T-Kernel Specification (1.B0.02)

More documents

Recommendations

Info

116 CHAPTER 4. T-KERNEL/OS FUNCTIONS 4.5.2 Message Buffer A message buffer is an object for achieving synchronization and communication by the passing of variable-size messages. Functions are provided for creating and deleting a message buffer, sending and receiving messages using a message buffer, and referencing message buffer status. A message buffer is an object identified by an ID number called a message buffer ID. A message buffer keeps a queue of messages waiting to be sent (send queue) and a queue of tasks waiting for message receipt (receive queue). It also has a message buffer space for holding sent messages. The message sender (the side making event notification) copies to the message buffer a message it wants to send. If there is insufficient space in the message buffer area, the message is queued for sending until enough space is available. A task waiting to send a message to the message buffer is put in the send queue. On the message receipt side (waiting for event notification), one message is fetched from the message buffer. If the message buffer has no messages, the task enters WAIT state until the next message is sent. A task waiting for receipt from a message buffer is put in the receive queue of that message buffer. A synchronous message function can be realized by setting the message buffer space size to 0. In that case both the sending task and receiving task wait for a system call to be invoked by each other, and the message is passed when both sides issue system calls. [Additional Notes] The message buffer functioning when the size of the message buffer space is set to 0 is explained here using the example in Figure 4.3. In this example Task A and Task B run asynchronously. • If Task A calls tk snd mbf first, it goes to WAIT state until Task B calls tk rcv mbf. In this case Task A is put in the message buffer send queue (a). • If Task B calls tk rcv mbf first, on the other hand, Task B goes to WAIT state until Task A calls tk snd mbf. Task B is put in the message buffer receive queue (b). • At the point where both Task A has called tk snd mbf and Task B has called tk rcv mbf, a message is passed from Task A to Task B; then both tasks go from WAIT state to a run state. Task A Task B Task A Task B tk snd mbf tk rcv mbf Send waiting state Receive waiting state ✲ tk rcv mbf tk snd mbf ✲ (a) tk snd mbf called first (b) tk rcv mbf called first Figure 4.3: Synchronous Communication by Message Buffer Tasks waiting to send to a message buffer send messages in their queued order. Suppose Task A wanting to send a 40-byte message to a message buffer, and Task B wanting to send a 10-byte message, are queued in that order. If another task receives a message opening 20 bytes of space in the message buffer, Task B is still required to wait until Task A sends its message. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
4.5. EXTENDED SYNCHRONIZATION AND COMMUNICATION FUNCTIONS 117 A message buffer is used to pass variable-size messages by copying them. It is the copying of messages that makes this function different from the mailbox function. It is assumed that the message buffer will be implemented as a ring buffer. Copyright c○ 2002, 2003 by T-Engine Forum T-Kernel 1.B0.02
Page 1 and 2:
T-Kernel Specification T-Kernel 1.B
Page 3 and 4:
Contents 1 T-Kernel Overview 1 1.1
Page 5 and 6:
CONTENTS v tk set flg (Set Event Fl
Page 7 and 8:
CONTENTS vii 5.2.2 Address Space Ch
Page 9 and 10:
CONTENTS ix td cal que (Reference Q
Page 11 and 12:
List of Figures 1.1 Position of T-K
Page 13 and 14:
List of Tables 2.1 State Transition
Page 15 and 16:
System Call Notation In the parts o
Page 17 and 18:
Index of T-Kernel/OS System Calls T
Page 19 and 20:
INDEX OF T-KERNEL/OS SYSTEM CALLS x
Page 21 and 22:
Index of T-Kernel/SM Extended SVC L
Page 23 and 24:
Index of T-Kernel/DS System Calls T
Page 25 and 26:
Chapter 1 T-Kernel Overview 1.1 Pos
Page 27 and 28:
1.2. SCALABILITY 3 • Middleware m
Page 29 and 30:
Chapter 2 Concepts Underlying the T
Page 31 and 32:
2.2. TASK STATES AND SCHEDULING RUL
Page 33 and 34:
2.2. TASK STATES AND SCHEDULING RUL
Page 35 and 36:
2.3. INTERRUPT HANDLING 11 preceden
Page 37 and 38:
2.5. SYSTEM STATES 13 Transient sta
Page 39 and 40:
2.7. MEMORY 15 which the upper and
Page 41 and 42:
Chapter 3 Common T-Kernel Specifica
Page 43 and 44:
3.2. SYSTEM CALLS 19 /* * Common co
Page 45 and 46:
3.2. SYSTEM CALLS 21 Ordinarily a f
Page 47 and 48:
3.3. HIGH-LEVEL LANGUAGE SUPPORT RO
Page 49 and 50:
Chapter 4 T-Kernel/OS Functions Thi
Page 51 and 52:
4.1. TASK MANAGEMENT FUNCTIONS 27 t
Page 53 and 54:
4.1. TASK MANAGEMENT FUNCTIONS 29 #
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
4.2. TASK-DEPENDENT SYNCHRONIZATION
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90: 4.2. TASK-DEPENDENT SYNCHRONIZATION
Page 91 and 92: 4.2. TASK-DEPENDENT SYNCHRONIZATION
Page 93 and 94: 4.3. TASK EXCEPTION HANDLING FUNCTI
Page 101 and 102: 4.4. SYNCHRONIZATION AND COMMUNICAT
Page 131 and 132: 4.5. EXTENDED SYNCHRONIZATION AND C
Page 139: 4.5. EXTENDED SYNCHRONIZATION AND C
Page 171 and 172: 4.6. MEMORY POOL MANAGEMENT FUNCTIO
Page 187 and 188: 4.7. TIME MANAGEMENT FUNCTIONS 163
Page 189 and 190: 4.7. TIME MANAGEMENT FUNCTIONS 165
Page 191 and 192:
4.7. TIME MANAGEMENT FUNCTIONS 167
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
4.8. INTERRUPT MANAGEMENT FUNCTIONS
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
4.9. SYSTEM MANAGEMENT FUNCTIONS 19
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
4.10. SUBSYSTEM MANAGEMENT FUNCTION
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Chapter 5 T-Kernel/SM Details of th
Page 245 and 246:
5.1. SYSTEM MEMORY MANAGEMENT FUNCT
Page 247 and 248:
5.2. ADDRESS SPACE MANAGEMENT FUNCT
Page 249 and 250:
5.2. ADDRESS SPACE MANAGEMENT FUNCT
Page 251 and 252:
5.3. DEVICE MANAGEMENT FUNCTIONS 22
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
5.5. IO PORT ACCESS SUPPORT FUNCTIO
Page 277 and 278:
5.7. SYSTEM CONFIGURATION INFORMATI
Page 279 and 280:
5.7. SYSTEM CONFIGURATION INFORMATI
Page 281:
5.8. SUBSYSTEM AND DEVICE DRIVER ST
Page 284 and 285:
260 CHAPTER 6. T-KERNEL/DS FUNCTION
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304 and 305:
Page 306 and 307:
Page 308 and 309:
284 CHAPTER 7. REFERENCE INT tevptn
Page 310 and 311:
286 CHAPTER 7. REFERENCE ER ercd =
Page 312 and 313:
288 CHAPTER 7. REFERENCE INT ct = t
Page 314:
290 CHAPTER 7. REFERENCE E OACV ERC
show all

T-Kernel Specification (1.B0.02)

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?