1: /*
   2:  * Copyright (c) 1986 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  *
   6:  *	@(#)kern_synch.c	1.5 (2.11BSD) 1999/9/13
   7:  */
   8: 
   9: #include "param.h"
  10: #include "../machine/seg.h"
  11: 
  12: #include "user.h"
  13: #include "proc.h"
  14: #include "buf.h"
  15: #include "signal.h"
  16: #include "signalvar.h"
  17: #include "vm.h"
  18: #include "kernel.h"
  19: #include "systm.h"
  20: 
  21: #define SQSIZE  16  /* Must be power of 2 */
  22: 
  23: #define HASH(x) (((int)x >> 5) & (SQSIZE - 1))
  24: #define SCHMAG  8/10
  25: 
  26: struct  proc *slpque[SQSIZE];
  27: 
  28: /*
  29:  * Recompute process priorities, once a second
  30:  */
  31: schedcpu()
  32: {
  33:     register struct proc *p;
  34:     register int a;
  35: 
  36:     wakeup((caddr_t)&lbolt);
  37:     for (p = allproc; p != NULL; p = p->p_nxt) {
  38:         if (p->p_time != 127)
  39:             p->p_time++;
  40:         /*
  41: 		 * this is where 2.11 does its real time alarms.  4.X uses
  42: 		 * timeouts, since it offers better than second resolution.
  43: 		 * Putting it here allows us to continue using use an int
  44: 		 * to store the number of ticks in the callout structure,
  45: 		 * since the kernel never has a timeout of greater than
  46: 		 * around 9 minutes.
  47: 		 */
  48:         if (p->p_realtimer.it_value && !--p->p_realtimer.it_value) {
  49:             psignal(p, SIGALRM);
  50:             p->p_realtimer.it_value = p->p_realtimer.it_interval;
  51:         }
  52:         if (p->p_stat == SSLEEP || p->p_stat == SSTOP)
  53:             if (p->p_slptime != 127)
  54:                 p->p_slptime++;
  55:         if (p->p_slptime > 1)
  56:             continue;
  57:         a = (p->p_cpu & 0377) * SCHMAG + p->p_nice;
  58:         if (a < 0)
  59:             a = 0;
  60:         if (a > 255)
  61:             a = 255;
  62:         p->p_cpu = a;
  63:         if (p->p_pri >= PUSER)
  64:             setpri(p);
  65:     }
  66:     vmmeter();
  67:     if (runin!=0) {
  68:         runin = 0;
  69:         wakeup((caddr_t)&runin);
  70:     }
  71:     ++runrun;           /* swtch at least once a second */
  72:     timeout(schedcpu, (caddr_t)0, hz);
  73: }
  74: 
  75: /*
  76:  * Recalculate the priority of a process after it has slept for a while.
  77:  */
  78: updatepri(p)
  79:     register struct proc *p;
  80: {
  81:     register int a = p->p_cpu & 0377;
  82: 
  83:     p->p_slptime--;     /* the first time was done in schedcpu */
  84:     while (a && --p->p_slptime)
  85:         a = (SCHMAG * a) /* + p->p_nice */;
  86:     if (a < 0)
  87:         a = 0;
  88:     if (a > 255)
  89:         a = 255;
  90:     p->p_cpu = a;
  91:     (void) setpri(p);
  92: }
  93: 
  94: /*
  95:  * General sleep call "borrowed" from 4.4BSD - the 'wmesg' parameter was
  96:  * removed due to data space concerns.  Sleeps at most timo/hz seconds
  97:  * 0 means no timeout). NOTE: timeouts in 2.11BSD use a signed int and
  98:  * thus can be at most 32767 'ticks' or about 540 seconds in the US with
  99:  * 60hz power (~650 seconds if 50hz power is being used).
