor that issued the exclusive request of the abnormal reception,
If the flag is "vacant", the processor that issued the exclusive request is notified of normal acceptance.

If the exclusive request is successfully accepted, the flag is rewritten by the processor that issued the exclusive request, and the flag display is set to Pa in use. The display will be reset.

When the flag by the flip-flop 6 indicates that the memory device is in use, the memory devices 3 and 4 do not accept a new exclusive request by outputting an abnormal acceptance to the status line 10. , general accesses that are not accompanied by exclusive requests are accepted and a predetermined response is made.

On the other hand, when each of the aforementioned processors notifies the memory device 3 (or memory device 4) of an exclusive request, the first
Execute the exclusive control process shown in the figure.

That is, first, the processor (1) notifies the memory device of an exclusive request and a flag address, and (ii) changes the status line 10 of the memory device corresponding to the notified flag address.
If an abnormal reception is detected (that is, if the memory device is already in exclusive operation), the processes (i) and (ii) are repeated (step 11).

If a normal reception is detected by checking the response signal on the status line 10 (that is, if the memory device is not yet in exclusive operation), the processor issues a flag data transfer request to the notified flag address. (Step 12).

Then, when the memory device returns a response to the read request and flag data to the processor (step 13), the processor determines the display content of the flag from the flag data (step 14). The process advances to step 15, and if it is "in use", the process advances to step 17.

In step 15, the processor rewrites the display content of the semaphore flag to "in use."

After completing the process in step 15, the processor cancels the exclusive operation on the memory device that made the exclusive request,
The process ends (step 106).

On the other hand, if it is determined in step 14 that the memory device is in use, the process proceeds to step 17. In step 17, the exclusive operation is canceled for the memory device that notified the exclusive request, and the memory device is reset again. , repeat the process from step 11.

In the above configuration, for example, when the processor 1 issues an exclusive request to the memory device 3 and the display content of the flag of the memory device 3 is rewritten to "in use" by the exclusive request, that is, When the memory device 3 is already under exclusive operation by the processor 1, when the processor 2 issues an exclusive request to the memory device 3, the memory device 3 notifies the processor 2 that issued the exclusive request of abnormal acceptance. , conflicts in exclusive requests are avoided.

Furthermore, when the flag of the memory device 3 is “empty °”,
That is, when the processor 2 issues a new exclusive request to the memory device 3 while the memory device 3 is not yet in exclusive operation, the new exclusive request is accepted by the memory device 3 and the exclusive request is not accepted. The flag rewriting operation will be performed by the processor 2 that issued the flag, but in this case, the processor 1 has already issued an exclusive request to the memory device 3 and the flag rewriting operation is being performed by the processor 1. It may be.

However, as mentioned above, in exclusive control processing of each processor, when a processor performs a flag rewriting operation, it is necessary to read the contents of the flag and check whether the contents are "in use" or "free". Step 14 of checking is incorporated, and further step 1 of canceling the exclusive request without rewriting the contents of the flag if it is "used °'".
7, processor 2 is inserted into memory device 3 while processor 1 is rewriting the flag.
The new exclusive request will be eliminated by exclusive control processing of the processor 2 itself, and conflicts will be avoided.

Therefore, in the memory exclusive control method according to this embodiment,
Good control can be performed to avoid conflicts of exclusion requests not only during the exclusive operation of the memory device but also during the rewriting operation of the flag installed in the memory device.

Moreover, since the memory exclusive control method of this embodiment performs exclusive control using the processing of the processor itself or the flag of the memory device, exclusive control can be performed without occupying the memory bus. Even during operation or during a flag rewriting operation, if an access from another processor to the memory device does not involve an exclusive request, the access can be normally accepted and executed. Compared to the memory exclusive control method described above, it is possible to significantly reduce the decrease in system processing efficiency due to the occupancy of the memory bus or memory device.

U Effects of the Invention As is clear from the above explanation, the memory exclusive control method according to the present invention equips a memory device with a flag and determines whether the display content of the flag is "used" or "free". This indicates whether the memory device in question is already in exclusive operation or not, and when the display content of the flag is 'in use', that is, when the memory device is already in exclusive operation, When a request is received, the memory device notifies the processor that issued the exclusive request of the abnormal reception to avoid conflicts of exclusive requests.

In addition, when the flag of the memory device is "empty", that is, when a new exclusive request is received from the processor when the exclusive operation is not yet in progress, the new exclusive request is not accepted by the memory device. The flag rewriting operation will be performed by the processor that issued the exclusive request, but in this case, another processor that issued the exclusive request before that may already be in the process of flag rewriting. be.

However, in the memory exclusive control method according to the present invention, when the processor performs a flag rewriting operation, it reads the contents of the flag, checks whether the contents are "in use" or "free," and If it is "medium", it is mandatory to release the exclusive request without rewriting the contents of the flag, so a new exclusive request received by the memory device while another processor is rewriting the flag is required. can be eliminated by the processor itself that issued the new exclusive request to avoid conflicts.

Therefore, the memory exclusive control method according to the present invention provides good control to avoid conflicts between exclusive requests not only during the exclusive operation of the memory device but also during the rewriting operation of the flag installed in the memory device. obtain.

Moreover, the memory exclusive control method according to the present invention is not limited to the processing of the processor itself or the 711 group of the memory device. Since this is exclusive control, it is possible to perform exclusive control without occupying the memory bus, and furthermore, even during exclusive operation or flag rewrite operation, other processors cannot access the memory device. When the access is of a type that does not involve an exclusive request, the access can be accepted and executed normally, so compared to the conventional memory exclusive control method, system processing efficiency is improved by occupying the memory bus and memory device. can significantly reduce the decrease in

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the processing procedure of an embodiment of the present invention, and FIG. 2 is a block diagram of a system that executes the embodiment. ■, 2... Processor, 3, 4... Exclusive control circuit, 6... Flip-flop for exclusive operation display, 7... Bus line, 8... ...Address/data line, 9...Tag line, 10...
・Status line.

Claims (1)

[Claims] In an information processing system that includes multiple processors and executes multitask processing, when multiple processors attempt to use the same memory device at the same time, a specific processor that has notified an exclusive request The memory device is provided with an exclusive control circuit that performs certain processing in response to an exclusive request from a processor, and the exclusive control circuit allows exclusive use of the memory device. , displays a flag to indicate whether the device is already in an exclusive state and cannot receive new exclusive requests, or is in a free state, and can receive new exclusive requests. When an exclusive request is received, if the flag is "in use", the processor that issued the exclusive request is notified of an abnormal reception, and if the flag is "free", the processor that issued the exclusive request is notified of normal acceptance. On the other hand, when each processor sharing the memory device is notified of an exclusive request to the memory device, the exclusive control circuit first determines whether to accept normally or abnormally. If the reception is abnormal, the access to the memory device is restarted from the beginning, and if the reception is normal, the contents of the flag are read and the flag is determined to be "in use" or "free."
If the memory device is in use, the exclusive request is canceled and the access to the memory device is restarted from the beginning. If the memory device is empty, the exclusive control circuit of the memory device is In order to perform an exclusive operation, the content of the flag is rewritten, and when the rewriting process is completed, the memory device is notified of the release of the exclusive request, and the access from the processor to the memory device is of a type that does not involve an exclusive request. 1. A memory exclusive control method characterized in that when the memory device is used, the access is normally accepted and the access is executed even if the flag of the memory device is "in use".