JP2004005227A - Arithmetic processing system, exception handling method on computer system, and computer program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To appropriately handle an exception even under an insufficient stack. <P>SOLUTION: On or in an operating system, a special task for handling an exception is run, and a cue for requesting exception handling from the task is prepared. If an exception condition occurs in a general task, information necessary for exception handling is added to the cue and, at the same time, the task in the exception condition is brought to a halt. An insufficient stack can be handled as one exception condition and subjected to exception handling. Even if an exception occurs under a small remaining stack, exception handling is carried out regardless of stack insufficiency. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an arithmetic processing system, an exception processing method on a computer system, and a computer program for processing an exception state occurring in a program being executed, and particularly to performing exception processing while saving a state of a task. The present invention relates to an arithmetic processing system, an exception handling method on a computer system, and a computer program.
[0002]
More specifically, the present invention relates to an arithmetic processing system that performs exception processing even if an exception occurs when the remaining amount of the stack is small, an exception processing method on a computer system, and a computer program.
[0003]
[Prior art]
Along with recent breakthroughs in LSI (Large Scale Integration) technology, various types of information processing devices and information communication devices have been developed and marketed, and have penetrated deeply into everyday life. In this type of device, a CPU (Central Processing Unit) or other processor executes a predetermined program code in an execution environment provided by an operating system to provide various processing services. .
[0004]
By the way, a situation may occur in which the execution of a program cannot be continued without the prohibited operation or the help of the operating system. For example, a case where a division by zero is executed or an access to an area for which access is prohibited occurs. Such a state is generally called an "exception state" and requires exception handling.
[0005]
In an existing operating system, processing of an exceptional state is often performed by a method as shown in FIG.
[0006]
It is assumed that task A is being executed under the control of the operating system. In such a case, as shown, task A uses a part of the stack area allocated to itself, and the program counter (PC) points to the address currently being executed.
[0007]
Here, when an exceptional state occurs in task A, the state at the time of occurrence of the exceptional state is stored in the stack area of task A, and the process jumps to the exception handling routine. As a result, the state at the time of occurrence of the exception (including the exception occurrence address) uses the stack, and the address of the exception handling routine is written in the program counter.
[0008]
Thereafter, when the exception processing is completed, the state saved in the stack is restored. That is, the instruction jumps to the instruction in which the exception has occurred or the instruction following the instruction. The program counter indicates the address of the instruction in which the exception has occurred or the address of the next instruction.
[0009]
In other words, according to the conventional method, when an exception occurs, the state of the task (for example, the value of a general-purpose register or a program counter of the processor) is saved on the stack, the process jumps to an exception handling routine, and the exception processing is completed. Then, the system is returned to the state before the exception occurred by reading the value stored in the stack back to the original location.
[0010]
However, in this method, when trying to execute exception processing of a plurality of tasks in parallel, it is necessary to secure an exception state on the stack for each task. For this reason, there is a problem that it is not possible to process an exceptional state caused by a shortage of the stack. In other words, in a situation where the stack is insufficient, an area for saving the state cannot be secured, so that exception processing cannot be performed.
[0011]
Although this problem can be mitigated by dynamically expanding the stack, if this expansion fails, exception handling is still impossible.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to provide an excellent arithmetic processing system, an exception handling method on a computer system, and a computer program, which can appropriately handle an exception state occurring in a running program. .
[0013]
A further object of the present invention is to provide an excellent arithmetic processing system and an exception processing method on a computer system, which can save a state of a task such as a register value and a program counter value of a processor and can appropriately perform exception processing. , As well as computer programs.
[0014]
A further object of the present invention is to provide an excellent arithmetic processing system and a computer system capable of appropriately performing exception processing without fear of stack shortage even when an exception occurs in a situation where the remaining amount of the stack is small. An object of the present invention is to provide an exception handling method and a computer program.
[0015]
Means and Action for Solving the Problems
The present invention has been made in view of the above problems, and a first aspect thereof is an arithmetic processing system that executes a program,
An exception handling task that handles an exception condition that has occurred in the program;
An exception handling queue for requesting the exception handling task to process an exception state;
A control unit that writes information necessary for exception processing to the exception processing queue in response to the occurrence of an exception state during execution of a general task, and shifts the task in which the exception state has occurred to a stop state,
An arithmetic processing system comprising:
[0016]
However, the term “system” as used herein refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter in particular.
