JPH0227435A - Process control system by semaphore - Google Patents

Abstract

PURPOSE:To await that all events occur and to control a process when respective different semaphores correspond to plural events by providing a waiting cur order pointer corresponding to respective semaphores of a system at a PCB. CONSTITUTION:As an instruction for a process control system during the waiting at respective semaphores by a waiting cue order pointer 6, at least one semaphore number or above are made into an argument concerning a P instruction, and when all semaphores are wholly not closed, a V instruction is returned to an issued process, and when at least one or above are closed, a process control block PCB1 is connected to all waiting cues of the closed semaphore and the process is during the waiting. Even concerning the V instruction, only one semaphore number is made into the argument, when the process is not during the waiting by other semaphore, the process corresponding to the PCB 1 is made into an execution waiting condition, and when the process is during the waiting at other semaphore, the function to return to the process to issue the V instruction is held. Thus, it can be waited that all events occur.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a process control method using semaphores, and in particular to a process control method in an operating system of an information processing device, and particularly relates to a process control method using semaphores, and particularly to a process control method in an operating system of an information processing device. This invention relates to synchronization between processes that can wait for each other and an exclusive control method for shared resources.

[Conventional technology]

Traditionally, instructions for this type of semaphore are generally Pfir.
The P command has a semaphore number as an argument, subtracts 1 from the value of this semaphore counter, and if this value is non-negative, it continues the currently executing process, and if it is negative, it continues the current process. This is an instruction that closes the running process and starts other processes waiting to be executed. On the other hand, the V instruction also has a semaphore number as an argument, adds 1 to this semaphore counter, and if this value is positive, it continues the currently executing process, and if it is less than 0, it waits at this semaphore counter. This is an instruction that puts one of the processes in a waiting state for execution. When the initial value of the semaphore counter is 0, it is used for synchronization between processes, and when it is positive, it is used for exclusive control of shared resources.

[Problem to be solved by the invention] The conventional process control method using semaphores described above is
The command can only specify a single semaphore number as an argument, and since multiple events are associated with different semaphore numbers, it has the disadvantage that it is not possible to wait for all of the events to occur. .

[Means to solve the problem]

The process system (push type) using semaphores according to the present invention is an operating system in which each process executed in an information processing device is managed by a corresponding gross cell control block on the main memory. Regarding the P instruction as an instruction for a process control method that has a waiting queue next pointer corresponding to each semaphore used in the process, the waiting queue next pointer expresses the waiting queue of the process waiting in each semaphore. takes at least one semaphore number as an argument, and if all semaphores specified by the argument are not blocked, returns to the process that issued the above ■ command, and if at least one of the semaphores is blocked, the above The process control block of the process that issued the P command is connected to all the waiting queues of the blocked semaphores, and the process is put on standby. If the semaphore is not in the blockage state, the process returns to the process that issued the above-mentioned (①) instruction, and if the semaphore is in the blockage state, one process control block is selected from the standby queue of the semaphore specified by the argument, and at the same time the process Check the waiting queue of other semaphores to which the control block is connected, and if it is not waiting on the pond semaphore,
Put the process corresponding to the process control block in the execution waiting state, and if it is waiting in another semaphore, the corresponding ■
It has the function of returning to the process that issued the instruction.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows the structure of a management table in one embodiment of the present invention, and FIG. 1(a) shows a process control block. In FIG. 1(a), a process control block (hereinafter referred to as PCB) main body 1 has a process name 2. Control information storage area 3. Execution status display section 4. Consists of a pending queue next pointer 5 and a waiting queue next pointer 6,
The standby queue next pointer 6 constitutes a standby queue next pointer string consisting of the number of semaphores used by the system.

FIG. 1(b) shows an execution queue.

In FIG. 1(b), the execution waiting top PCB pointer 7
is the execution queue next pointer 1 of the execution waiting top PCB8
0, and this pending queue next pointer 10 points to the next pending queue pointer 11 of the next pending PCB 9. This queue can be chained as long as the system allows.

The pending queue next pointer of the last PCB in the queue is -
1 is written.

FIG. 1(c) shows a waiting queue. The standby head pointer/semaphore counter column 12 is a standby queue head pointer 13.15.17.19 corresponding to the semaphore number.
．． ... and semaphore counters 14, 16, 18, 20.
It is composed of...

Note that the standby queue head PCB pointer 13.15°17.
19. ... is initialized to -1, and the semaphore counter 1
4.16, 18, 20. ... is a non-negative integer and is initially set to 1. The waiting queue is configured as follows. For example, if the standby queue head PCB pointer for an arbitrary semaphore number α is 15, and two processes PCB 21 and 24 are waiting at the semaphore, the standby queue head PCB pointer 15 is the semaphore number α of PCB 21.
, and the next waiting queue pointer 22 points to the next waiting queue pointer 25 corresponding to the semaphore number α of the PCB 24. O is written to the waiting queue next pointer 25 to indicate the end of the waiting queue. This queue can be chained as long as the system allows.

FIG. 1(C) shows that when the standby queue head PCB pointers of semaphore numbers β and γ are 17.19 in addition to the semaphore number α mentioned above, the process of PCB 21 first receives semaphore numbers α and β as arguments. Then, the process of PCB24 enters the waiting state by issuing the P command, and then the process of PCB24 enters the waiting state with the semaphore numbers α and γ as all arguments, and the last P command is issued.
The process of CB27 issues a P command with the semaphore number γ as an argument, and is in a waiting state.

