sys/src/9/port/proc.c

   1 #include        <u.h>
   2 #include        "../port/lib.h"
   3 #include        "mem.h"
   4 #include        "dat.h"
   5 #include        "fns.h"
   6 #include        "../port/error.h"
   7 #include        "edf.h"
   8 #include        <trace.h>
   9
  10 int     schedgain = 30; /* units in seconds */
  11 int     nrdy;
  12
  13 void updatecpu(Proc*);
  14 int reprioritize(Proc*);
  15
  16 ulong   delayedscheds;  /* statistics */
  17 long skipscheds;
  18 long preempts;
  19 ulong load;
  20
  21 static struct Procalloc
  22 {
  23         Lock;
  24         Proc*   ht[128];
  25         Proc*   arena;
  26         Proc*   free;
  27 } procalloc;
  28
  29 enum
  30 {
  31         Q=10,
  32         DQ=4,
  33         Scaling=2,
  34 };
  35
  36 Schedq  runq[Nrq];
  37 ulong   runvec;
  38
  39 char *statename[] =
  40 {       /* BUG: generate automatically */
  41         "Dead",
  42         "Moribund",
  43         "Ready",
  44         "Scheding",
  45         "Running",
  46         "Queueing",
  47         "QueueingR",
  48         "QueueingW",
  49         "Wakeme",
  50         "Broken",
  51         "Stopped",
  52         "Rendez",
  53         "Waitrelease",
  54 };
  55
  56 static void pidfree(Proc*);
  57 static void rebalance(void);
  58
  59 /*
  60  * Always splhi()'ed.
  61  */
  62 void
  63 schedinit(void)         /* never returns */
  64 {
  65         Edf *e;
  66
  67         setlabel(&m->sched);
  68         if(up != nil) {
  69                 if((e = up->edf) != nil && (e->flags & Admitted))
  70                         edfrecord(up);
  71                 m->proc = nil;
  72                 switch(up->state) {
  73                 case Running:
  74                         ready(up);
  75                         break;
  76                 case Moribund:
  77                         up->state = Dead;
  78                         edfstop(up);
  79                         if(up->edf != nil)
  80                                 free(up->edf);
  81                         up->edf = nil;
  82
  83                         /*
  84                          * Holding locks from pexit:
  85                          *      procalloc
  86                          *      palloc
  87                          */
  88                         mmurelease(up);
  89                         unlock(&palloc);
  90
  91                         up->mach = nil;
  92                         updatecpu(up);
  93
  94                         up->qnext = procalloc.free;
  95                         procalloc.free = up;
  96
  97                         /* proc is free now, make sure unlock() wont touch it */
  98                         up = procalloc.Lock.p = nil;
  99                         unlock(&procalloc);
 100                         sched();
 101                 }
 102                 up->mach = nil;
 103                 updatecpu(up);
 104                 up = nil;
 105         }
 106         sched();
 107 }
 108
 109 /*
 110  *  If changing this routine, look also at sleep().  It
 111  *  contains a copy of the guts of sched().
 112  */
 113 void
 114 sched(void)
 115 {
 116         Proc *p;
 117
 118         if(m->ilockdepth)
 119                 panic("cpu%d: ilockdepth %d, last lock %#p at %#p, sched called from %#p",
 120                         m->machno,
 121                         m->ilockdepth,
 122                         up != nil ? up->lastilock: nil,
 123                         (up != nil && up->lastilock != nil) ? up->lastilock->pc: 0,
 124                         getcallerpc(&p+2));
 125         if(up != nil) {
 126                 /*
 127                  * Delay the sched until the process gives up the locks
 128                  * it is holding.  This avoids dumb lock loops.
 129                  * Don't delay if the process is Moribund.
 130                  * It called sched to die.
 131                  * But do sched eventually.  This avoids a missing unlock
 132                  * from hanging the entire kernel.
 133                  * But don't reschedule procs holding palloc or procalloc.
 134                  * Those are far too important to be holding while asleep.
 135                  *
 136                  * This test is not exact.  There can still be a few instructions
 137                  * in the middle of taslock when a process holds a lock
 138                  * but Lock.p has not yet been initialized.
 139                  */
 140                 if(up->nlocks)
 141                 if(up->state != Moribund)
 142                 if(up->delaysched < 20
 143                 || palloc.Lock.p == up
 144                 || procalloc.Lock.p == up){
 145                         up->delaysched++;
 146                         delayedscheds++;
 147                         return;
 148                 }
 149                 up->delaysched = 0;
 150
 151                 splhi();
 152
 153                 /* statistics */
 154                 m->cs++;
 155
 156                 procsave(up);
 157                 if(setlabel(&up->sched)){
 158                         procrestore(up);
 159                         spllo();
 160                         return;
 161                 }
 162                 gotolabel(&m->sched);
 163         }
 164         p = runproc();
 165         if(p->edf == nil){
 166                 updatecpu(p);
 167                 p->priority = reprioritize(p);
 168         }
 169         if(p != m->readied)
 170                 m->schedticks = m->ticks + HZ/10;
 171         m->readied = nil;
 172         up = p;
 173         up->state = Running;
 174         up->mach = MACHP(m->machno);
 175         m->proc = up;
 176         mmuswitch(up);
 177         gotolabel(&up->sched);
 178 }
 179
 180 int
 181 anyready(void)
 182 {
 183         return runvec;
 184 }
 185
 186 int
 187 anyhigher(void)
 188 {
 189         return runvec & ~((1<<(up->priority+1))-1);
 190 }
 191
 192 /*
 193  *  here once per clock tick to see if we should resched
 194  */
 195 void
 196 hzsched(void)
 197 {
 198         /* once a second, rebalance will reprioritize ready procs */
 199         if(m->machno == 0)
 200                 rebalance();
 201
 202         /* unless preempted, get to run for at least 100ms */
 203         if(anyhigher()
 204         || (!up->fixedpri && m->ticks > m->schedticks && anyready())){
 205                 m->readied = nil;       /* avoid cooperative scheduling */
 206                 up->delaysched++;
 207         }
 208 }
 209
 210 /*
 211  *  here at the end of non-clock interrupts to see if we should preempt the
 212  *  current process.  Returns 1 if preempted, 0 otherwise.
