1 #include "types.h" 2 #include "defs.h" 3 #include "param.h" 4 #include "memlayout.h" 5 #include "mmu.h" 6 #include "x86.h" 7 #include "proc.h" 8 #include "spinlock.h" 9 10 struct { 11 struct spinlock lock; 12 struct proc proc[NPROC]; 13 } ptable; 14 15 static struct proc *initproc; 16 17 int nextpid = 1; 18 extern void forkret(void); 19 extern void trapret(void); 20 21 static void wakeup1(void *chan); 22 23 void 24 pinit(void) 25 { 26 initlock(&ptable.lock, "ptable"); 27 } 28 29 //PAGEBREAK: 32 30 // Look in the process table for an UNUSED proc. 31 // If found, change state to EMBRYO and initialize 32 // state required to run in the kernel. 33 // Otherwise return 0. 34 // Must hold ptable.lock. 35 static struct proc* 36 allocproc(void) 37 { 38 struct proc *p; 39 char *sp; 40 41 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++) 42 if(p->state == UNUSED) 43 goto found; 44 return 0; 45 46 found: 47 p->state = EMBRYO; 48 p->pid = nextpid++; 49 50 // Allocate kernel stack. 51 if((p->kstack = kalloc()) == 0){ 52 p->state = UNUSED; 53 return 0; 54 } 55 sp = p->kstack + KSTACKSIZE; 56 57 // Leave room for trap frame. 58 sp -= sizeof *p->tf; 59 p->tf = (struct trapframe*)sp; 60 61 // Set up new context to start executing at forkret, 62 // which returns to trapret. 63 sp -= 4; 64 *(uint*)sp = (uint)trapret; 65 66 sp -= sizeof *p->context; 67 p->context = (struct context*)sp; 68 memset(p->context, 0, sizeof *p->context); 69 p->context->eip = (uint)forkret; 70 71 return p; 72 } 73 74 //PAGEBREAK: 32 75 // Set up first user process. 76 void 77 userinit(void) 78 { 79 struct proc *p; 80 extern char _binary_initcode_start[], _binary_initcode_size[]; 81 82 acquire(&ptable.lock); 83 84 p = allocproc(); 85 initproc = p; 86 if((p->pgdir = setupkvm()) == 0) 87 panic("userinit: out of memory?"); 88 inituvm(p->pgdir, _binary_initcode_start, (int)_binary_initcode_size); 89 p->sz = PGSIZE; 90 memset(p->tf, 0, sizeof(*p->tf)); 91 p->tf->cs = (SEG_UCODE << 3) | DPL_USER; 92 p->tf->ds = (SEG_UDATA << 3) | DPL_USER; 93 p->tf->es = p->tf->ds; 94 p->tf->ss = p->tf->ds; 95 p->tf->eflags = FL_IF; 96 p->tf->esp = PGSIZE; 97 p->tf->eip = 0; // beginning of initcode.S 98 99 safestrcpy(p->name, "initcode", sizeof(p->name)); 100 p->cwd = namei("/"); 101 102 p->state = RUNNABLE; 103 104 release(&ptable.lock); 105 } 106 107 // Grow current process's memory by n bytes. 108 // Return 0 on success, -1 on failure. 109 int 110 growproc(int n) 111 { 112 uint sz; 113 114 sz = proc->sz; 115 if(n > 0){ 116 if((sz = allocuvm(proc->pgdir, sz, sz + n)) == 0) 117 return -1; 118 } else if(n < 0){ 119 if((sz = deallocuvm(proc->pgdir, sz, sz + n)) == 0) 120 return -1; 121 } 122 proc->sz = sz; 123 switchuvm(proc); 124 return 0; 125 } 126 127 // Create a new process copying p as the parent. 128 // Sets up stack to return as if from system call. 129 // Caller must set state of returned proc to RUNNABLE. 130 int 131 fork(void) 132 { 133 int i, pid; 134 struct proc *np; 135 136 acquire(&ptable.lock); 137 138 // Allocate process. 139 if((np = allocproc()) == 0){ 140 release(&ptable.lock); 141 return -1; 142 } 143 144 // Copy process state from p. 145 if((np->pgdir = copyuvm(proc->pgdir, proc->sz)) == 0){ 146 kfree(np->kstack); 147 np->kstack = 0; 148 np->state = UNUSED; 149 release(&ptable.lock); 150 return -1; 151 } 152 np->sz = proc->sz; 153 np->parent = proc; 154 *np->tf = *proc->tf; 155 156 // Clear %eax so that fork returns 0 in the child. 