JPH11134202A - Task switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To preserve a task state at the time of switching a task and to suppress the use quantity of a context preservation part to a minimum since a large quantity of necessary context information is preserved in a whole task state because the task state at the time of calling the task cannot be discriminated in a former task switching device and the use quantity of the context preservation part is preserved since unnecessary context information is preserved in the task state. SOLUTION: Since the task state at the time of calling task switching is preserved, a task state identification part 23 preserves identification information 32 in the task state into the specified area of the context preservation part 31. A restoration state identification part 26 can identify the task state before task switching from identification information 32 of the context preservation part 31 after a task switching processing. Thus, context information 33 of the context preservation part 31 is optimized and the use quantity of the context preservation part 31 can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a task switching device incorporated in a microprocessor or the like.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional task switching device.

In FIG. 1, a task switching device 111
Comprises a context saving unit 123, a task switching unit 124, and a context return unit 125, and reads and writes data from and to the context storage unit 131. Also,
The task section 121 stores a normal program, and the task independent section 122 stores an interrupt program. The program is a machine language, and includes a program converted from an assembler (programs 1 and 3) and a program converted from a high-level language such as C language (programs 2 and 4).

The task switching device 111 includes a task unit 12
When one or the task independent unit 122 attempts to execute a task different from the task (program) currently being executed,
After performing the task switching process, an arbitrary task is executed. Therefore, when the task of the task independent unit 122 is interrupted and executed while the task of the task unit 121 is executing (interrupt), the task of the task independent unit 122 is further interrupted and executed while the task of the task independent unit 122 is executing. (Multiple interrupts). After execution of the interrupt is completed, execution of the original task is resumed.

The operation of the conventional task switching device 111 having the above configuration for saving and restoring the context information 141 necessary for causing the context storage unit 131 to execute the task unit 121 and the task independent unit 122 will be described. (1) Operation of Saving Context Information 141 to Context Saving Unit 131 When the task unit 121 or the task independent unit 122 attempts to execute a task different from the task currently being executed, the task switching device 111 operates regardless of the task state. All the fixed amount of context information 141 is stored in the context storage unit 131.
To save. Note that the context information 141 refers to all information for executing the original task.
(Program status word) and the like. (2) Operation for Returning Context Information 141 from Context Storage Unit 131 The context recovery unit 125
1 is restored, and the execution of the original task is resumed.

[0006]

However, the above-described conventional task switching device 111 stores all the fixed amount of context information 141 in the context storage unit 131 regardless of the type of the currently executed task. Was. For this reason, there is a problem that the processing time for saving and restoring increases, and that a large capacity of the context saving unit 131 is required.

[0007] That is, although the amount of information to be stored is different between a case where a program converted from an assembler and a case where a program is converted from a C language are executed before the task is switched. And always stored certain information.

More specifically, the compiler for converting the C language defines the number of registers to be used, and does not use all the registers of the hardware. The assembler, on the other hand, allows the author to use registers freely.

Therefore, if an interrupt occurs during execution of a task using a machine language converted from the C language, it is sufficient to save only the number of registers specified by the compiler.
If an interrupt occurs during execution of a task in the machine language converted from the assembler, it is necessary to save the information of all registers provided in the hardware.

In view of the foregoing, it is an object of the present invention to minimize the processing time for saving and restoring a context and the amount of use of a context storage unit by optimizing the amount of context information saved at the time of task switching. I do.

[0011]

In order to solve this problem, a task switching device according to a first aspect of the present invention identifies a context that needs to be saved, and saves identification information to a predetermined area. A context saving unit that saves the context identified by the task state identification unit; a return state identification unit that reads identification information from the predetermined area to identify a context that needs to be restored; And context return means for returning the identified context.

According to a second aspect of the present invention, there is provided the task switching apparatus according to the first aspect, wherein the task state identifying means determines whether the task switching is performed by an assembler language program or a high-level language program. Information is the identification information.

According to a third aspect of the present invention, there is provided the task switching apparatus according to the second aspect, wherein the context saving means is configured such that the task switching is performed by the high-level language program by the task state identification means. If it is identified, a context that does not include a register defined as a destructive register in the language processing system of the high-level language is saved.