 213  */
 214 int
 215 preempted(void)
 216 {
 217         if(up != nil && up->state == Running)
 218         if(up->preempted == 0)
 219         if(anyhigher())
 220         if(!active.exiting){
 221                 m->readied = nil;       /* avoid cooperative scheduling */
 222                 up->preempted = 1;
 223                 sched();
 224                 splhi();
 225                 up->preempted = 0;
 226                 return 1;
 227         }
 228         return 0;
 229 }
 230
 231 /*
 232  * Update the cpu time average for this particular process,
 233  * which is about to change from up -> not up or vice versa.
 234  * p->lastupdate is the last time an updatecpu happened.
 235  *
 236  * The cpu time average is a decaying average that lasts
 237  * about D clock ticks.  D is chosen to be approximately
 238  * the cpu time of a cpu-intensive "quick job".  A job has to run
 239  * for approximately D clock ticks before we home in on its
 240  * actual cpu usage.  Thus if you manage to get in and get out
 241  * quickly, you won't be penalized during your burst.  Once you
 242  * start using your share of the cpu for more than about D
 243  * clock ticks though, your p->cpu hits 1000 (1.0) and you end up
 244  * below all the other quick jobs.  Interactive tasks, because
 245  * they basically always use less than their fair share of cpu,
 246  * will be rewarded.
 247  *
 248  * If the process has not been running, then we want to
 249  * apply the filter
 250  *
 251  *      cpu = cpu * (D-1)/D
 252  *
 253  * n times, yielding
 254  *
 255  *      cpu = cpu * ((D-1)/D)^n
 256  *
 257  * but D is big enough that this is approximately
 258  *
 259  *      cpu = cpu * (D-n)/D
 260  *
 261  * so we use that instead.
 262  *
 263  * If the process has been running, we apply the filter to
 264  * 1 - cpu, yielding a similar equation.  Note that cpu is
 265  * stored in fixed point (* 1000).
 266  *
 267  * Updatecpu must be called before changing up, in order
 268  * to maintain accurate cpu usage statistics.  It can be called
 269  * at any time to bring the stats for a given proc up-to-date.
 270  */
 271 void
 272 updatecpu(Proc *p)
 273 {
 274         int n, t, ocpu;
 275         int D = schedgain*HZ*Scaling;
 276
 277         if(p->edf != nil)
 278                 return;
 279
 280         t = MACHP(0)->ticks*Scaling + Scaling/2;
 281         n = t - p->lastupdate;
 282         p->lastupdate = t;
 283
 284         if(n == 0)
 285                 return;
 286         if(n > D)
 287                 n = D;
 288
 289         ocpu = p->cpu;
 290         if(p != up)
 291                 p->cpu = (ocpu*(D-n))/D;
 292         else{
 293                 t = 1000 - ocpu;
 294                 t = (t*(D-n))/D;
 295                 p->cpu = 1000 - t;
 296         }
 297
 298 //iprint("pid %d %s for %d cpu %d -> %d\n", p->pid,p==up?"active":"inactive",n, ocpu,p->cpu);
 299 }
 300
 301 /*
 302  * On average, p has used p->cpu of a cpu recently.
 303  * Its fair share is conf.nmach/m->load of a cpu.  If it has been getting
 304  * too much, penalize it.  If it has been getting not enough, reward it.
 305  * I don't think you can get much more than your fair share that
 306  * often, so most of the queues are for using less.  Having a priority
 307  * of 3 means you're just right.  Having a higher priority (up to p->basepri)
 308  * means you're not using as much as you could.
 309  */
 310 int
 311 reprioritize(Proc *p)
 312 {
 313         int fairshare, n, load, ratio;
 314
 315         load = MACHP(0)->load;
 316         if(load == 0)
 317                 return p->basepri;
 318
 319         /*
 320          * fairshare = 1.000 * conf.nmach * 1.000/load,
 321          * except the decimal point is moved three places
 322          * on both load and fairshare.