157 np->tf->eax = 0; 158 159 for(i = 0; i < NOFILE; i++) 160 if(proc->ofile[i]) 161 np->ofile[i] = filedup(proc->ofile[i]); 162 np->cwd = idup(proc->cwd); 163 164 safestrcpy(np->name, proc->name, sizeof(proc->name)); 165 166 pid = np->pid; 167 168 np->state = RUNNABLE; 169 170 release(&ptable.lock); 171 172 return pid; 173 } 174 175 // Exit the current process. Does not return. 176 // An exited process remains in the zombie state 177 // until its parent calls wait() to find out it exited. 178 void 179 exit(void) 180 { 181 struct proc *p; 182 int fd; 183 184 if(proc == initproc) 185 panic("init exiting"); 186 187 // Close all open files. 188 for(fd = 0; fd < NOFILE; fd++){ 189 if(proc->ofile[fd]){ 190 fileclose(proc->ofile[fd]); 191 proc->ofile[fd] = 0; 192 } 193 } 194 195 begin_op(); 196 iput(proc->cwd); 197 end_op(); 198 proc->cwd = 0; 199 200 acquire(&ptable.lock); 201 202 // Parent might be sleeping in wait(). 203 wakeup1(proc->parent); 204 205 // Pass abandoned children to init. 206 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ 207 if(p->parent == proc){ 208 p->parent = initproc; 209 if(p->state == ZOMBIE) 210 wakeup1(initproc); 211 } 212 } 213 214 // Jump into the scheduler, never to return. 215 proc->state = ZOMBIE; 216 sched(); 217 panic("zombie exit"); 218 } 219 220 // Wait for a child process to exit and return its pid. 221 // Return -1 if this process has no children. 222 int 223 wait(void) 224 { 225 struct proc *p; 226 int havekids, pid; 227 228 acquire(&ptable.lock); 229 for(;;){ 230 // Scan through table looking for zombie children. 231 havekids = 0; 232 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ 233 if(p->parent != proc) 234 continue; 235 havekids = 1; 236 if(p->state == ZOMBIE){ 237 // Found one. 238 pid = p->pid; 239 kfree(p->kstack); 240 p->kstack = 0; 241 freevm(p->pgdir); 242 p->pid = 0; 243 p->parent = 0; 244 p->name[0] = 0; 245 p->killed = 0; 246 p->state = UNUSED; 247 release(&ptable.lock); 248 return pid; 249 } 250 } 251 252 // No point waiting if we don't have any children. 253 if(!havekids || proc->killed){ 254 release(&ptable.lock); 255 return -1; 256 } 257 258 // Wait for children to exit. (See wakeup1 call in proc_exit.) 259 sleep(proc, &ptable.lock); //DOC: wait-sleep 260 } 261 } 262 263 //PAGEBREAK: 42 264 // Per-CPU process scheduler. 265 // Each CPU calls scheduler() after setting itself up. 266 // Scheduler never returns. It loops, doing: 267 // - choose a process to run 268 // - swtch to start running that process 269 // - eventually that process transfers control 270 // via swtch back to the scheduler. 271 void 272 scheduler(void) 273 { 274 struct proc *p; 275 276 for(;;){ 277 // Enable interrupts on this processor. 278 sti(); 279 280 // Loop over process table looking for process to run. 281 acquire(&ptable.lock); 282 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ 283 if(p->state != RUNNABLE) 284 continue; 285 286 // Switch to chosen process. It is the process's job 287 // to release ptable.lock and then reacquire it 288 // before jumping back to us. 289 proc = p; 290 switchuvm(p); 291 p->state = RUNNING; 292 swtch(&cpu->scheduler, p->context); 293 switchkvm(); 294 295 // Process is done running for now. 296 // It should have changed its p->state before coming back. 297 proc = 0; 298 } 299 release(&ptable.lock); 300 301 } 302 } 303 304 // Enter scheduler. Must hold only ptable.lock 305 // and have changed proc->state. 306 void 307 sched(void) 308 { 309 int intena; 310 311 if(!holding(&ptable.lock)) 312 panic("sched ptable.lock"); 313 if(cpu->ncli != 1) 314 panic("sched locks"); 315 if(proc->state == RUNNING) 316 panic("sched running"); 317 if(readeflags()&FL_IF) 318 panic("sched interruptible"); 319 intena = cpu->intena; 320 swtch(&proc->context, cpu->scheduler); 321 cpu->intena = intena; 322 } 323 324 // Give up the CPU for one scheduling round. 