 100:  *
 101:  * If 'pri' includes the PCATCH flag signals are checked before and after
 102:  * sleeping otherwise  signals are not checked.   Returns 0 if a wakeup was
 103:  * done, EWOULDBLOCK if the timeout expired, ERESTART if the current system
 104:  * call should be restarted, and EINTR if the system call should be
 105:  * interrupted and EINTR returned to the user process.
 106: */
 107: 
 108: int
 109: tsleep(ident, priority, timo)
 110:     caddr_t ident;
 111:     int priority;
 112:     u_short timo;
 113:     {
 114:     register struct proc *p = u.u_procp;
 115:     register struct proc **qp;
 116:     int s;
 117:     int sig, catch = priority & PCATCH;
 118:     void    endtsleep();
 119: 
 120:     s = splhigh();
 121:     if  (panicstr)
 122:         {
 123: /*
 124:  * After a panic just give interrupts a chance then just return.  Don't
 125:  * run any other procs (or panic again below) in case this is the idle
 126:  * process and already asleep.  The splnet should be spl0 if the network
 127:  * was being used but for now avoid network interrupts that might cause
 128:  * another panic.
 129: */
 130:         (void)_splnet();
 131:         noop();
 132:         splx(s);
 133:         return;
 134:         }
 135: #ifdef  DIAGNOSTIC
 136:     if  (ident == NULL || p->p_stat != SRUN)
 137:         panic("tsleep");
 138: #endif
 139:     p->p_wchan = ident;
 140:     p->p_slptime = 0;
 141:     p->p_pri = priority & PRIMASK;
 142:     qp = &slpque[HASH(ident)];
 143:     p->p_link = *qp;
 144:     *qp =p;
 145:     if  (timo)
 146:         timeout(endtsleep, (caddr_t)p, timo);
 147: /*
 148:  * We put outselves on the sleep queue and start the timeout before calling
 149:  * CURSIG as we could stop there and a wakeup or a SIGCONT (or both) could
 150:  * occur while we were stopped.  A SIGCONT would cause us to be marked SSLEEP
 151:  * without resuming us thus we must be ready for sleep when CURSIG is called.
 152:  * If the wakeup happens while we're stopped p->p_wchan will be 0 upon
 153:  * return from CURSIG.
 154: */
 155:     if  (catch)
 156:         {
 157:         p->p_flag |= P_SINTR;
 158:         if  (sig = CURSIG(p))
 159:             {
 160:             if  (p->p_wchan)
 161:                 unsleep(p);
 162:             p->p_stat = SRUN;
 163:             goto resume;
 164:             }
 165:         if  (p->p_wchan == 0)
 166:             {
 167:             catch = 0;
 168:             goto resume;
 169:             }
 170:         }
 171:     else
 172:         sig = 0;
 173:     p->p_stat = SSLEEP;
 174:     u.u_ru.ru_nvcsw++;
 175:     swtch();
 176: resume:
 177:     splx(s);
 178:     p->p_flag &= ~P_SINTR;
 179:     if  (p->p_flag & P_TIMEOUT)
 180:         {
 181:         p->p_flag &= ~P_TIMEOUT;
 182:         if  (sig == 0)
 183:             return(EWOULDBLOCK);
 184:         }
 185:     else if (timo)
 186:         untimeout(endtsleep, (caddr_t)p);
 187:     if  (catch && (sig != 0 || (sig = CURSIG(p))))
 188:         {
 189:         if  (u.u_sigintr & sigmask(sig))
 190:             return(EINTR);
 191:         return(ERESTART);
 192:         }
 193:     return(0);
 194:     }
 195: 
 196: /*
 197:  * Implement timeout for tsleep above.  If process hasn't been awakened
 198:  * (p_wchan non zero) then set timeout flag and undo the sleep.  If proc
 199:  * is stopped just unsleep so it will remain stopped.