 323          */
 324         fairshare = (conf.nmach*1000*1000)/load;
 325         n = p->cpu;
 326         if(n == 0)
 327                 n = 1;
 328         ratio = (fairshare+n/2) / n;
 329         if(ratio > p->basepri)
 330                 ratio = p->basepri;
 331         if(ratio < 0)
 332                 panic("reprioritize");
 333 //iprint("pid %d cpu %d load %d fair %d pri %d\n", p->pid, p->cpu, load, fairshare, ratio);
 334         return ratio;
 335 }
 336
 337 /*
 338  * add a process to a scheduling queue
 339  */
 340 void
 341 queueproc(Schedq *rq, Proc *p)
 342 {
 343         int pri;
 344
 345         pri = rq - runq;
 346         lock(runq);
 347         p->priority = pri;
 348         p->rnext = nil;
 349         if(rq->tail != nil)
 350                 rq->tail->rnext = p;
 351         else
 352                 rq->head = p;
 353         rq->tail = p;
 354         rq->n++;
 355         nrdy++;
 356         runvec |= 1<<pri;
 357         unlock(runq);
 358 }
 359
 360 /*
 361  *  try to remove a process from a scheduling queue (called splhi)
 362  */
 363 Proc*
 364 dequeueproc(Schedq *rq, Proc *tp)
 365 {
 366         Proc *l, *p;
 367
 368         if(!canlock(runq))
 369                 return nil;
 370
 371         /*
 372          *  the queue may have changed before we locked runq,
 373          *  refind the target process.
 374          */
 375         l = nil;
 376         for(p = rq->head; p != nil; p = p->rnext){
 377                 if(p == tp)
 378                         break;
 379                 l = p;
 380         }
 381
 382         /*
 383          *  p->mach==0 only when process state is saved
 384          */
 385         if(p == nil || p->mach != nil){
 386                 unlock(runq);
 387                 return nil;
 388         }
 389         if(p->rnext == nil)
 390                 rq->tail = l;
 391         if(l != nil)
 392                 l->rnext = p->rnext;
 393         else
 394                 rq->head = p->rnext;
 395         if(rq->head == nil)
 396                 runvec &= ~(1<<(rq-runq));
 397         rq->n--;
 398         nrdy--;
 399         if(p->state != Ready)
 400                 print("dequeueproc %s %lud %s\n", p->text, p->pid, statename[p->state]);
 401
 402         unlock(runq);
 403         return p;
 404 }
 405
 406 /*
 407  *  ready(p) picks a new priority for a process and sticks it in the
 408  *  runq for that priority.
 409  */
 410 void
 411 ready(Proc *p)
 412 {
 413         int s, pri;
 414         Schedq *rq;
 415         void (*pt)(Proc*, int, vlong);
 416
 417         if(p->state == Ready){
 418                 print("double ready %s %lud pc %p\n", p->text, p->pid, getcallerpc(&p));
 419                 return;
 420         }
 421
 422         s = splhi();
 423         if(edfready(p)){
 424                 splx(s);
 425                 return;
 426         }
 427
 428         if(up != p && (p->wired == nil || p->wired == MACHP(m->machno)))
 429                 m->readied = p; /* group scheduling */
 430
 431         updatecpu(p);
 432         pri = reprioritize(p);
 433         p->priority = pri;
 434         rq = &runq[pri];
 435         p->state = Ready;
 436         queueproc(rq, p);
 437         pt = proctrace;
 438         if(pt != nil)
 439                 pt(p, SReady, 0);
 440         splx(s);
 441 }
 442
 443 /*
 444  *  yield the processor and drop our priority
 445  */
 446 void
 447 yield(void)
 448 {
 449         if(anyready()){
 450                 /* pretend we just used 1/2 tick */
 451                 up->lastupdate -= Scaling/2;
 452                 sched();
 453         }
 454 }
 455
 456 /*
 457  *  recalculate priorities once a second.  We need to do this
 458  *  since priorities will otherwise only be recalculated when
 459  *  the running process blocks.
 460  */
 461 ulong balancetime;
 462
 463 static void
 464 rebalance(void)
 465 {
 466         int pri, npri, t, x;
 467         Schedq *rq;
 468         Proc *p;
 469
 470         t = m->ticks;
 471         if(t - balancetime < HZ)
 472                 return;
 473         balancetime = t;
 474
 475         for(pri=0, rq=runq; pri<Npriq; pri++, rq++){
 476 another:
 477                 p = rq->head;
 478                 if(p == nil)
 479                         continue;
 480                 if(p->mp != MACHP(m->machno))
 481                         continue;
 482                 if(pri == p->basepri)
 483                         continue;
 484                 updatecpu(p);
 485                 npri = reprioritize(p);
 486                 if(npri != pri){
 487                         x = splhi();
 488                         p = dequeueproc(rq, p);
 489                         if(p != nil)
 490                                 queueproc(&runq[npri], p);
 491                         splx(x);
 492                         goto another;
 493                 }
 494         }
 495 }
 496
 497
 498 /*
 499  *  pick a process to run
 500  */
 501 Proc*
 502 runproc(void)
 503 {
 504         Schedq *rq;
 505         Proc *p;
 506         ulong start, now;
 507         int i;
 508         void (*pt)(Proc*, int, vlong);
 509
 510         start = perfticks();
 511
 512         /* cooperative scheduling until the clock ticks */
 513         if((p = m->readied) != nil && p->mach == nil && p->state == Ready
 514         && (p->wired == nil || p->wired == MACHP(m->machno))
 515         && runq[Nrq-1].head == nil && runq[Nrq-2].head == nil){
 516                 skipscheds++;
 517                 rq = &runq[p->priority];
 518                 goto found;
 519         }
 520
 521         preempts++;
 522
 523 loop:
 524         /*
 525          *  find a process that last ran on this processor (affinity),
 526          *  or one that hasn't moved in a while (load balancing).  Every
 527          *  time around the loop affinity goes down.
