4.3BSD - /usr/src/sys/sys/kern_synch.c

   1: /*
   2:  * Copyright (c) 1982, 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	7.1 (Berkeley) 6/5/86
   7:  */
   8: 
   9: #include "../machine/pte.h"
  10: 
  11: #include "param.h"
  12: #include "systm.h"
  13: #include "dir.h"
  14: #include "user.h"
  15: #include "proc.h"
  16: #include "file.h"
  17: #include "inode.h"
  18: #include "vm.h"
  19: #include "kernel.h"
  20: #include "buf.h"
  21: 
  22: #ifdef vax
  23: #include "../vax/mtpr.h"    /* XXX */
  24: #endif
  25: /*
  26:  * Force switch among equal priority processes every 100ms.
  27:  */
  28: roundrobin()
  29: {
  30: 
  31:     runrun++;
  32:     aston();
  33:     timeout(roundrobin, (caddr_t)0, hz / 10);
  34: }
  35: 
  36: /* fraction for digital decay to forget 90% of usage in 5*loadav sec */
  37: #define filter(loadav) ((2 * (loadav)) / (2 * (loadav) + 1))
  38: 
  39: double  ccpu = 0.95122942450071400909;      /* exp(-1/20) */
  40: 
  41: /*
  42:  * Recompute process priorities, once a second
  43:  */
  44: schedcpu()
  45: {
  46:     register double ccpu1 = (1.0 - ccpu) / (double)hz;
  47:     register struct proc *p;
  48:     register int s, a;
  49:     float scale = filter(avenrun[0]);
  50: 
  51:     wakeup((caddr_t)&lbolt);
  52:     for (p = allproc; p != NULL; p = p->p_nxt) {
  53:         if (p->p_time != 127)
  54:             p->p_time++;
  55:         if (p->p_stat==SSLEEP || p->p_stat==SSTOP)
  56:             if (p->p_slptime != 127)
  57:                 p->p_slptime++;
  58:         /*
  59: 		 * If the process has slept the entire second,
  60: 		 * stop recalculating its priority until it wakes up.
  61: 		 */
  62:         if (p->p_slptime > 1) {
  63:             p->p_pctcpu *= ccpu;
  64:             continue;
  65:         }
  66:         /*
  67: 		 * p_pctcpu is only for ps.
  68: 		 */
  69:         p->p_pctcpu = ccpu * p->p_pctcpu + ccpu1 * p->p_cpticks;
  70:         p->p_cpticks = 0;
  71:         a = (int) (scale * (p->p_cpu & 0377)) + p->p_nice;
  72:         if (a < 0)
  73:             a = 0;
  74:         if (a > 255)
  75:             a = 255;
  76:         p->p_cpu = a;
  77:         (void) setpri(p);
  78:         s = splhigh();  /* prevent state changes */
  79:         if (p->p_pri >= PUSER) {
  80: #define PPQ (128 / NQS)
  81:             if ((p != u.u_procp || noproc) &&
  82:                 p->p_stat == SRUN &&
  83:                 (p->p_flag & SLOAD) &&
  84:                 (p->p_pri / PPQ) != (p->p_usrpri / PPQ)) {
  85:                 remrq(p);
  86:                 p->p_pri = p->p_usrpri;
  87:                 setrq(p);
  88:             } else
  89:                 p->p_pri = p->p_usrpri;
  90:         }
  91:         splx(s);
  92:     }
  93:     vmmeter();
  94:     if (runin!=0) {
  95:         runin = 0;
  96:         wakeup((caddr_t)&runin);
  97:     }
  98:     if (bclnlist != NULL)
  99:         wakeup((caddr_t)&proc[2]);
 100:     timeout(schedcpu, (caddr_t)0, hz);
 101: }
 102: 
 103: /*
 104:  * Recalculate the priority of a process after it has slept for a while.