 200: */
 201: 
 202: void
 203: endtsleep(p)
 204:     register struct proc *p;
 205:     {
 206:     register int    s;
 207: 
 208:     s = splhigh();
 209:     if  (p->p_wchan)
 210:         {
 211:         if  (p->p_stat == SSLEEP)
 212:             setrun(p);
 213:         else
 214:             unsleep(p);
 215:         p->p_flag |= P_TIMEOUT;
 216:         }
 217:     splx(s);
 218:     }
 219: 
 220: /*
 221:  * Give up the processor till a wakeup occurs on chan, at which time the
 222:  * process enters the scheduling queue at priority pri.
 223:  *
 224:  * This routine was rewritten to use 'tsleep'.  The  old behaviour of sleep
 225:  * being interruptible (if 'pri>PZERO') is emulated by setting PCATCH and
 226:  * then performing the 'longjmp' if the return value of 'tsleep' is
 227:  * ERESTART.
 228:  *
 229:  * Callers of this routine must be prepared for premature return, and check
 230:  * that the reason for sleeping has gone away.
 231:  */
 232: sleep(chan, pri)
 233:     caddr_t chan;
 234:     int pri;
 235:     {
 236:     register int priority = pri;
 237: 
 238:     if  (pri > PZERO)
 239:         priority |= PCATCH;
 240: 
 241:     u.u_error = tsleep(chan, priority, 0);
 242: /*
 243:  * sleep does not return anything.  If it was a non-interruptible sleep _or_
 244:  * a successful/normal sleep (one for which a wakeup was done) then return.
 245: */
 246:     if  ((priority & PCATCH) == 0 || (u.u_error == 0))
 247:         return;
 248: /*
 249:  * XXX - compatibility uglyness.
 250:  *
 251:  * The tsleep() above will leave one of the following in u_error:
 252:  *
 253:  * 0 - a wakeup was done, this is handled above
 254:  * EWOULDBLOCK - since no timeout was passed to tsleep we will not see this
 255:  * EINTR - put into u_error for trap.c to find (interrupted syscall)
 256:  * ERESTART - system call to be restared
 257: */
 258:     longjmp(u.u_procp->p_addr, &u.u_qsave);
 259:     /*NOTREACHED*/
 260:     }
 261: 
 262: /*
 263:  * Remove a process from its wait queue
 264:  */
 265: unsleep(p)
 266:     register struct proc *p;
 267: {
 268:     register struct proc **hp;
 269:     register int s;
 270: 
 271:     s = splhigh();
 272:     if (p->p_wchan) {
 273:         hp = &slpque[HASH(p->p_wchan)];
 274:         while (*hp != p)
 275:             hp = &(*hp)->p_link;
 276:         *hp = p->p_link;
 277:         p->p_wchan = 0;
 278:     }
 279:     splx(s);
 280: }
 281: 
 282: /*
 283:  * Wake up all processes sleeping on chan.
 284:  */
 285: wakeup(chan)
 286:     register caddr_t chan;
 287: {
 288:     register struct proc *p, **q;
 289:     struct proc **qp;
 290:     int s;
 291:     mapinfo map;
 292: 
 293:     /*
 294: 	 * Since we are called at interrupt time, must insure normal
 295: 	 * kernel mapping to access proc.
 296: 	 */
 297:     savemap(map);
 298:     s = splclock();
 299:     qp = &slpque[HASH(chan)];
 300: restart:
 301:     for (q = qp; p = *q; ) {
 302:         if (p->p_stat != SSLEEP && p->p_stat != SSTOP)
 303:             panic("wakeup");
 304:         if (p->p_wchan==chan) {
 305:             p->p_wchan = 0;
 306:             *q = p->p_link;
 307:             if (p->p_stat == SSLEEP) {
 308:                 /* OPTIMIZED INLINE EXPANSION OF setrun(p) */
 309:                 if (p->p_slptime > 1)
 310:                     updatepri(p);
 311:                 p->p_slptime = 0;
 312:                 p->p_stat = SRUN;
 313:                 if (p->p_flag & SLOAD)
 314:                     setrq(p);
 315:                 /*
 316: 				 * Since curpri is a usrpri,
 317: 				 * p->p_pri is always better than curpri.