 528          */
 529         spllo();
 530         for(i = 0;; i++){
 531                 /*
 532                  *  find the highest priority target process that this
 533                  *  processor can run given affinity constraints.
 534                  *
 535                  */
 536                 for(rq = &runq[Nrq-1]; rq >= runq; rq--){
 537                         for(p = rq->head; p != nil; p = p->rnext){
 538                                 if(p->mp == nil || p->mp == MACHP(m->machno)
 539                                 || (p->wired == nil && i > 0))
 540                                         goto found;
 541                         }
 542                 }
 543
 544                 /* waste time or halt the CPU */
 545                 idlehands();
 546
 547                 /* remember how much time we're here */
 548                 now = perfticks();
 549                 m->perf.inidle += now-start;
 550                 start = now;
 551         }
 552
 553 found:
 554         splhi();
 555         p = dequeueproc(rq, p);
 556         if(p == nil)
 557                 goto loop;
 558
 559         p->state = Scheding;
 560         p->mp = MACHP(m->machno);
 561
 562         if(edflock(p)){
 563                 edfrun(p, rq == &runq[PriEdf]); /* start deadline timer and do admin */
 564                 edfunlock();
 565         }
 566         pt = proctrace;
 567         if(pt != nil)
 568                 pt(p, SRun, 0);
 569         return p;
 570 }
 571
 572 int
 573 canpage(Proc *p)
 574 {
 575         int ok = 0;
 576
 577         splhi();
 578         lock(runq);
 579         /* Only reliable way to see if we are Running */
 580         if(p->mach == nil) {
 581                 p->newtlb = 1;
 582                 ok = 1;
 583         }
 584         unlock(runq);
 585         spllo();
 586
 587         return ok;
 588 }
 589
 590 Proc*
 591 newproc(void)
 592 {
 593         char msg[64];
 594         Proc *p;
 595
 596         lock(&procalloc);
 597         for(;;) {
 598                 if((p = procalloc.free) != nil)
 599                         break;
 600
 601                 snprint(msg, sizeof msg, "no procs; %s forking",
 602                         up != nil ? up->text: "kernel");
 603                 unlock(&procalloc);
 604                 resrcwait(msg);
 605                 lock(&procalloc);
 606         }
 607         procalloc.free = p->qnext;
 608         unlock(&procalloc);
 609
 610         p->state = Scheding;
 611         p->psstate = "New";
 612         p->mach = nil;
 613         p->eql = nil;
 614         p->qnext = nil;
 615         p->nchild = 0;
 616         p->nwait = 0;
 617         p->waitq = nil;
 618         p->parent = nil;
 619         p->pgrp = nil;
 620         p->egrp = nil;
 621         p->fgrp = nil;
 622         p->rgrp = nil;
 623         p->pdbg = nil;
 624         p->fpstate = FPinit;
 625         p->kp = 0;
 626         p->procctl = 0;
 627         p->syscalltrace = nil;
 628         p->notepending = 0;
 629         p->ureg = nil;
 630         p->privatemem = 0;
 631         p->noswap = 0;
 632         p->errstr = p->errbuf0;
 633         p->syserrstr = p->errbuf1;
 634         p->errbuf0[0] = '\0';
 635         p->errbuf1[0] = '\0';
 636         p->nlocks = 0;
 637         p->delaysched = 0;
 638         p->trace = 0;
 639         kstrdup(&p->user, "*nouser");
 640         kstrdup(&p->text, "*notext");
 641         kstrdup(&p->args, "");
 642         p->nargs = 0;
 643         p->setargs = 0;
 644         memset(p->seg, 0, sizeof p->seg);
 645         p->parentpid = 0;
 646         p->noteid = pidalloc(p);
 647         if(p->kstack == nil)
 648                 p->kstack = smalloc(KSTACK);
 649
 650         /* sched params */
 651         p->mp = nil;
 652         p->wired = nil;
 653         procpriority(p, PriNormal, 0);
 654         p->cpu = 0;
 655         p->lastupdate = MACHP(0)->ticks*Scaling;
 656         p->edf = nil;
 657
 658         return p;
 659 }
 660
 661 /*
 662  * wire this proc to a machine
 663  */
 664 void
 665 procwired(Proc *p, int bm)
 666 {
 667         Proc *pp;
 668         int i;
 669         char nwired[MAXMACH];
 670         Mach *wm;
 671
 672         if(bm < 0){
 673                 /* pick a machine to wire to */
 674                 memset(nwired, 0, sizeof(nwired));
 675                 p->wired = nil;
 676                 pp = proctab(0);
 677                 for(i=0; i<conf.nproc; i++, pp++){
 678                         wm = pp->wired;
 679                         if(wm != nil && pp->pid)
 680                                 nwired[wm->machno]++;
 681                 }
 682                 bm = 0;
 683                 for(i=0; i<conf.nmach; i++)
 684                         if(nwired[i] < nwired[bm])
 685                                 bm = i;
 686         } else {
 687                 /* use the virtual machine requested */
 688                 bm = bm % conf.nmach;
 689         }
 690
 691         p->wired = MACHP(bm);
 692         p->mp = p->wired;
 693 }
 694
 695 void
 696 procpriority(Proc *p, int pri, int fixed)
 697 {
 698         if(pri >= Npriq)
 699                 pri = Npriq - 1;
 700         else if(pri < 0)
 701                 pri = 0;
 702         p->basepri = pri;
 703         p->priority = pri;
 704         if(fixed){
 705                 p->fixedpri = 1;
 706         } else {
 707                 p->fixedpri = 0;
 708         }
 709 }
 710
 711 void
 712 procinit0(void)         /* bad planning - clashes with devproc.c */
 713 {
 714         Proc *p;
 715         int i;
 716
 717         p = xalloc(conf.nproc*sizeof(Proc));
 718         if(p == nil){
 719                 xsummary();
 720                 panic("cannot allocate %lud procs (%ludMB)", conf.nproc, conf.nproc*sizeof(Proc)/(1024*1024));
 721         }
 722         procalloc.arena = p;
 723         procalloc.free = p;
 724         for(i=0; i<conf.nproc-1; i++, p++)
 725                 p->qnext = p+1;
 726         p->qnext = nil;
 727 }
 728
 729 /*
 730  *  sleep if a condition is not true.  Another process will
 731  *  awaken us after it sets the condition.  When we awaken
 732  *  the condition may no longer be true.