 105:  */
 106: updatepri(p)
 107:     register struct proc *p;
 108: {
 109:     register int a = p->p_cpu & 0377;
 110:     float scale = filter(avenrun[0]);
 111: 
 112:     p->p_slptime--;     /* the first time was done in schedcpu */
 113:     while (a && --p->p_slptime)
 114:         a = (int) (scale * a) /* + p->p_nice */;
 115:     if (a < 0)
 116:         a = 0;
 117:     if (a > 255)
 118:         a = 255;
 119:     p->p_cpu = a;
 120:     (void) setpri(p);
 121: }
 122: 
 123: #define SQSIZE 0100 /* Must be power of 2 */
 124: #define HASH(x) (( (int) x >> 5) & (SQSIZE-1))
 125: struct slpque {
 126:     struct proc *sq_head;
 127:     struct proc **sq_tailp;
 128: } slpque[SQSIZE];
 129: 
 130: /*
 131:  * Give up the processor till a wakeup occurs
 132:  * on chan, at which time the process
 133:  * enters the scheduling queue at priority pri.
 134:  * The most important effect of pri is that when
 135:  * pri<=PZERO a signal cannot disturb the sleep;
 136:  * if pri>PZERO signals will be processed.
 137:  * Callers of this routine must be prepared for
 138:  * premature return, and check that the reason for
 139:  * sleeping has gone away.
 140:  */
 141: sleep(chan, pri)
 142:     caddr_t chan;
 143:     int pri;
 144: {
 145:     register struct proc *rp;
 146:     register struct slpque *qp;
 147:     register s;
 148: 
 149:     rp = u.u_procp;
 150:     s = splhigh();
 151:     if (panicstr) {
 152:         /*
 153: 		 * After a panic, just give interrupts a chance,
 154: 		 * then just return; don't run any other procs
 155: 		 * or panic below, in case this is the idle process
 156: 		 * and already asleep.
 157: 		 * The splnet should be spl0 if the network was being used
 158: 		 * by the filesystem, but for now avoid network interrupts
 159: 		 * that might cause another panic.
 160: 		 */
 161:         (void) splnet();
 162:         splx(s);
 163:         return;
 164:     }
 165:     if (chan==0 || rp->p_stat != SRUN || rp->p_rlink)
 166:         panic("sleep");
 167:     rp->p_wchan = chan;
 168:     rp->p_slptime = 0;
 169:     rp->p_pri = pri;
 170:     qp = &slpque[HASH(chan)];
 171:     if (qp->sq_head == 0)
 172:         qp->sq_head = rp;
 173:     else
 174:         *qp->sq_tailp = rp;
 175:     *(qp->sq_tailp = &rp->p_link) = 0;
 176:     if (pri > PZERO) {
 177:         /*
 178: 		 * If we stop in issig(), wakeup may already have happened
 179: 		 * when we return (rp->p_wchan will then be 0).
 180: 		 */
 181:         if (ISSIG(rp)) {
 182:             if (rp->p_wchan)
 183:                 unsleep(rp);
 184:             rp->p_stat = SRUN;
 185:             (void) spl0();
 186:             goto psig;
 187:         }
 188:         if (rp->p_wchan == 0)
 189:             goto out;
 190:         rp->p_stat = SSLEEP;
 191:         (void) spl0();
 192:         u.u_ru.ru_nvcsw++;
 193:         swtch();
 194:         if (ISSIG(rp))
 195:             goto psig;
 196:     } else {
 197:         rp->p_stat = SSLEEP;
 198:         (void) spl0();
 199:         u.u_ru.ru_nvcsw++;
 200:         swtch();
 201:     }
 202:     curpri = rp->p_usrpri;
 203: out:
 204:     splx(s);
 205:     return;
 206: 
 207:     /*
 208: 	 * If priority was low (>PZERO) and
 209: 	 * there has been a signal, execute non-local goto through
 210: 	 * u.u_qsave, aborting the system call in progress (see trap.c)
 211: 	 */
 212: psig:
 213:     longjmp(&u.u_qsave);
 214:     /*NOTREACHED*/
 215: }
 216: 
 217: /*
 218:  * Remove a process from its wait queue
 219:  */
 220: unsleep(p)
 221:     register struct proc *p;
 222: {
 223:     register struct slpque *qp;
 224:     register struct proc **hp;
 225:     int s;
 226: 
 227:     s = splhigh();
 228:     if (p->p_wchan) {
 229:         hp = &(qp = &slpque[HASH(p->p_wchan)])->sq_head;
 230:         while (*hp != p)
 231:             hp = &(*hp)->p_link;
 232:         *hp = p->p_link;
 233:         if (qp->sq_tailp == &p->p_link)
 234:             qp->sq_tailp = hp;
 235:         p->p_wchan = 0;
 236:     }
 237:     splx(s);
 238: }
 239: 
 240: /*
 241:  * Wake up all processes sleeping on chan.