 318: 				 */
 319:                 runrun++;
 320:                 if ((p->p_flag&SLOAD) == 0) {
 321:                     if (runout != 0) {
 322:                         runout = 0;
 323:                         wakeup((caddr_t)&runout);
 324:                     }
 325:                 }
 326:                 /* END INLINE EXPANSION */
 327:                 goto restart;
 328:             }
 329:             p->p_slptime = 0;
 330:         } else
 331:             q = &p->p_link;
 332:     }
 333:     splx(s);
 334:     restormap(map);
 335: }
 336: 
 337: /*
 338:  * Set the process running;
 339:  * arrange for it to be swapped in if necessary.
 340:  */
 341: setrun(p)
 342:     register struct proc *p;
 343: {
 344:     register int s;
 345: 
 346:     s = splhigh();
 347:     switch (p->p_stat) {
 348: 
 349:     case 0:
 350:     case SWAIT:
 351:     case SRUN:
 352:     case SZOMB:
 353:     default:
 354:         panic("setrun");
 355: 
 356:     case SSTOP:
 357:     case SSLEEP:
 358:         unsleep(p);     /* e.g. when sending signals */
 359:         break;
 360: 
 361:     case SIDL:
 362:         break;
 363:     }
 364:     if (p->p_slptime > 1)
 365:         updatepri(p);
 366:     p->p_stat = SRUN;
 367:     if (p->p_flag & SLOAD)
 368:         setrq(p);
 369:     splx(s);
 370:     if (p->p_pri < curpri)
 371:         runrun++;
 372:     if ((p->p_flag&SLOAD) == 0) {
 373:         if (runout != 0) {
 374:             runout = 0;
 375:             wakeup((caddr_t)&runout);
 376:         }
 377:     }
 378: }
 379: 
 380: /*
 381:  * Set user priority.
 382:  * The rescheduling flag (runrun)
 383:  * is set if the priority is better
 384:  * than the currently running process.
 385:  */
 386: setpri(pp)
 387:     register struct proc *pp;
 388: {
 389:     register int p;
 390: 
 391:     p = (pp->p_cpu & 0377)/16;
 392:     p += PUSER + pp->p_nice;
 393:     if (p > 127)
 394:         p = 127;
 395:     if (p < curpri)
 396:         runrun++;
 397:     pp->p_pri = p;
 398:     return (p);
 399: }
 400: 
 401: /*
 402:  * This routine is called to reschedule the CPU.  If the calling process is
 403:  * not in RUN state, arrangements for it to restart must have been made
 404:  * elsewhere, usually by calling via sleep.  There is a race here.  A process
 405:  * may become ready after it has been examined.  In this case, idle() will be
 406:  * called and will return in at most 1hz time, e.g. it's not worth putting an
 407:  * spl() in.
 408:  */
 409: swtch()
 410: {
 411:     register struct proc *p, *q;
 412:     register int n;
 413:     struct proc *pp, *pq;
 414:     int s;
 415: 
 416: #ifdef DIAGNOSTIC
 417:     extern struct buf *hasmap;
 418:     if (hasmap)
 419:         panic("swtch hasmap");
 420: #endif
 421: #ifdef UCB_METER
 422:     cnt.v_swtch++;
 423: #endif
 424:     /* If not the idle process, resume the idle process. */
 425:     if (u.u_procp != &proc[0]) {
 426:         if (setjmp(&u.u_rsave)) {
 427:             sureg();
 428:             return;
 429:         }
 430:         if (u.u_fpsaved == 0) {
 431:             savfp(&u.u_fps);
 432:             u.u_fpsaved = 1;
 433:         }
 434:         longjmp(proc[0].p_addr, &u.u_qsave);
 435:     }
 436:     /*
 437: 	 * The first save returns nonzero when proc 0 is resumed
 438: 	 * by another process (above); then the second is not done
 439: 	 * and the process-search loop is entered.