 733  *
 734  *  we lock both the process and the rendezvous to keep r->p
 735  *  and p->r synchronized.
 736  */
 737 void
 738 sleep(Rendez *r, int (*f)(void*), void *arg)
 739 {
 740         int s;
 741         void (*pt)(Proc*, int, vlong);
 742
 743         s = splhi();
 744
 745         if(up->nlocks)
 746                 print("process %lud sleeps with %d locks held, last lock %#p locked at pc %#p, sleep called from %#p\n",
 747                         up->pid, up->nlocks, up->lastlock, up->lastlock->pc, getcallerpc(&r));
 748         lock(r);
 749         lock(&up->rlock);
 750         if(r->p != nil){
 751                 print("double sleep called from %#p, %lud %lud\n", getcallerpc(&r), r->p->pid, up->pid);
 752                 dumpstack();
 753         }
 754
 755         /*
 756          *  Wakeup only knows there may be something to do by testing
 757          *  r->p in order to get something to lock on.
 758          *  Flush that information out to memory in case the sleep is
 759          *  committed.
 760          */
 761         r->p = up;
 762
 763         if((*f)(arg) || up->notepending){
 764                 /*
 765                  *  if condition happened or a note is pending
 766                  *  never mind
 767                  */
 768                 r->p = nil;
 769                 unlock(&up->rlock);
 770                 unlock(r);
 771         } else {
 772                 /*
 773                  *  now we are committed to
 774                  *  change state and call scheduler
 775                  */
 776                 pt = proctrace;
 777                 if(pt != nil)
 778                         pt(up, SSleep, 0);
 779                 up->state = Wakeme;
 780                 up->r = r;
 781
 782                 /* statistics */
 783                 m->cs++;
 784
 785                 procsave(up);
 786                 if(setlabel(&up->sched)) {
 787                         /*
 788                          *  here when the process is awakened
 789                          */
 790                         procrestore(up);
 791                         spllo();
 792                 } else {
 793                         /*
 794                          *  here to go to sleep (i.e. stop Running)
 795                          */
 796                         unlock(&up->rlock);
 797                         unlock(r);
 798                         gotolabel(&m->sched);
 799                 }
 800         }
 801
 802         if(up->notepending) {
 803                 up->notepending = 0;
 804                 splx(s);
 805                 interrupted();
 806         }
 807
 808         splx(s);
 809 }
 810
 811 void
 812 interrupted(void)
 813 {
 814         if(up->procctl == Proc_exitme && up->closingfgrp != nil)
 815                 forceclosefgrp();
 816         error(Eintr);
 817 }
 818
 819 static int
 820 tfn(void *arg)
 821 {
 822         return up->trend == nil || up->tfn(arg);
 823 }
 824
 825 void
 826 twakeup(Ureg*, Timer *t)
 827 {
 828         Proc *p;
 829         Rendez *trend;
 830
 831         p = t->ta;
 832         trend = p->trend;
 833         p->trend = nil;
 834         if(trend != nil)
 835                 wakeup(trend);
 836 }
 837
 838 void
 839 tsleep(Rendez *r, int (*fn)(void*), void *arg, ulong ms)
 840 {
 841         if(up->tt != nil){
 842                 print("tsleep: timer active: mode %d, tf %#p\n", up->tmode, up->tf);
 843                 timerdel(up);
 844         }
 845         up->tns = MS2NS(ms);
 846         up->tf = twakeup;
 847         up->tmode = Trelative;
 848         up->ta = up;
 849         up->trend = r;
 850         up->tfn = fn;
 851         timeradd(up);
 852
 853         if(waserror()){
 854                 timerdel(up);
 855                 nexterror();
 856         }
 857         sleep(r, tfn, arg);
 858         if(up->tt != nil)
 859                 timerdel(up);
 860         up->twhen = 0;
 861         poperror();
 862 }
 863
 864 /*
 865  *  Expects that only one process can call wakeup for any given Rendez.
 866  *  We hold both locks to ensure that r->p and p->r remain consistent.
 867  *  Richard Miller has a better solution that doesn't require both to
 868  *  be held simultaneously, but I'm a paranoid - presotto.