 242:  */
 243: wakeup(chan)
 244:     register caddr_t chan;
 245: {
 246:     register struct slpque *qp;
 247:     register struct proc *p, **q;
 248:     int s;
 249: 
 250:     s = splhigh();
 251:     qp = &slpque[HASH(chan)];
 252: restart:
 253:     for (q = &qp->sq_head; p = *q; ) {
 254:         if (p->p_rlink || p->p_stat != SSLEEP && p->p_stat != SSTOP)
 255:             panic("wakeup");
 256:         if (p->p_wchan==chan) {
 257:             p->p_wchan = 0;
 258:             *q = p->p_link;
 259:             if (qp->sq_tailp == &p->p_link)
 260:                 qp->sq_tailp = q;
 261:             if (p->p_stat == SSLEEP) {
 262:                 /* OPTIMIZED INLINE EXPANSION OF setrun(p) */
 263:                 if (p->p_slptime > 1)
 264:                     updatepri(p);
 265:                 p->p_slptime = 0;
 266:                 p->p_stat = SRUN;
 267:                 if (p->p_flag & SLOAD)
 268:                     setrq(p);
 269:                 /*
 270: 				 * Since curpri is a usrpri,
 271: 				 * p->p_pri is always better than curpri.
 272: 				 */
 273:                 runrun++;
 274:                 aston();
 275:                 if ((p->p_flag&SLOAD) == 0) {
 276:                     if (runout != 0) {
 277:                         runout = 0;
 278:                         wakeup((caddr_t)&runout);
 279:                     }
 280:                     wantin++;
 281:                 }
 282:                 /* END INLINE EXPANSION */
 283:                 goto restart;
 284:             }
 285:             p->p_slptime = 0;
 286:         } else
 287:             q = &p->p_link;
 288:     }
 289:     splx(s);
 290: }
 291: 
 292: /*
 293:  * Initialize the (doubly-linked) run queues
 294:  * to be empty.
 295:  */
 296: rqinit()
 297: {
 298:     register int i;
 299: 
 300:     for (i = 0; i < NQS; i++)
 301:         qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i];
 302: }
 303: 
 304: /*
 305:  * Set the process running;
 306:  * arrange for it to be swapped in if necessary.
 307:  */
 308: setrun(p)
 309:     register struct proc *p;
 310: {
 311:     register int s;
 312: 
 313:     s = splhigh();
 314:     switch (p->p_stat) {
 315: 
 316:     case 0:
 317:     case SWAIT:
 318:     case SRUN:
 319:     case SZOMB:
 320:     default:
 321:         panic("setrun");
 322: 
 323:     case SSTOP:
 324:     case SSLEEP:
 325:         unsleep(p);     /* e.g. when sending signals */
 326:         break;
 327: 
 328:     case SIDL:
 329:         break;
 330:     }
 331:     if (p->p_slptime > 1)
 332:         updatepri(p);
 333:     p->p_stat = SRUN;
 334:     if (p->p_flag & SLOAD)
 335:         setrq(p);
 336:     splx(s);
 337:     if (p->p_pri < curpri) {
 338:         runrun++;
 339:         aston();
 340:     }
 341:     if ((p->p_flag&SLOAD) == 0) {
 342:         if (runout != 0) {
 343:             runout = 0;
 344:             wakeup((caddr_t)&runout);
 345:         }
 346:         wantin++;
 347:     }
 348: }
 349: 
 350: /*
 351:  * Set user priority.
 352:  * The rescheduling flag (runrun)
 353:  * is set if the priority is better
 354:  * than the currently running process.
 355:  */
 356: setpri(pp)
 357:     register struct proc *pp;
 358: {
 359:     register int p;
 360: 
 361:     p = (pp->p_cpu & 0377)/4;
 362:     p += PUSER + 2 * pp->p_nice;
 363:     if (pp->p_rssize > pp->p_maxrss && freemem < desfree)
 364:         p += 2*4;   /* effectively, nice(4) */
 365:     if (p > 127)
 366:         p = 127;
 367:     if (p < curpri) {
 368:         runrun++;
 369:         aston();
 370:     }
 371:     pp->p_usrpri = p;
 372:     return (p);
 373: }

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