JPS6285372A - Comparing and swapping system in multi-processor system - Google Patents

Abstract

PURPOSE:To execute exclusive control by a comparing and swapping system,by controlling whether a rewriting processing of data which has been stored in a prescribed area can be executed or not, in accordance with a result of comparison of a comparing means. CONSTITUTION:A processor 1 which is not shown in the figure stores an address of a counting type semaphore in an address holding means 27 through a signal line 121, and also stores write data in a write data holding means 26 through a signal line 122. A decoding means 20 sends out a write instruction through a signal line 201 to a common storage device 5 which is not shown in the figure, and also sends out a write address through a signal line 252, and the write data through a signal line 253 from the means 27 and the means 26, respectively. As for the write instruction of the signal line 201, AND is taken with a result of comparison of the means 25 on a signal line 251 in an AND circuit 28, and a logical signal is sent out to a signal line 281. Accordingly, only when an output of the means 25 is '1', rewriting of the counting type semaphore of the device 5 is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a shared memory access method in a multiprocessor system, and particularly to a compare and swap method.

[Conventional technology]

Generally, in a multiprocessor system in which a storage device is shared by multiple processors, exclusive control is performed to prevent multiple processors from simultaneously and unconditionally accessing shared resources on the shared storage device.

Various types of exclusive control methods are known, but
One of them is a method called the conveyor and swamp method. This method attempts to utilize certain resources on a shared storage device.

First, data of a fixed byte length (usually a 4-byte or 8-byte area (shared storage area)) starting from a specified address on the shared storage device and comparison data of the same byte length prepared by the own processor are If they match, it is determined that access by the own processor is possible, and the contents of the shared storage area are rewritten with write data of the same byte length to prohibit access to the same resource from other processors. This method prevents rewriting if the data in the shared storage area is not read and rewritten.Since access to the shared storage area by other processors is prohibited between the read operation and the rewrite operation of the shared storage area, the data in the shared storage area is Rewriting is limited to only one processor.Whether or not the rewriting to the shared storage area was successful can be determined by the program using condition codes, etc., and only if it is successful, the system resources are referenced and updated, and then , exclusive reference to system resources by returning the data in the shared storage area that has been rewritten by the compare-and-swap function to its original value.

Achieving updates.

[Problem that the invention seeks to solve]

By the way, in the conventional compare-and-swap method mentioned above, the byte length of the data to be compared is fixed, so
The compare-and-swap method cannot be applied if there are fields within the fixed byte length for which comparison data cannot be created, and is only applicable in limited cases where all fields of comparison data can be created. It had the notable drawback of not being able to do so.

An example in which all fields of comparison data cannot be created is, for example, a case where a counting type semaphore 90 of the format shown in FIG. 3 is stored in a coexisting storage area. This counting type semaphore 90 is composed of fields of a semaphore count value 901 and a last semaphore user process identification name 902, and if it must be exclusively referenced and updated, the semaphore count value 901 is the field of the semaphore. Normally, when it is not used by a process, the value is "0", so the semaphore count value is 9 in the comparison data.
Although a field corresponding to 01 can be created, the value of the semaphore using process identification name 902 is generally unpredictable. Therefore, in such a case, the compare and swap method cannot be used.

An object of the present invention is to enable exclusive control using the compare-and-swap method even when there are fields for which comparison data cannot be created.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a system for processing data stored in a predetermined area on the shared storage device and the own processor when accessing coexisting resources on a coexisting storage device shared with another processor. The shared resource is accessed by comparing the comparison data with prepared comparison data and rewriting the data stored in the predetermined area with predetermined data of the own processor only when a predetermined comparison result is obtained. In a compare-and-swap method in a multiprocessor system, the present invention further comprises a comparison mask data holding means for storing comparison mask data indicating a field to be compared between data stored in the predetermined area and comparison data prepared by the own processor; , a comparison means for comparing the data stored in the predetermined area and the comparison data prepared by the own processor according to the content of the comparison mask data held in the comparison mask data holding means, the comparison means The configuration is configured to control whether or not the rewriting process of the data stored in the predetermined area can be executed according to the comparison result.

[Effect]

If you cannot create all fields for comparison data,
If comparison mask data that masks fields that cannot be created is stored in the comparison mask data storage means, that field will be excluded from comparison, and the data stored in the shared storage area will be stored only in accordance with the comparison results of other fields. You can control whether or not the rewriting process can be executed.

〔Example〕

FIG. 2 is a block diagram showing an embodiment of the multiprocessor system of the present invention. This multiprocessor system consists of two processors 1 and 3, two shared memory access control units 2.4, and a shared storage device 5. Signal lines 120 to 123 are used to connect the processor 3 and the shared memory access control unit 4, signal lines 340 to 343 are used to connect the shared memory access control unit 2 and the shared storage device 5, and signal lines 250 are used to connect the shared memory access control unit 2 and the shared storage device 5.
~253°520, signal lines 450 to 453,540 are connected between the shared memory access control unit 4 and the shared memory device 5, and signal lines 240,420 are connected between the shared memory access control unit 2 and the shared memory access control unit 4, respectively. It is connected.