 869  */
 870 Proc*
 871 wakeup(Rendez *r)
 872 {
 873         Proc *p;
 874         int s;
 875
 876         s = splhi();
 877
 878         lock(r);
 879         p = r->p;
 880
 881         if(p != nil){
 882                 lock(&p->rlock);
 883                 if(p->state != Wakeme || p->r != r){
 884                         iprint("%p %p %d\n", p->r, r, p->state);
 885                         panic("wakeup: state");
 886                 }
 887                 r->p = nil;
 888                 p->r = nil;
 889                 ready(p);
 890                 unlock(&p->rlock);
 891         }
 892         unlock(r);
 893
 894         splx(s);
 895
 896         return p;
 897 }
 898
 899 /*
 900  *  if waking a sleeping process, this routine must hold both
 901  *  p->rlock and r->lock.  However, it can't know them in
 902  *  the same order as wakeup causing a possible lock ordering
 903  *  deadlock.  We break the deadlock by giving up the p->rlock
 904  *  lock if we can't get the r->lock and retrying.
 905  */
 906 int
 907 postnote(Proc *p, int dolock, char *n, int flag)
 908 {
 909         int s, ret;
 910         QLock *q;
 911
 912         if(p == nil)
 913                 return 0;
 914
 915         if(dolock)
 916                 qlock(&p->debug);
 917
 918         if(p->pid == 0){
 919                 if(dolock)
 920                         qunlock(&p->debug);
 921                 return 0;
 922         }
 923
 924         if(n != nil && flag != NUser && (p->notify == 0 || p->notified))
 925                 p->nnote = 0;
 926
 927         ret = 0;
 928         if(p->nnote < NNOTE && n != nil) {
 929                 kstrcpy(p->note[p->nnote].msg, n, ERRMAX);
 930                 p->note[p->nnote++].flag = flag;
 931                 ret = 1;
 932         }
 933         p->notepending = 1;
 934         if(dolock)
 935                 qunlock(&p->debug);
 936
 937         /* this loop is to avoid lock ordering problems. */
 938         for(;;){
 939                 Rendez *r;
 940
 941                 s = splhi();
 942                 lock(&p->rlock);
 943                 r = p->r;
 944
 945                 /* waiting for a wakeup? */
 946                 if(r == nil)
 947                         break;  /* no */
 948
 949                 /* try for the second lock */
 950                 if(canlock(r)){
 951                         if(p->state != Wakeme || r->p != p)
 952                                 panic("postnote: state %d %d %d", r->p != p, p->r != r, p->state);
 953                         p->r = nil;
 954                         r->p = nil;
 955                         ready(p);
 956                         unlock(r);
 957                         break;
 958                 }
 959
 960                 /* give other process time to get out of critical section and try again */
 961                 unlock(&p->rlock);
 962                 splx(s);
 963                 sched();
 964         }
 965         unlock(&p->rlock);
 966         splx(s);
 967
 968         switch(p->state){
 969         case Queueing:
 970                 /* Try and pull out of a eqlock */
 971                 if((q = p->eql) != nil){
 972                         lock(&q->use);
 973                         if(p->state == Queueing && p->eql == q){
 974                                 Proc *d, *l;
 975
 976                                 for(l = nil, d = q->head; d != nil; l = d, d = d->qnext){
 977                                         if(d == p){
 978                                                 if(l != nil)
 979                                                         l->qnext = p->qnext;
 980                                                 else
 981                                                         q->head = p->qnext;
 982                                                 if(p->qnext == nil)
 983                                                         q->tail = l;
 984                                                 p->qnext = nil;
 985                                                 p->eql = nil;   /* not taken */
 986                                                 ready(p);
 987                                                 break;
 988                                         }
 989                                 }
 990                         }
 991                         unlock(&q->use);
 992                 }
 993                 break;
 994         case Rendezvous:
 995                 /* Try and pull out of a rendezvous */
 996                 lock(p->rgrp);
 997                 if(p->state == Rendezvous) {
 998                         Proc *d, **l;
 999
1000                         l = &REND(p->rgrp, p->rendtag);
1001                         for(d = *l; d != nil; d = d->rendhash) {
1002                                 if(d == p) {
1003                                         *l = p->rendhash;