According to a fourth aspect of the present invention, in the task switching apparatus according to the third aspect, the context saving means is arranged such that a register for storing an argument or a return value is the destruction register. Even if the register is included in the register defined as, the register is saved.

According to a fifth aspect of the present invention, there is provided the task switching device according to the third aspect, wherein the context saving means is configured such that the task switching by the task state identification means is performed by a high-level language program. Even if the task is identified, if the task switching is performed by a program independent of each task, the register defined as the destruction register is saved.

According to a sixth aspect of the present invention, in the task switching apparatus according to the fifth aspect, the program independent of each task is an interrupt program.

According to a seventh aspect of the present invention, there is provided the task switching apparatus according to the first aspect, wherein the identification information indicates which resource is included in the context to be saved or restored, for each bit. It is assumed that the allocated information or the state of the included resource is encoded information.

According to an eighth aspect of the present invention, in the task switching apparatus according to any one of the first to seventh aspects, a context is saved by the predetermined area and the context saving means. The region is defined as being continuous with each other in a predetermined context storage region.

A task switching device according to a ninth aspect of the present invention is the task switching device according to any one of the first to seventh aspects, wherein a context of the predetermined area is saved by the context saving means. At this time, the resources included in the context are part or all of the unused area generated when the resources are saved after being arranged in a predetermined data length.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is a diagram showing the configuration and use of a task switching device according to an embodiment of the present invention.

In FIG. 1, the task switching device 11
A task state identification unit 23, a context saving unit 24,
The context switching unit 3 includes a task switching unit 25, a return state identification unit 26, and a context return unit 27.
Data is read from and written to 1.

In this embodiment, the task state identification unit 2
3 identifies whether the currently executing task is a machine language converted from an assembler or a machine language converted from a high-level language such as C language, and information to be saved if the task is a machine language converted from C language or the like. The amount is optimized.

That is, if an interrupt occurs during execution of a task using the machine language converted from the assembler,
Save the information of all registers provided in hardware. On the other hand, if the language is a machine language converted from the C language or the like, information of only the register specified by the compiler is saved.

With respect to the task switching device 11 of the present invention having the above-described configuration, an operation of saving and restoring a context necessary for executing the task unit 21 and the task independent unit 22 in the context saving unit 31 will be described. (1) Task state saving operation of the task state identification unit 23 The task state identification unit 23 distinguishes whether the currently executing task is a machine language converted from an assembler or a machine language converted from a C language or the like. The information of the state is stored in the specified unused area of the context storage unit 31 with the identification information 3.
2, and the status is passed to the context saving unit 24.

Note that the above distinction is generally made so that the machine language converted from the assembler and the machine language converted from the C language are stored in different memory spaces, so that it is recognized which memory space is stored. It is realized by doing. (2) Context saving unit 3 of context saving unit 24
Save operation to 1 The context save unit 24 saves the optimal context information 33 corresponding to the task state in the task storage unit 31 based on the task state passed from the task state identification unit 23. (3) Return Operation of Context Information 33 of Return State Identification Unit 26 The return state identification unit 26 reads the identification information 34 stored in a specific area of the context storage unit 31, and reads the context stored in the context storage unit 31. Information 3
5 as well as information on the type of the saved context information 35.
Pass to 7.

Thus, since the amount of information to be stored is switched, necessary information can be restored. (4) Context storage unit 3 of context return unit 27
Return operation from 1 The context return unit 27 reads the context information 35 from the context storage unit 31 based on the information passed from the return state identification unit 26, restores the context information 33, and executes the next task. Let it.

The task switching device according to the present embodiment will be described below with reference to the flowchart and the state of the context storage unit.

First, FIG. 2 is a diagram showing registers that can be a context of a processor targeted by the task switching device of the present embodiment. This processor includes 24-bit data registers D0 to D3, address registers A0 to A3, a program counter PC, and a 16-bit processor status word PSW. (1) Task switching call from the task unit 21 The task unit 21 is mainly configured by a user application task, and performs task switching in units of functions.