[0017]
A second aspect of the present invention is an exception handling method on a computer system,
In response to the occurrence of an exceptional state during execution of a general task, an exceptional processing request step for writing information necessary for exceptional processing to an exceptional processing queue and shifting the task in which the exceptional state has occurred to a suspended state,
An exception handling step of taking out an element from the exception handling queue and handling an exception handling request;
Exception handling method on a computer system characterized by comprising:
[0018]
A special task for handling exceptions, that is, an exception handling task is operating on or in the operating system, and an exception handling queue for requesting the exception handling task to perform exception handling is provided. When an exceptional state occurs in a general task, information necessary for exceptional processing is added to the exception handling queue, and at the same time, the task in which the exceptional state occurred transitions to a stopped state. Here, the stack area used for exception processing is an area allocated to the exception processing task, and is not allocated to the task in which the exception has occurred. Further, the stack area of the exception handling task can secure a sufficient memory amount in advance.
[0019]
Therefore, according to the arithmetic processing system according to the first aspect of the present invention or the exception handling method on the computer system according to the second aspect of the present invention, the lack of stack is treated as one of the exceptional states, Exception handling can be performed. Further, even when an exception occurs in a situation where the remaining amount of the stack is small, the exception processing can be performed without fear of the shortage of the stack.
[0020]
Here, the control unit may write an exception processing request in the exception processing queue according to the priority of the task in which the exception has occurred. If the priority of the exception handling task is lower than that of the exception occurrence task, the priority of the exception handling task may be set equal to the priority of the exception occurrence task, and rescheduling may be performed.
[0021]
In such a case, the execution of the exception handling task can be prevented from being disturbed by another task having a low priority.
[0022]
Further, the exception handling task can set the priority of the exception handling task equal to the priority of the request at the head of the queue so as not to disturb the execution of other tasks having a higher priority. .
[0023]
According to a third aspect of the present invention, there is provided a computer program described in a computer-readable format so as to execute, on a computer system, processing of an exceptional state occurring during task execution,
In response to the occurrence of an exceptional state during execution of a general task, an exceptional processing requesting step of writing information necessary for exceptional processing to an exceptional processing queue and shifting the task in which the exceptional state has occurred to a stopped state,
An exception processing step of removing an element from the exception processing queue and processing an exception processing request using a stack area allocated for exception processing;
A computer program characterized by comprising:
[0024]
A computer program according to a third aspect of the present invention defines a computer program described in a computer-readable format so as to realize a predetermined process on a computer system. In other words, by installing the computer program according to the third aspect of the present invention in a computer system, a cooperative action is exerted on the computer system, and the arithmetic processing according to the first aspect of the present invention is performed. The same operation and effect as those of the exception processing method on the system or the computer system according to the second aspect of the present invention can be obtained.
[0025]
Further objects, features, and advantages of the present invention will become apparent from more detailed descriptions based on embodiments of the present invention described below and the accompanying drawings.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0027]
FIG. 1 schematically shows a hardware configuration of an arithmetic processing system 10 provided for implementing the present invention. As shown in FIG. 1, the arithmetic processing system 10 includes a processor 11, a random access memory (RAM) 12, a read only memory (ROM) 13, a plurality of input / output devices 14-1, 14-2,. And a timer 15.
[0028]
The processor 11 is a main controller of the arithmetic processing system 10 and executes various program codes under the control of an operating system (OS).
[0029]
A unit in which the operating system manages and controls program execution is generally called a "task". The arithmetic processing system 10 according to the present embodiment allows a plurality of tasks to exist in a program. Therefore, there are more tasks than the number of processors 11 which are entities that actually perform calculations.
[0030]
The operating system is designed to execute the tasks in a pseudo-parallel manner by frequently switching the tasks processed by the processor 11. Each task is assigned a task ID that can be distinguished from other tasks. Each task performs a series of operations, that is, a transaction, on data using the data area on the stack.
[0031]
In this embodiment, in addition to a general task, the operating system prepares a special task called an “exception processing task” for processing an exception state. Here, the exceptional state means a state where an operation prohibited during the execution of the program, such as division by zero or occurrence of access to an area where access is prohibited, has been performed. However, the details of the processing method of the exception processing task will be described later.
[0032]
The processor 11 is interconnected with other devices (described later) by a bus 16. Each device on the system bus 16 is assigned a unique memory address or I / O address, and the processor 11 can access a predetermined device by designating these addresses. The system bus 16 is a common signal transmission path including an address bus, a data bus, and a control bus.
[0033]
The RAM 12 is a writable memory, and is used to load a program code to be executed in the processor 11 and temporarily store work data of an execution program. Examples of the program code include a basic input / output system (BIOS), a device driver for operating hardware of peripheral devices, an operating system, and an application.
[0034]
The ROM 13 is a nonvolatile memory for permanently storing predetermined codes and data, and stores, for example, a BIOS and a self-diagnosis program (Power On Self Test: POST) at startup.
[0035]
The input / output device 14 includes a display interface 14-1 for connecting a display 21, a user input device interface 14-2 for connecting a user input device such as a keyboard 22 and a mouse 23, a hard disk 24, An external storage device interface 14-3 for connecting an external storage device such as the media drive 25, and a network interface card (NIC) 14-4 for connecting to an external network are included.