1004                                         p->rendval = ~0;
1005                                         ready(p);
1006                                         break;
1007                                 }
1008                                 l = &d->rendhash;
1009                         }
1010                 }
1011                 unlock(p->rgrp);
1012                 break;
1013         }
1014         return ret;
1015 }
1016
1017 /*
1018  * weird thing: keep at most NBROKEN around
1019  */
1020 #define NBROKEN 4
1021 struct
1022 {
1023         QLock;
1024         int     n;
1025         Proc    *p[NBROKEN];
1026 }broken;
1027
1028 void
1029 addbroken(Proc *p)
1030 {
1031         qlock(&broken);
1032         if(broken.n == NBROKEN) {
1033                 ready(broken.p[0]);
1034                 memmove(&broken.p[0], &broken.p[1], sizeof(Proc*)*(NBROKEN-1));
1035                 --broken.n;
1036         }
1037         broken.p[broken.n++] = p;
1038         qunlock(&broken);
1039
1040         edfstop(up);
1041         p->state = Broken;
1042         p->psstate = nil;
1043         sched();
1044 }
1045
1046 void
1047 unbreak(Proc *p)
1048 {
1049         int b;
1050
1051         qlock(&broken);
1052         for(b=0; b < broken.n; b++)
1053                 if(broken.p[b] == p) {
1054                         broken.n--;
1055                         memmove(&broken.p[b], &broken.p[b+1],
1056                                         sizeof(Proc*)*(NBROKEN-(b+1)));
1057                         ready(p);
1058                         break;
1059                 }
1060         qunlock(&broken);
1061 }
1062
1063 int
1064 freebroken(void)
1065 {
1066         int i, n;
1067
1068         qlock(&broken);
1069         n = broken.n;
1070         for(i=0; i<n; i++) {
1071                 ready(broken.p[i]);
1072                 broken.p[i] = nil;
1073         }
1074         broken.n = 0;
1075         qunlock(&broken);
1076         return n;
1077 }
1078
1079 void
1080 pexit(char *exitstr, int freemem)
1081 {
1082         Proc *p;
1083         Segment **s, **es;
1084         long utime, stime;
1085         Waitq *wq;
1086         Fgrp *fgrp;
1087         Egrp *egrp;
1088         Rgrp *rgrp;
1089         Pgrp *pgrp;
1090         Chan *dot;
1091         void (*pt)(Proc*, int, vlong);
1092
1093         up->alarm = 0;
1094         if(up->tt != nil)
1095                 timerdel(up);
1096         pt = proctrace;
1097         if(pt != nil)
1098                 pt(up, SDead, 0);
1099
1100         /* nil out all the resources under lock (free later) */
1101         qlock(&up->debug);
1102         fgrp = up->fgrp;
1103         up->fgrp = nil;
1104         egrp = up->egrp;
1105         up->egrp = nil;
1106         rgrp = up->rgrp;
1107         up->rgrp = nil;
1108         pgrp = up->pgrp;
1109         up->pgrp = nil;
1110         dot = up->dot;
1111         up->dot = nil;
1112         qunlock(&up->debug);
1113
1114         if(fgrp != nil)
1115                 closefgrp(fgrp);
1116         if(egrp != nil)
1117                 closeegrp(egrp);
1118         if(rgrp != nil)
1119                 closergrp(rgrp);
1120         if(dot != nil)
1121                 cclose(dot);
1122         if(pgrp != nil)
1123                 closepgrp(pgrp);
1124
1125         /*
1126          * if not a kernel process and have a parent,
1127          * do some housekeeping.
1128          */
1129         if(up->kp == 0 && up->parentpid != 0) {
1130                 wq = smalloc(sizeof(Waitq));
1131                 wq->w.pid = up->pid;
1132                 utime = up->time[TUser] + up->time[TCUser];
1133                 stime = up->time[TSys] + up->time[TCSys];
1134                 wq->w.time[TUser] = tk2ms(utime);
1135                 wq->w.time[TSys] = tk2ms(stime);
1136                 wq->w.time[TReal] = tk2ms(MACHP(0)->ticks - up->time[TReal]);
1137                 if(exitstr != nil && exitstr[0])
1138                         snprint(wq->w.msg, sizeof(wq->w.msg), "%s %lud: %s", up->text, up->pid, exitstr);
1139                 else
1140                         wq->w.msg[0] = '\0';
1141
1142                 p = up->parent;
1143                 lock(&p->exl);
1144                 /*
1145                  * Check that parent is still alive.
1146                  */
1147                 if(p->pid == up->parentpid && p->state != Broken) {
1148                         p->nchild--;
1149                         p->time[TCUser] += utime;
1150                         p->time[TCSys] += stime;
1151                         /*
1152                          * If there would be more than 128 wait records
1153                          * processes for my parent, then don't leave a wait
1154                          * record behind.  This helps prevent badly written
1155                          * daemon processes from accumulating lots of wait
1156                          * records.