With regard to the context saving, the task state identifying unit 23 and the context saving unit 24 operate as follows.

FIG. 3 is a program flowchart for saving context information, FIG. 4 is a diagram showing the structure of a context storage unit when the task switching device 11 is called in assembler language, and FIG. 5 is a diagram showing the task switching device 11 in high-level language. FIG. 6 is a diagram illustrating a structure of a context storage unit when called.

In the case of a task switching call in the assembler language (starting from step 201), a save area is secured in the context storage unit 31 (step 20).
3). The save area requires 38 bytes for storing all the contexts shown in FIG. Next, identification information indicating the assembler language is stored (step 204). The identification information is indicated as a value 0 in the LSB of the 1-byte area 402 obtained by adding 3 from the beginning of the context storage unit. Anything other than the LSB is acceptable, but from the viewpoint of ease of determination, it is set to 0 except for the LSB. Then, the context information required to be saved only for the call from the assembler language is saved (step 205). Here, the data register D0
, D1, and the contents of the address register A0 as the context 8 information to the context 10 information, respectively.
9 to 411. Finally, save the context information necessary for the assembler language and high-level language (Step 2
08). Here, the contents of the data registers D2 and D3, the address registers A1 to A3, the program counter PC, and the processor status word PSW are defined as context 1 information to context 7 information, respectively, in the areas 401 and 40.
It is saved to 3-408. Thus, the saving of the context information is completed. Context 2 information to context 6 information and context 8 information to context 10
The information is stored in the lower 3 bytes of each area as in the context 1 information.

In the case of a task switching call in a high-level language such as the C language (starting from step 202), a save area is secured in the context storage unit 31 (step 2).
06). The save area is a data register D0 defined as a destruction register from the context shown in FIG.
And only 26 bytes are required to store anything except D1 and address register A0. A destruction register is a register that is handled by a language processing system such as a compiler as a register that does not need to guarantee a value between functions of a program. Next, the identification information indicating the high-level language is stored (step 207). The identification information is indicated as the value 1 in the LSB of the 1-byte area 402 obtained by adding 3 from the top of the context storage unit. Anything other than the LSB is acceptable, but from the viewpoint of ease of determination, it is set to 0 except for the LSB. Then, necessary context information common to both the assembler language and the high-level language is saved (step 208). Here, the contents of the data registers D2 and D3, the address registers A1 to A3, the program counter PC, and the processor status word PSW are saved in the area 401 and the areas 403 to 408 as context 1 information to context 7 information, respectively. Thus, the saving of the context information is completed. The context 2 information to the context 6 information correspond to the context 1
Like the information, it is stored in the lower 3 bytes of each area.

Regarding the context restoration, the restoration state identification unit 26 and the context restoration unit 27 operate as follows.

FIG. 6 is a program flowchart for restoring context information. First, the return state identification unit 2
6 is an area 40 in which 3 is added to the head of the context storage unit
Then, identification information is read out from Step 2 (Step 301), and it is determined whether the call is from an assembler language or a high-level language (Step 302). If the 1-byte data of the area 402 is 0, the former is 1, and if it is 1, the latter is the latter.

If it is determined that the call is made from the assembler language, the context information saved only in the assembler language is restored (step 303), and the area is released (step 304). Specifically, in FIG.
9 to 411 to context 8 information to context 10
The information is taken out and stored in the data register D0 and the address registers A0 and A1, respectively. Subsequently, the common saved context information is restored to open the area (step 305). Specifically, the area 401 and the area 4
Context 1 information to Context 7 from 03 to 408
The information is taken out and the data registers D1 to D3,
Address registers A2 and A3, program counter P
C, stored in the processor status word PSW. Thus, the saving of the context information is completed. The release of the area is realized by updating the stack pointer or the like.

