JP2937857B2 - Lock flag release method and method for common storage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and a method for releasing a lock flag of a common storage device, and more particularly to a method and a method for releasing a lock flag for controlling exclusive access to a common storage device.

[0002]

2. Description of the Related Art When a plurality of processors access a common storage device, as a method of resolving inconsistency caused by each processor accessing the same data, conventionally, a common storage device access right of a processor is managed in data units. Multiprocessor control systems are known.

In this multiprocessor control system, when a processor accesses a data area, a lock flag indicating that the data area is currently being accessed is set, so that a common area of another processor is included in the set. Eliminate access to.

Various means are employed for setting the lock flag and releasing the lock flag after accessing the common storage device for each information processing apparatus.

For example, Japanese Patent Application Laid-Open No. 61-259362 describes an exclusive control between processors when using a common storage device, but a plurality of computer systems such as a large general-purpose computer use a common storage device (extension). When a storage device is exclusively used, control using a similar lock flag is performed.

[0006]

When a failure occurs such that the lock flag release function does not operate properly in a processor in which a lock flag for exclusively accessing the common storage device is set, any of the other processors Cannot acquire the lock, so that the subsequent processor cannot execute.

[0007] A state in which the lock cannot be obtained by any other processor is generally called a deadlock state.

[0008] An object of the present invention is to eliminate deadlock when a failure occurs in which a lock flag cannot be released while a lock flag is set in a processor in which the lock flag is set, so that subsequent processes are not affected. And a lock flag release method and method for a common storage device.

[0009]

A lock flag release method for a common storage device according to the present invention has a lock flag for exclusively accessing a common storage device that can be commonly accessed by a plurality of processors for each processor. In the computer system, lock flag release impossible detection means for detecting that it is no longer possible to release the lock flag, lock flag release impossible notification means for notifying the detection result of the lock flag release impossible detection means, Lock flag reset means for releasing the lock flag in response to the output of the lock flag release impossible notification means.

Further, the lock flag release method for a common storage device according to the present invention is a computer system having a lock flag for exclusively accessing a common storage device that can be commonly accessed by a plurality of processors for each processor. Lock flag release impossible detecting means for detecting that the lock flag cannot be released, means for logically separating the common storage device from the processor, and And a lock flag resetting means for resetting the lock flag in accordance with the detection result of the separation detecting means.

The lock flag releasing method for a common storage device according to the present invention is a computer system having a lock flag for exclusively accessing a common storage device commonly accessible by a plurality of processors for each processor. The processor is configured to detect and notify the lock flag when it becomes impossible to release the lock flag, and to transmit a signal for notifying the lock flag. Is done.

Further, the lock flag releasing method for a common storage device according to the present invention is directed to a computer system having a lock flag for exclusively accessing a common storage device commonly accessible by a plurality of processors for each of the processors. When the processor detects that the lock flag cannot be released,
The common storage device is logically disconnected from the processor, and the lock flag is reset when detecting that the common storage device is logically disconnected from the processor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention. In the figure, a lock flag release method for a common storage device according to the present invention employs a lock flag 22 for exclusively accessing a common storage device 20 that can be commonly accessed by a plurality of processors 1 to n for each processor.
In the computer system having: a lock flag release impossible detecting means 1a for detecting that the lock flag 22 cannot be released; and a lock flag release for notifying the detection result of the lock flag release impossible detecting means 1a. The lock flag 22 is determined by the output of the lock flag release impossible notification unit 1b and the lock flag release disable notification unit 1b.
And a lock flag reset unit 21 for releasing the lock flag.

Here, the common storage device 20 is connected to n processors 1 to n, and each of the processors 1 to n includes lock flag release disable detection means 1a to na and lock flag release disable notification means 1b to nb. I have.

By the way, when the processors 1 to n access the common storage device 20, each processor sets the lock flag 22 before starting the access, and resets the lock flag 22 after the access is completed. While one processor is being set, another processor cannot be set.
Such a normal set / reset method is known, and is described, for example, in Japanese Patent Application Laid-Open No. 61-259362.

According to the present invention, before the lock flag 22 is reset in a normal manner, a fault occurs in the processor 1,
Further, it shows a countermeasure in a case where the content of the failure makes resetting of the lock flag impossible.

For example, in an information processing system such as a large general-purpose machine, the setting / resetting of the lock flag as described above is controlled by executing a lock command. In such a system as described above, a redundant code such as a parity bit is often added to an interface between devices in order to enhance reliability, but a failure occurs in an interface or a register involved in transmission / reception of a lock command. However, when a parity error is fixedly detected, the lock flag cannot be reset.