FIG. 1 is a block diagram of an embodiment of the shared memory access control section 2, and the shared memory access control section 4 can also have a similar configuration. As shown in the figure, this shared memory access control section 2 includes a decoding means 20, an access prohibiting means 21, a successive data holding means 22, a comparison data holding means 23, a comparison mask data holding means 24, and a comparison mask data holding means 24. It is composed of means 25, write data holding means 26, address holding means 27, and AND circuit 28. Here, the address holding means 27. Write data holding means 2
6. Comparison data holding means 23. Read data holding means 2
2 consists of registers each having a width of 4 bytes, and the comparison mask data holding means 24 consists of a total of 4-bit registers in which 1 bit corresponds to each 1 byte of the 4-byte registers, and corresponds to the bytes to be actually compared. The value "1" is set to the bit that corresponds to the byte to be compared, and the value "0" is set to the bit corresponding to the byte that is not compared.

Next, the operation of this embodiment will be explained using an example in which the processor 1 in FIG. 1 accesses the shared storage device 5. still,
The data in the shared storage device 5 to be compared and swapped is the counting type semaphore 90 shown in FIG. 3, and the semaphore count value 901. Last semaphore user process identification name 90
2 are both 2 bytes.

First, the processor 1 sends the address of the counting semaphore 90 to the address holding means 27 via the signal line 121, and sends the signal !
122 and write data holding means 2.
6, the comparison data (hexadecimal number ro0000000J) is transferred to the comparison data holding means 23 via the signal line 122.
Then, the comparison mask data of the binary number rlloOJ is stored in the comparison mask data holding means 24 via the signal line 123.

Processor l then transmits the conveyor ant swamp request to decoding means 20 via signal line 120. At this time, the signal line 42 is
If the access prohibition instruction has been sent to the access prohibition means 21 via 0, the decoding means 20 will not accept the compare and swap request and the access by the processor 1 will be awaited. On the other hand, if the access prohibition instruction from another shared memory access control section 4 is not sent to the access prohibition means 21, the decoding means 20 sends an access prohibition instruction to the other shared memory access control section 4 via the signal line 240. Send.

After sending this access prohibition instruction, the decoding means 20 next sends a read instruction to the shared storage device 5 via the signal '41A250, and at the same time, the decoding means 20 sends a read instruction to the shared storage device 5 via the signal '41A250.
The read address is sent to the main memory device 5 via.

The contents of the counting type semaphore 90, which is read data from the shared storage device 5 for this, are stored in the read data holding means 22 via the signal line 520.

The comparison means 25 stores the value r in the comparison mask data holding means 24.
Only the bytes corresponding to the bits of lJ are compared, and if they match, a value "1" is sent to the signal line 251. Now, the upper two bytes of the comparison data are r 0000 J, and if the semaphore count value 901 is r 0000 J (that is, state B where no process is using it), a match is detected.

The decoding means 20 transmits the signal line 2 to the shared storage device 5 at the timing when the output of the comparison means 25 is determined.
1, the write address is sent through the signal line 252, and the write data is sent through the signal line 253 to the address holding means 27.1. The data is sent from the write data holding means 26.

The write instruction on the signal line 201 is ANDed with the comparison result of the comparison means 25 on the signal line 251 in the AND circuit 28, and the AND signal is sent to the signal line 281. Therefore, only when the output of the comparing means 25 is rlJ, the counting type semaphore 90 of the coexisting storage device 5 is rewritten.

By operating in this way, the bytes corresponding to the value "0" in the comparison mask data holding means 24 are not compared, so the lower two bytes of the comparison data holding means 23 are ignored, and the last semaphore using process identification name is Regardless of 902, a compare and swap method can be used.

[Effects of the Invention] As explained above, according to the present invention, it is possible to mask any field of data to be compared in the compare and swap method, so even if there is a field for which comparison data cannot be created, the compare and swap method is not performed. A swap method can be used, and the scope of application of the compare and swap method can be expanded.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a block diagram of an embodiment of the shared memory access control unit 2, FIG. 2 is a block diagram showing an example of a multiprocessor system to which the present invention is applied, and FIG. 3 is a counting type It is an explanatory diagram of a semaphore. In the figure, 1 and 3 are processors, 2 and 4 are shared memory access control units, 5 is a shared storage device, 20 is a decoding means, 21 is an access prohibiting means, 22 is a successive data holding means, and 23 is a comparison data holding means , 24 is comparison mask data holding means, 25 is comparison means, 26 is write data holding means, 27 is address holding means, and 28 is an AND circuit.

Claims (1)

[Scope of Claims] When accessing a shared resource on a shared storage device shared with other processors, data stored in a predetermined area on the shared storage device and comparison data prepared by the own processor are used. A comparison and comparison method in a multiprocessor system configured to access the shared resource by rewriting data stored in the predetermined area with predetermined data of its own processor only when a predetermined comparison result is obtained. In the swap method, a comparison mask data holding means for storing comparison mask data indicating a field to be compared between data stored in the predetermined area and comparison data prepared by the own processor; and comparison means for comparing the comparison data prepared by the own processor with the comparison data prepared by the own processor according to the contents of the comparison mask data held in the comparison mask data holding means, and according to the comparison result of the comparison means, A compare-and-swap method in a multiprocessor system characterized by controlling whether or not to execute rewriting processing of data stored in an area.