If it is determined that the call is made from a high-level language, the commonly saved context information is restored and the area is released (step 305). It is not necessary to return the data register D0 and the address registers A0 and A1 defined as the destruction registers. Specifically, the context 1 information to the context 7 information are extracted from the area 401 and the areas 403 to 408, and the data registers D1 to D3 and the address registers A2 and A3 are respectively obtained.
3. Program counter PC, processor status word PSW
To be stored. Thus, the saving of the context information is completed. The release of the area is realized by updating the stack pointer or the like. (2) Task switching call from the task independent unit 22 The task independent unit 22 is mainly an interrupt program. Therefore, it is necessary to save and restore all contexts even in the case of a task switching call in a high-level language. In both the assembler language and the high-level language, the structure of the context storage unit is the same as that shown in FIG. 4, and the saving and restoring operations are the same as in the case of the assembler language (1).

As described above, according to the embodiment of the present invention,
Information indicating whether the task switching is performed in the assembler language or in the high-level language is stored in the area 402 of the context storage unit 31, and is saved in the context storage unit 31 by omitting the saving of the destruction register in the case of the high-level language. The amount of context information to be used is optimized, and the processing time for saving and restoring the context and the usage of the context storage unit 31 can be reduced. Further, the area 402
Since the unused area generated when the 3-byte long register is word-aligned is allocated, the usage of the context storage unit 31 due to the storage of the identification information does not increase.

In the above embodiment, only the binary information indicating whether the task switching is performed in the assembler language or in the high-level language is stored in the area 402 of the context storage unit 31. The context information stored in the unit 31 may be identified. For example, each bit of the 8-bit area 402 may indicate whether the data registers D0 to D3 and the address registers A0 to A3 are saved,
Up to 256 types of information may be encoded into 8 bits.

In the above embodiment, an unused area generated when a 3-byte register is word-aligned is assigned to the area 402 for storing identification information.
Unused bits in the area where the processor status word PSW is saved may be used as the processor status word PSW, or a dedicated area may be allocated. Even in the latter case, it is effective if the amount of the dedicated area is smaller than the reduction amount of the context information stored in the context storage unit. Especially,
It is often effective when storing the contents of a 4-byte length register.

Further, in the above embodiment, the destruction registers are the data registers D0 and D1 and the address register A0.
However, the present invention is not limited to these. Further, when a register for storing an argument or a return value is allocated to the destruction register, these registers may be saved or restored even in a task switching call in a high-level language.

[0042]

As described above, the task switching device according to the first aspect of the present invention provides a task state identification unit that identifies a context that needs to be saved and saves identification information to a predetermined area. Means for saving the context identified by the means, means for reading the identification information from the predetermined area to identify the context which needs to be restored, and means for restoring the context identified by the means for identifying the restored state And a context return unit.

According to this configuration, only contexts that need to be saved and restored are identified, the amount of context information to be saved is optimized, and the amount of context can be reduced.

According to a second aspect of the present invention, there is provided the task switching apparatus according to the first aspect, wherein the task state identifying means determines whether the task switching is performed by an assembler language program or a high-level language program. Information is the identification information.

According to this configuration, it is possible to efficiently identify a context that needs to be saved and restored using only the minimum identification information.

According to a third aspect of the present invention, in the task switching apparatus according to the second aspect, the context saving unit is configured such that the task switching by the task state identification unit is performed by a high-level language program. If it is identified, a context that does not include a register defined as a destructive register in the language processing system of the high-level language is saved.

According to this configuration, there is no need to save and restore the destruction register, the amount of context information to be saved is optimized, and the amount of context can be reduced.

According to a fourth aspect of the present invention, there is provided the task switching device according to the third aspect, wherein the context saving means is configured such that a register for storing an argument or a return value is the destruction register. Even if the register is included in the register defined as, the register is saved.

According to this configuration, the destruction register storing the argument or the return value is saved, and the context is easily switched without contradiction.

According to a fifth aspect of the present invention, there is provided the task switching device according to the third aspect, wherein the context saving unit is configured such that the task switching is performed by the high-level language program by the task state identification unit. Even if the task is identified, if the task switching is performed by a program independent of each task, the register defined as the destruction register is saved.

According to this configuration, in a program independent of each task, the destruction register is saved, and the context is easily switched without contradiction.

A task switching device according to a sixth aspect of the present invention is the task switching device according to the fifth aspect, wherein the program independent of each task is an interrupt program.