Lock flag release impossible detecting means 1 of the present invention
“a” is a means for detecting the above-described failure. The output of the lock flag release impossible detection means 1a is reported to the lock flag release disable notification means 1b via a signal line, and the lock flag release disable notification means 1b sends the lock flag 22 release to the common storage device 20. Notify that is no longer possible.

The common storage device 20 receives the above notification, and the lock flag reset means 21
Reset.

In the case of other processors, the lock flag 22 is reset in exactly the same manner as described above.

Further, a lock flag and a lock flag reset means may be provided for each of the plurality of processors.

FIG. 2 is an explanatory view showing a second embodiment of the present invention. In the figure, a lock flag release method for a common storage device according to the present invention is implemented by a
In a computer system having a lock flag 33 for exclusively accessing the common storage device 30 that can be commonly accessed from n for each processor, it is detected that the lock flag 33 cannot be released. Lock flag release impossible detecting means 11a, means 11b for logically separating the common storage device 30 from the processor, and logical separation detecting means for detecting that the common storage device 30 is logically disconnected from the processor 31 and a lock flag resetting means 32 for resetting the lock flag 33 in accordance with the detection result of the separation detecting means 31.

Here, the common storage device 30 is connected to n processors 11 to 1n, and each of the processors 11 to 1n includes lock flag release impossible detecting means 11a to 1na and logical separating means 11b to 1nb.

The setting / resetting of the lock flag 33 in the normal state operates in the same manner as in the first embodiment shown in FIG. 1, and the same applies to the failure in which the lock flag cannot be released.

In a computer system using a common storage device, for example, a large general-purpose computer system, an OS or application software manages whether or not each processor can access the common storage device.

Here, assuming that the above management is performed by the OS, the OS has a table for managing whether or not the common storage device is allocated for each processor under the OS.

When allocating (logically incorporating) the common storage device to an arbitrary processor, the OS registers that fact in the management table. Also, when an arbitrary processor deallocates (logically separates) the common storage device, the OS registers the fact in the management table.

The above operation is performed as follows. For example, when the processor allocates a common storage device by issuing an instruction for controlling the configuration (hereinafter, referred to as a configuration control instruction) from the OS, the processor operates as follows. Is deallocated by providing an FF (Flip Flop) or the like that becomes “0”. Here, the above FF is referred to as a Config flag.

Referring again to FIG. 2, the logical disconnecting means 11b is means for setting the above-mentioned Config flag to "0" when the common storage device 30 is deallocated from the processor 11.

According to the present invention, the above-mentioned logical separating means 11 is used.
b can be started not only by the configuration control command from the normal OS but also by the output of the lock flag release impossible detecting means 11a.

Then, the logical disconnection detecting means 31
When the state value of the Config flag is changed from “1” to “0”, the lock flag reset unit 32
Notify. The lock flag reset unit 32 resets the lock flag 33.

In the case of other processors, the lock flag 33 is reset in exactly the same manner as described above.

As in the first embodiment, logical disconnection detecting means, lock flag resetting means, and lock flag may be provided for each of the plurality of processors.

[0035]

As described in detail above, according to the present invention, when the lock flag of the common storage device becomes incapable of being released, it is detected and forcibly reset. Even if a failure that cannot be canceled occurs, it can be reset. Therefore, it is possible to avoid a deadlock state of the system and continue the subsequent process.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the present invention.

[Explanation of symbols]

 1-n processor 1a-na Lock flag release impossible detection means 1b-nb Lock flag release disable notification means 20 Common storage device 21 Lock flag reset means 22 Lock flag

Claims (2)

(57) [Claims] 1. A computer system having a lock flag for exclusively accessing a common storage device that can be commonly accessed by a plurality of processors for each of the processors , wherein each of the plurality of processors has the lock flag a lock flag releasing undetectable means for detecting that became impossible to release the said common storage device the detection result of the lock flag releasing undetectable means
And a lock flag releasing non notification means for notifying, the common storage device, the common memory device characterized by having a lock flag reset means for releasing the lock flag by the output of the lock flag releasing non notification means Lock flag release method. 2. A computer system having a lock flag for exclusively accessing a common storage device that can be commonly accessed by a plurality of processors for each processor , wherein each of the plurality of processors has a lock flag. a lock flag releasing undetectable means for detecting that became impossible to cancel, and means for disconnecting said common memory device logically from the processor
The common storage device has a disconnection detection unit that detects that the processor has been logically disconnected from the common storage device by the disconnection unit, and resets the lock flag according to a detection result of the disconnection detection unit. A lock flag reset method for the common storage device, comprising: a lock flag reset unit.