T-Kernel Specification (1.B0.02)

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194 CHAPTER 4. T-KERNEL/OS FUNCTIONS tk dis dsp Disable Dispatch [C Language Interface] ER ercd = tk_dis_dsp ( ) ; [Parameters] None [Return Parameters] ER ercd Error code [Error Codes] E OK E CTX Normal completion Context error (issued from task-independent portion) [Description] Disables task dispatching. Dispatch disabled state remains in effect until tk ena dsp is called enabling task dispatching. While dispatching is disabled, the invoking task does not change from RUN state to READY state or to WAIT state. External interrupts, however, are still enabled, so even in dispatch disabled state an interrupt handler can be started. In dispatch disabled state, the running task can be preempted by an interrupt handler, but not by another task. The specific operations during dispatch disabled state are as follows. • Even if a system call issued from an interrupt handler or by the task that called tk dis dsp results in a task going to READY state with a higher priority than the task that called tk dis dsp, that task will not be dispatched. Dispatching of the higher-priority task is delayed until dispatch disabled state ends. • If the task that called tk dis dsp issues a system call that may cause the invoking task to be put in WAIT state (e.g., tk slp tsk or tk wai sem), error code E CTX is returned. • When system status is referenced by tk ref sys, TSS DDSP is returned in sysstat. If tk dis dsp is called for a task already in dispatch disabled state, that state continues with no error code returned. No matter how many times tk dis dsp is called, calling tk ena dsp just one time is enough to enable dispatching again. The operation when the pair of system calls tk dis dsp and tk ena dsp are nested must therefore be managed by the user as necessary. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
4.9. SYSTEM MANAGEMENT FUNCTIONS 195 [Additional Notes] A task in RUN state cannot go to DORMANT state or NON-EXISTENT state while dispatching is disabled. If tk ext tsk or tk exd tsk is called for a task in RUN state while interrupts or dispatching is disabled, error code E CTX is detected. Since, however, tk ext tsk and tk exd tsk are system calls that do not return to their original context, such errors are not passed in return parameters by these system calls. Use of dispatch disabled state for mutual exclusion control among tasks is possible only if the system does not have a multiprocessor configuration. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
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T-Kernel Specification T-Kernel 1.B
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Contents 1 T-Kernel Overview 1 1.1
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CONTENTS v tk set flg (Set Event Fl
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CONTENTS vii 5.2.2 Address Space Ch
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CONTENTS ix td cal que (Reference Q
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List of Figures 1.1 Position of T-K
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List of Tables 2.1 State Transition
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System Call Notation In the parts o
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Index of T-Kernel/OS System Calls T
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INDEX OF T-KERNEL/OS SYSTEM CALLS x
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Index of T-Kernel/SM Extended SVC L
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Index of T-Kernel/DS System Calls T
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Chapter 1 T-Kernel Overview 1.1 Pos
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1.2. SCALABILITY 3 • Middleware m
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Chapter 2 Concepts Underlying the T
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2.2. TASK STATES AND SCHEDULING RUL
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2.2. TASK STATES AND SCHEDULING RUL
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2.3. INTERRUPT HANDLING 11 preceden
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2.5. SYSTEM STATES 13 Transient sta
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2.7. MEMORY 15 which the upper and
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Chapter 3 Common T-Kernel Specifica
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3.2. SYSTEM CALLS 19 /* * Common co
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3.2. SYSTEM CALLS 21 Ordinarily a f
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3.3. HIGH-LEVEL LANGUAGE SUPPORT RO
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Chapter 4 T-Kernel/OS Functions Thi
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4.1. TASK MANAGEMENT FUNCTIONS 27 t
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4.2. TASK-DEPENDENT SYNCHRONIZATION
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4.3. TASK EXCEPTION HANDLING FUNCTI
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4.4. SYNCHRONIZATION AND COMMUNICAT
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5.3. DEVICE MANAGEMENT FUNCTIONS 24
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5.3. DEVICE MANAGEMENT FUNCTIONS 24
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5.4. INTERRUPT MANAGEMENT FUNCTIONS
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5.5. IO PORT ACCESS SUPPORT FUNCTIO
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5.7. SYSTEM CONFIGURATION INFORMATI
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5.7. SYSTEM CONFIGURATION INFORMATI
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5.8. SUBSYSTEM AND DEVICE DRIVER ST
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260 CHAPTER 6. T-KERNEL/DS FUNCTION
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284 CHAPTER 7. REFERENCE INT tevptn
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286 CHAPTER 7. REFERENCE ER ercd =
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288 CHAPTER 7. REFERENCE INT ct = t
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290 CHAPTER 7. REFERENCE E OACV ERC
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T-Kernel Specification (1.B0.02)

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