According to this configuration, the destruction register is saved in the interrupt program, and the context is easily switched without contradiction.

According to a seventh aspect of the present invention, there is provided the task switching device according to the first aspect, wherein the identification information indicates, for each bit, what resource is included in the context to be saved or restored. It is assumed that the allocated information or the state of the included resource is encoded information.

According to this configuration, it is possible to efficiently identify a context that really needs to be saved and restored only by referring to the identification information.

According to an eighth aspect of the present invention, in the task switching device according to any one of the first to seventh aspects, a context is saved by the predetermined area and the context saving means. The region is defined as being continuous with each other in a predetermined context storage region.

According to this configuration, the correspondence between the identification information and the context identified by the connection of the areas becomes clear.

A task switching device according to a ninth aspect of the present invention is the task switching device according to any one of the first to seventh aspects, wherein a context of the predetermined area is saved by the context saving means. At this time, the resources included in the context are part or all of the unused area generated when the resources are saved after being arranged in a predetermined data length.

According to this configuration, the amount of context does not increase due to the saving of the identification information.

[Brief description of the drawings]

FIG. 1 is a configuration and usage diagram of a task switching device according to an embodiment of the present invention.

FIG. 2 is a diagram showing registers that can be a context of a processor targeted by the task switching device of the embodiment;

FIG. 3 is a program flowchart for saving context information of the task switching device according to the embodiment;

FIG. 4 is a diagram showing a structure of a context storage unit when the task switching device 11 is called in an assembler language.

FIG. 5 is a diagram showing a structure of a context storage unit when the task switching device 11 is called in a high-level language.

FIG. 6 is a program flowchart for restoring context information of the task switching device according to the embodiment;

FIG. 7 is a diagram showing a configuration and a usage pattern of a conventional task switching device.

[Description of Signs] 11 Task switching device 21 Task section 22 Task independent section 23 Task state identification section 24 Context saving section 25 Task switching section 26 Return state identification section 27 Context restoration section 31 Context storage section 32, 34 Identification information 33, 35 Context information 111 Task switching device 121 Task part 122 Task independent part 123 Context saving part 124 Task switching part 125 Context return part 131 Context storage part 141 Context information

Claims (9)

[Claims] A task status identifying unit that identifies a context that requires saving and saves identification information to a predetermined area; a context saving unit that saves the context identified by the task state identifying unit; A task switching apparatus comprising: a return state identification unit that reads identification information from an area to identify a context that requires a return; and a context return unit that restores the context identified by the return state identification unit. 2. The task switching device according to claim 1, wherein the task status identification unit uses information as to whether the task switching is performed by an assembler language program or a high-level language program as the identification information. 3. The high-level language language processing system according to claim 3, wherein the context saving unit is configured to delete a register defined as a destruction register in the high-level language processing system when the task state identification unit identifies that the task switching is performed by a high-level language program. 3. The task switching device according to claim 2, wherein contexts not included are saved. 4. The context saving means saves a register for storing an argument or a return value, even if the register is included in a register defined as the destruction register. The task switching device according to claim 3, wherein: 5. The context saving unit according to claim 1, wherein the task switching is performed by a program independent of each task even when the task state identifying unit identifies that the task switching is performed by a high-level language program. 4. The task switching device according to claim 3, wherein when the error occurs, the register defined as the destruction register is saved. 6. The program independent of each task,
6. The task switching device according to claim 5, wherein the task switching device is an interrupt program. 7. The identification information according to claim 6, wherein the identification information is information on what kind of resources are included in the context to be saved or restored, or information on the allocation of the resources for each bit or information on the state of the included resources. 2. The task switching device according to claim 1. 8. The apparatus according to claim 1, wherein the predetermined area and an area in which the context is saved by the context saving unit are continuous with each other in a predetermined context saving area. The task switching device according to the paragraph. 9. The unused area generated when the context is saved by the context saving means and resources included in the context are aligned and saved to a predetermined data length when the context is saved by the context saving means. The task switching device according to any one of claims 1 to 7, wherein the task switching device is a part or a whole.