[0036]
The display interface 14-1 is a dedicated interface controller for actually processing a drawing command issued by the processor 11. The drawing data processed by the display interface 14-1 is temporarily written in, for example, a frame buffer (not shown), and then output to the screen by the display 21.
[0037]
The HDD 24 is an external storage device in which a magnetic disk as a storage carrier is fixedly mounted (well-known), and is superior to other external storage devices in terms of storage capacity, data transfer speed, and the like. Normally, the HDD 24 stores the program codes of the operating system to be executed by the processor 11, application programs, device drivers, and the like in a nonvolatile manner. Placing a software program on the HDD 24 in an executable state is called "installing" the program in the system. For example, an operating system for realizing the present invention and an application program designed to have a plurality of tasks can be installed on the HDD 24.
[0038]
The media drive 25 is a device for loading a portable medium such as a CD (Compact Disc), an MO (Magneto-Optical Disc), a DVD (Digital Versatile Disc), and accessing a data recording surface thereof.
[0039]
The portable medium is mainly used for backing up software programs, data files, and the like as computer-readable data, and for transferring them between systems (that is, including sales, distribution, and distribution). For example, it is possible to physically distribute and distribute an operating system that implements the present invention and an application program designed to have a plurality of tasks among a plurality of devices using these portable media. it can.
[0040]
The network interface 14-1 can connect the system 10 to a local network such as a LAN (Local Area Network) or a wide area network such as the Internet according to a predetermined communication protocol such as Ethernet (registered trademark). .
[0041]
On a network, a plurality of host terminals (not shown) are connected in a transparent state, and a distributed computing environment is constructed. On the network, distribution of software programs, data contents, and the like can be performed. For example, an operating system for realizing the present invention or an application program designed to have a plurality of tasks can be downloaded via a network.
[0042]
An interrupt level is assigned to each of the input / output devices 14-1, 14-2,..., And a predetermined event occurs (for example, GUI processing such as keyboard input or mouse click, completion of data transfer on a hard disk, etc.). ), The processor 11 can be notified via the interrupt request signal line 19. The processor 11 executes a corresponding interrupt handler in response to such an interrupt request.
[0043]
The timer 15 is a device that generates a timer signal at a predetermined cycle. An interrupt level is also assigned to the timer 15, and a periodic interrupt is generated for the processor 11 via the interrupt request signal line 19.
[0044]
An example of the arithmetic processing system 10 as shown in FIG. 1 is a compatible machine or a successor of a personal computer "PC / AT (Personal Computer / Advanced Technology)" of IBM Corporation. Of course, a computer having another architecture can be applied as the arithmetic processing system 10 according to the present embodiment.
[0045]
As described above, in this embodiment, a special task called an “exception processing task” for processing an exceptional state is prepared in addition to a general task. When an exception state occurs during normal task execution, the operating system requests the exception processing task for exception processing. Specifically, one queue called an exception processing queue is prepared in the system, and information such as an exception occurrence status is written in this queue. The exception handling task monitors this queue, and performs the process when an exception handling request arrives.
[0046]
FIG. 2 is a flowchart illustrating a processing operation performed by the operating system when an exception occurs during execution of a general task.
[0047]
When an exception occurs during execution of a general task (step S1), the operating system first causes the task in which the exception has occurred to transition to a stopped state (step S2).
[0048]
Next, the processing request of the exceptional state is inserted into the exception processing queue prepared by the operating system at a position arranged in order of priority (step S3). The priority at the time of insertion into the exception handling queue follows the priority of the task that caused the exception.
[0049]
Next, it is determined whether the exception handling task has a higher priority than the task in which the exception has occurred (step S4). If the exception handling task has a lower priority than the exception generating task, the priority of the exception processing task is set equal to the priority of the exception generating task (step S5), and the exception processing is performed by another task having a lower priority. Ensure that task execution is not disturbed.
[0050]
Then, the task is rescheduled, and the entire processing routine ends (step S6).
[0051]
FIG. 3 shows, in the form of a flowchart, a processing operation for the exception handling task to perform exception handling in response to a request for exception handling.
[0052]
First, the process waits until a request for exceptional processing reaches the queue (step S11). When the request for exception processing arrives, the head element of the queue is extracted (step S12), and the extracted request is processed (step S13).
[0053]
If the queue is not yet empty, set the priority of the exception handling task equal to the priority of the request at the head of the queue so that it does not interfere with the execution of other higher priority tasks. (Step S15), the process returns to step S12, and the same processing as described above is repeatedly executed for the next element in the queue.