325 void 326 yield(void) 327 { 328 acquire(&ptable.lock); //DOC: yieldlock 329 proc->state = RUNNABLE; 330 sched(); 331 release(&ptable.lock); 332 } 333 334 // A fork child's very first scheduling by scheduler() 335 // will swtch here. "Return" to user space. 336 void 337 forkret(void) 338 { 339 static int first = 1; 340 // Still holding ptable.lock from scheduler. 341 release(&ptable.lock); 342 343 if (first) { 344 // Some initialization functions must be run in the context 345 // of a regular process (e.g., they call sleep), and thus cannot 346 // be run from main(). 347 first = 0; 348 iinit(ROOTDEV); 349 initlog(ROOTDEV); 350 } 351 352 // Return to "caller", actually trapret (see allocproc). 353 } 354 355 // Atomically release lock and sleep on chan. 356 // Reacquires lock when awakened. 357 void 358 sleep(void *chan, struct spinlock *lk) 359 { 360 if(proc == 0) 361 panic("sleep"); 362 363 if(lk == 0) 364 panic("sleep without lk"); 365 366 // Must acquire ptable.lock in order to 367 // change p->state and then call sched. 368 // Once we hold ptable.lock, we can be 369 // guaranteed that we won't miss any wakeup 370 // (wakeup runs with ptable.lock locked), 371 // so it's okay to release lk. 372 if(lk != &ptable.lock){ //DOC: sleeplock0 373 acquire(&ptable.lock); //DOC: sleeplock1 374 release(lk); 375 } 376 377 // Go to sleep. 378 proc->chan = chan; 379 proc->state = SLEEPING; 380 sched(); 381 382 // Tidy up. 383 proc->chan = 0; 384 385 // Reacquire original lock. 386 if(lk != &ptable.lock){ //DOC: sleeplock2 387 release(&ptable.lock); 388 acquire(lk); 389 } 390 } 391 392 //PAGEBREAK! 393 // Wake up all processes sleeping on chan. 394 // The ptable lock must be held. 395 static void 396 wakeup1(void *chan) 397 { 398 struct proc *p; 399 400 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++) 401 if(p->state == SLEEPING && p->chan == chan) 402 p->state = RUNNABLE; 403 } 404 405 // Wake up all processes sleeping on chan. 406 void 407 wakeup(void *chan) 408 { 409 acquire(&ptable.lock); 410 wakeup1(chan); 411 release(&ptable.lock); 412 } 413 414 // Kill the process with the given pid. 415 // Process won't exit until it returns 416 // to user space (see trap in trap.c). 417 int 418 kill(int pid) 419 { 420 struct proc *p; 421 422 acquire(&ptable.lock); 423 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ 424 if(p->pid == pid){ 425 p->killed = 1; 426 // Wake process from sleep if necessary. 427 if(p->state == SLEEPING) 428 p->state = RUNNABLE; 429 release(&ptable.lock); 430 return 0; 431 } 432 } 433 release(&ptable.lock); 434 return -1; 435 } 436 437 //PAGEBREAK: 36 438 // Print a process listing to console. For debugging. 439 // Runs when user types ^P on console. 440 // No lock to avoid wedging a stuck machine further. 441 void 442 procdump(void) 443 { 444 static char *states[] = { 445 [UNUSED] "unused", 446 [EMBRYO] "embryo", 447 [SLEEPING] "sleep ", 448 [RUNNABLE] "runble", 449 [RUNNING] "run ", 450 [ZOMBIE] "zombie" 451 }; 452 int i; 453 struct proc *p; 454 char *state; 455 uint pc[10]; 456 457 for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ 458 if(p->state == UNUSED) 459 continue; 460 if(p->state >= 0 && p->state < NELEM(states) && states[p->state]) 461 state = states[p->state]; 462 else 463 state = "???"; 464 cprintf("%d %s %s", p->pid, state, p->name); 465 if(p->state == SLEEPING){ 466 getcallerpcs((uint*)p->context->ebp+2, pc); 467 for(i=0; i<10 && pc[i] != 0; i++) 468 cprintf(" %p", pc[i]); 469 } 470 cprintf("\n"); 471 } 472 } 473