Next, FIGS. 2(a) and 2(b) are flowcharts when the P command and the ■ command are executed for the semaphore, respectively. FIG. 3 is a flowchart of a process scheduler that controls process execution.

First, explanation will be given with reference to FIG. 2(a). The P command can specify at least one semaphore number as an argument,
When a process issues a P command, it first reads the PCB pointer at the head of the waiting queue and the semaphore counter (16
, 18, 20, etc.) (Sl). As a result, if all the values are 0 or more, control is returned to the original process that issued the P command (S3). If there is a negative semaphore counter, the control information of the process that issued the P command is placed on standby in the control information storage area 3 of the PCB of the process (34), and the execution status display 4 is set to "Waiting".
(S5).

Then, the queue is connected to the end of the standby queue whose semaphore number has a negative semaphore counter (S6). At this time, all standby queue next pointers of the PCB are set to 0. After that, the PCB is removed from the execution queue (S7
). Then, control is passed to the process scheduler (S8
).

Next, a description will be given with reference to FIG. 2(b). ■A command can specify a unique semaphore number as an argument, and a certain process can
When the command is issued, first, 1 is added to the semaphore counter of the semaphore number specified by the argument in the standby queue head pointer/semaphore counter column 12 (S9). If this value is 1 or more, control is returned to the process that issued the P command (SLL), and if it is less than 0, the PCB specified by the standby queue head PCB pointer of the semaphore number specified by the above argument is returned. Remove from standby (S12)
. At this time, the standby queue next pointer of the PCB is initialized to -1. Next, search for a pointer other than the initial value (-1) among all the waiting queue next pointers of the 20 colors, and if it exists, it means that it is waiting with another semaphore number, so the process that issued the V instruction can use it. Return control (313, 51
1). If it does not exist, it means that it is not waiting with another semaphore number, so connect the PCB to the execution queue (S14
), and sets the PCB execution status display to "wait for execution" (S15), and then passes control to the process scheduler (S16). As an example, in FIG. 1(c), if the ■ command is issued with the semaphore number γ mentioned above as an argument, and if the initial value of the semaphore counter 20 is 0, then in this state it is -2 and 1 is Since it is less than 0 even if added, the PCB is
Follow 24. PCB24 is removed from the waiting queue,
The waiting queue next pointer 26 is initialized to -1, and the waiting queue head PCB pointer 19 points to the waiting queue next pointer 28 of the PCB 27. However, PCB24
Since the waiting queue next pointer 25 is not the initial value, it is found that the process is waiting at another semaphore number (α), and control is returned to the original process. The process on the PCB 24 will be connected to the execution queue two more times when the V command is issued to semaphore number α.Next, this will be explained with reference to the flowchart of the process scheduler shown in FIG. When control is passed from the P or V instruction, the address of the PCB is first obtained from the execution waiting first PCB pointer 9 (S17). "Running" is set to "Running" (S19), variables necessary for the execution of the process are restored from the control information storage area 3 of the PCB (520), and the process is started (S21). If the process is not "waiting to be executed", the execution queue is followed and the execution status display section 4 of the PCB is sequentially inspected to find the process that is "waiting to be executed" and activated (S22, 323).If all the processes are not "waiting to be executed" If so, wait for a hardware interrupt (S24>).

〔Effect of the invention〕

As explained above, the present invention provides a standby queue next pointer corresponding to each semaphore of the system on the PCB, so that when a plurality of events are made to correspond to different semaphores, all the events can be prevented from occurring. This has the effect of controlling the waiting process.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of a management table in an embodiment of the present invention.
) is a diagram showing the execution queue, Figure 1 (c) is a diagram showing the waiting queue, Figure 2 (a) is a diagram showing the processing flow of the P instruction, and Figure 2 (b) is the diagram showing the processing of the ■ instruction. Diagram showing the flow of
The figure shows the flow of the process scheduler. 1.8, 9, 21, 24.27...PCB, 2...
Process name, 3... Control information storage area, 4.1. Execution status display section, 5, 10.11...Execution queue next pointer, 6, 22, 23, 25, 26.28...Waiting queue next pointer, 7...Execution queue head PCB pointer, 12 ...Waiting queue head PCB pointer/semaphore counter sequence, 13, 15, 17.19...Waiting queue head PCB pointer, 14, 16゜a (b)

Claims (1)

[Claims] In the operating system of the information processing device, in which each process executed in the information processing device is controlled by a management table on the main memory called a process control block corresponding to each process, each process control block includes a control table that is used in the operating system. Regarding the P instruction as an instruction for a process control method that has a waiting queue next pointer corresponding to each semaphore, and expressing the waiting queue of the process waiting in each semaphore using the waiting queue next pointer,
If at least one semaphore number is specified as an argument and all semaphores specified by the argument are not blocked, the P
Returns to the process that issued the instruction, and when at least one of the semaphores is blocked, connects the process control block of the process that issued the P instruction to all waiting queues of the blocked semaphores, and makes the process standby. , for the V instruction, the only semaphore number is taken as an argument, and if the semaphore specified by the argument is not in a blocked state, the process returns to the process that issued the V instruction, and if the semaphore is in a blocked state, the process returns from the waiting queue of the semaphore. Selecting and deselecting one process control block, at the same time checking the waiting queues of other semaphores to which the process control block is connected, and placing the process corresponding to the process control block in a waiting state for execution if it is not waiting in another semaphore; A process control method using a semaphore, characterized in that it has a function of returning to the process that issued the V instruction if it is waiting in another semaphore.