[0054]
When the queue becomes empty (step S14), the process returns to step S11 and waits until the next request arrives at the queue.
[0055]
As shown in FIGS. 2 and 3, the priority of the exception handling task is controlled so as to match the highest priority of the tasks waiting for exception processing. As a result, an exception that has occurred in a high-priority task is processed with higher priority.
[0056]
Here, the stack area used for the exception processing is an area allocated to the exception processing task, and is not allocated to the task in which the exception has occurred. Further, a sufficient memory amount can be allocated in advance to the stack area of the exception handling task. Therefore, even if the task in which the exception occurs lacks the stack area, exception processing can be performed.
[0057]
[Supplement]
The present invention has been described in detail with reference to the specific embodiments. However, it is obvious that those skilled in the art can modify or substitute the embodiment without departing from the scope of the present invention. That is, the present invention has been disclosed by way of example, and the contents described in this specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims described at the beginning should be considered.
[0058]
【The invention's effect】
As described in detail above, according to the present invention, an excellent arithmetic processing system, an exception processing method on a computer system, and a computer system capable of appropriately processing an exception state occurring in a running program. Program can be provided.
[0059]
Also, according to the present invention, an excellent arithmetic processing system and exception processing on a computer system, which can save a state of a task such as a register value or a program counter value of a processor and can appropriately perform exception processing. Methods and computer programs can be provided.
[0060]
According to the present invention, a situation where the stack is insufficient can be treated as one of the exceptional states, and exception processing can be performed. Therefore, even if an exception occurs in a situation where the remaining amount of the stack is small, it is possible to perform the exception processing without fear of running out of the stack.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a hardware configuration of an arithmetic processing system 10 provided for implementing the present invention.
FIG. 2 is a flowchart showing a processing operation by an operating system when an exception occurs during execution of a general task.
FIG. 3 is a flowchart illustrating a processing operation by an exception processing task that performs exception processing in response to a request for exception processing.
FIG. 4 is a diagram illustrating an example of processing of an exceptional state by an existing operating system.
[Explanation of symbols]
10 arithmetic processing system 11 processor 12 RAM
13 ROM
14 I / O device 15 Timer 16 System bus 19 Interrupt request line 21 Display 22 Keyboard 23 Mouse 24 HDD
25 ... Media drive

Claims (11)

An arithmetic processing system that executes a program,
An exception handling task that handles an exception condition that has occurred in the program;
An exception handling queue for requesting the exception handling task to process an exception state;
A control unit that writes information necessary for exception processing to the exception processing queue in response to the occurrence of an exception state during execution of a general task, and shifts the task in which the exception state has occurred to a stop state,
An arithmetic processing system comprising: A stack area used for exception handling is assigned to the exception handling task,
The arithmetic processing system according to claim 1, wherein: The control unit writes an exception handling request in the exception handling queue according to the priority of the task that caused the exception,
The arithmetic processing system according to claim 1, wherein: When the exception handling task has a lower priority than the exception occurrence task, the control unit sets the priority of the exception handling task equal to the priority of the exception occurrence task, and reschedules.
The arithmetic processing system according to claim 1, wherein: The exception handling task sets the priority of the exception handling task equal to the priority of the request at the head of the exception handling queue,
The arithmetic processing system according to claim 1, wherein: An exception handling method on a computer system, comprising:
In response to the occurrence of an exceptional state during execution of a general task, an exceptional processing request step for writing information necessary for exceptional processing to an exceptional processing queue and shifting the task in which the exceptional state has occurred to a suspended state,
An exception handling step of taking out an element from the exception handling queue and handling an exception handling request;
An exception handling method on a computer system, comprising: In the exception handling step, an exception state is handled using a stack area allocated for exception handling.
7. The exception handling method on a computer system according to claim 6, wherein: In the exception handling request step, write an exception handling request to the exception handling queue according to the priority of the task that caused the exception,
7. The exception handling method on a computer system according to claim 6, wherein: In the exception handling requesting step, when the exception handling task has a lower priority than the exception occurrence task, the priority of the exception handling task is set equal to the priority of the exception occurrence task, and rescheduling is performed.
7. The exception handling method on a computer system according to claim 6, wherein: In the exception handling step, the priority of the exception handling task is set equal to the priority of the request at the head of the exception handling queue,
7. The exception handling method on a computer system according to claim 6, wherein: A computer program described in a computer-readable form so as to execute processing of an exceptional state occurring during task execution on a computer system,
In response to the occurrence of an exceptional state during execution of a general task, an exceptional processing request step for writing information necessary for exceptional processing to an exceptional processing queue and shifting the task in which the exceptional state has occurred to a suspended state,
An exception processing step of removing an element from the exception processing queue and processing an exception processing request using a stack area allocated for exception processing;
A computer program comprising:

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