 440: 	 *
 441: 	 * The first save returns 0 when swtch is called in proc 0
 442: 	 * from sched().  The second save returns 0 immediately, so
 443: 	 * in this case too the process-search loop is entered.
 444: 	 * Thus when proc 0 is awakened by being made runnable, it will
 445: 	 * find itself and resume itself at rsave, and return to sched().
 446: 	 */
 447:     if (setjmp(&u.u_qsave)==0 && setjmp(&u.u_rsave))
 448:         return;
 449: loop:
 450:     s = splhigh();
 451:     noproc = 0;
 452:     runrun = 0;
 453: #ifdef DIAGNOSTIC
 454:     for (p = qs; p; p = p->p_link)
 455:         if (p->p_stat != SRUN)
 456:             panic("swtch SRUN");
 457: #endif
 458:     pp = NULL;
 459:     q = NULL;
 460:     n = 128;
 461:     /*
 462: 	 * search for highest-priority runnable process
 463: 	 */
 464:     for (p = qs; p; p = p->p_link) {
 465:         if (p->p_flag & SLOAD && p->p_pri < n) {
 466:             pp = p;
 467:             pq = q;
 468:             n = p->p_pri;
 469:         }
 470:         q = p;
 471:     }
 472:     /*
 473: 	 * if no process is runnable, idle.
 474: 	 */
 475:     p = pp;
 476:     if (p == NULL) {
 477:         idle();
 478:         goto loop;
 479:     }
 480:     if (pq)
 481:         pq->p_link = p->p_link;
 482:     else
 483:         qs = p->p_link;
 484:     curpri = n;
 485:     splx(s);
 486:     /*
 487: 	 * the rsave (ssave) contents are interpreted
 488: 	 * in the new address space
 489: 	 */
 490:     n = p->p_flag & SSWAP;
 491:     p->p_flag &= ~SSWAP;
 492:     longjmp(p->p_addr, n ? &u.u_ssave: &u.u_rsave);
 493: }
 494: 
 495: setrq(p)
 496:     register struct proc *p;
 497: {
 498:     register int s;
 499: 
 500:     s = splhigh();
 501: #ifdef DIAGNOSTIC
 502:     {           /* see if already on the run queue */
 503:         register struct proc *q;
 504: 
 505:         for (q = qs;q != NULL;q = q->p_link)
 506:             if (q == p)
 507:                 panic("setrq");
 508:     }
 509: #endif
 510:     p->p_link = qs;
 511:     qs = p;
 512:     splx(s);
 513: }
 514: 
 515: /*
 516:  * Remove runnable job from run queue.  This is done when a runnable job
 517:  * is swapped out so that it won't be selected in swtch().  It will be
 518:  * reinserted in the qs with setrq when it is swapped back in.
 519:  */
 520: remrq(p)
 521:     register struct proc *p;
 522: {
 523:     register struct proc *q;
 524:     register int s;
 525: 
 526:     s = splhigh();
 527:     if (p == qs)
 528:         qs = p->p_link;
 529:     else {
 530:         for (q = qs; q; q = q->p_link)
 531:             if (q->p_link == p) {
 532:                 q->p_link = p->p_link;
 533:                 goto done;
 534:             }
 535:             panic("remrq");
 536:     }
 537: done:
 538:     splx(s);
 539: }

Defined functions

endtsleep defined in line 202; used 3 times
remrq defined in line 520; used 1 times
schedcpu defined in line 31; used 2 times
setpri defined in line 386; used 5 times
setrq defined in line 495; used 6 times
sleep defined in line 232; used 93 times
unsleep defined in line 265; used 5 times
updatepri defined in line 78; used 2 times
wakeup defined in line 285; used 104 times

Defined variables

slpque defined in line 26; used 3 times

Defined macros

HASH defined in line 23; used 3 times
SCHMAG defined in line 24; used 2 times
SQSIZE defined in line 21; used 2 times
Last modified: 1999-09-16
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