1157                          */
1158                         if(p->nwait < 128) {
1159                                 wq->next = p->waitq;
1160                                 p->waitq = wq;
1161                                 p->nwait++;
1162                                 wq = nil;
1163                                 wakeup(&p->waitr);
1164                         }
1165                 }
1166                 unlock(&p->exl);
1167                 if(wq != nil)
1168                         free(wq);
1169         }
1170         else if(up->kp == 0 && up->parent == nil){
1171                 if(exitstr == nil)
1172                         exitstr = "unknown";
1173                 panic("boot process died: %s", exitstr);
1174         }
1175
1176         if(!freemem)
1177                 addbroken(up);
1178
1179         qlock(&up->seglock);
1180         es = &up->seg[NSEG];
1181         for(s = up->seg; s < es; s++) {
1182                 if(*s != nil) {
1183                         putseg(*s);
1184                         *s = nil;
1185                 }
1186         }
1187         qunlock(&up->seglock);
1188
1189         lock(&up->exl);         /* Prevent my children from leaving waits */
1190         pidfree(up);
1191         up->pid = 0;
1192         wakeup(&up->waitr);
1193         unlock(&up->exl);
1194
1195         while((wq = up->waitq) != nil){
1196                 up->waitq = wq->next;
1197                 free(wq);
1198         }
1199
1200         /* release debuggers */
1201         qlock(&up->debug);
1202         if(up->pdbg != nil) {
1203                 wakeup(&up->pdbg->sleep);
1204                 up->pdbg = nil;
1205         }
1206         if(up->syscalltrace != nil) {
1207                 free(up->syscalltrace);
1208                 up->syscalltrace = nil;
1209         }
1210         qunlock(&up->debug);
1211
1212         /* Sched must not loop for these locks */
1213         lock(&procalloc);
1214         lock(&palloc);
1215
1216         edfstop(up);
1217         up->state = Moribund;
1218         sched();
1219         panic("pexit");
1220 }
1221
1222 static int
1223 haswaitq(void *x)
1224 {
1225         return ((Proc*)x)->waitq != nil;
1226 }
1227
1228 ulong
1229 pwait(Waitmsg *w)
1230 {
1231         ulong cpid;
1232         Waitq *wq;
1233
1234         if(!canqlock(&up->qwaitr))
1235                 error(Einuse);
1236
1237         if(waserror()) {
1238                 qunlock(&up->qwaitr);
1239                 nexterror();
1240         }
1241
1242         lock(&up->exl);
1243         while(up->waitq == nil) {
1244                 if(up->nchild == 0) {
1245                         unlock(&up->exl);
1246                         error(Enochild);
1247                 }
1248                 unlock(&up->exl);
1249                 sleep(&up->waitr, haswaitq, up);
1250                 lock(&up->exl);
1251         }
1252         wq = up->waitq;
1253         up->waitq = wq->next;
1254         up->nwait--;
1255         unlock(&up->exl);
1256
1257         qunlock(&up->qwaitr);
1258         poperror();
1259
1260         if(w != nil)
1261                 memmove(w, &wq->w, sizeof(Waitmsg));
1262         cpid = wq->w.pid;
1263         free(wq);
1264         return cpid;
1265 }
1266
1267 Proc*
1268 proctab(int i)
1269 {
1270         return &procalloc.arena[i];
1271 }
1272
1273 void
1274 dumpaproc(Proc *p)
1275 {
1276         ulong bss;
1277         char *s;
1278
1279         if(p == nil)
1280                 return;
1281
1282         bss = 0;
1283         if(p->seg[BSEG] != nil)
1284                 bss = p->seg[BSEG]->top;
1285
1286         s = p->psstate;
1287         if(s == nil)
1288                 s = statename[p->state];
1289         print("%3lud:%10s pc %#p dbgpc %#p  %8s (%s) ut %ld st %ld bss %lux qpc %#p nl %d nd %lud lpc %#p pri %lud\n",
1290                 p->pid, p->text, p->pc, dbgpc(p),  s, statename[p->state],
1291                 p->time[0], p->time[1], bss, p->qpc, p->nlocks, p->delaysched,
1292                 p->lastlock ? p->lastlock->pc : 0, p->priority);
1293 }
1294
1295 void
1296 procdump(void)
1297 {
1298         int i;
1299         Proc *p;
1300
1301         if(up != nil)
1302                 print("up %lud\n", up->pid);
1303         else
1304                 print("no current process\n");
1305         for(i=0; i<conf.nproc; i++) {
1306                 p = &procalloc.arena[i];
1307                 if(p->state != Dead)
1308                         dumpaproc(p);
1309         }
1310 }
1311
1312 /*
1313  *  wait till all processes have flushed their mmu
1314  *  state about segement s
1315  */
1316 void
1317 procflushseg(Segment *s)
1318 {
1319         int i, ns, nm, nwait;
1320         Proc *p;
1321
1322         /*
1323          *  tell all processes with this
1324          *  segment to flush their mmu's
1325          */
1326         nwait = 0;
1327         for(i=0; i<conf.nproc; i++) {
1328                 p = &procalloc.arena[i];
1329                 if(p->state == Dead)
1330                         continue;
1331                 for(ns = 0; ns < NSEG; ns++)
1332                         if(p->seg[ns] == s){
1333                                 p->newtlb = 1;
1334                                 for(nm = 0; nm < conf.nmach; nm++){
1335                                         if(MACHP(nm)->proc == p){
1336                                                 MACHP(nm)->flushmmu = 1;
1337                                                 nwait++;
1338                                         }
1339                                 }
1340                                 break;
1341                         }
1342         }
1343
1344         if(nwait == 0)
1345                 return;
1346
1347         /*
1348          *  wait for all other processors to take a clock interrupt
1349          *  and flush their mmu's
1350          */
1351         for(nm = 0; nm < conf.nmach; nm++)
1352                 while(m->machno != nm && MACHP(nm)->flushmmu)
1353                         sched();
1354 }
1355
1356 void
1357 scheddump(void)
1358 {
1359         Proc *p;
1360         Schedq *rq;
1361
1362         for(rq = &runq[Nrq-1]; rq >= runq; rq--){
1363                 if(rq->head == nil)
1364                         continue;
1365                 print("rq%ld:", rq-runq);
1366                 for(p = rq->head; p != nil; p = p->rnext)
1367                         print(" %lud(%lud)", p->pid, m->ticks - p->readytime);
1368                 print("\n");
1369                 delay(150);
1370         }
1371         print("nrdy %d\n", nrdy);
1372 }
1373
1374 void
1375 kproc(char *name, void (*func)(void *), void *arg)
1376 {
1377         Proc *p;
1378         static Pgrp *kpgrp;
1379
1380         p = newproc();
1381         p->psstate = nil;
1382         p->procmode = 0640;
1383         p->kp = 1;
1384         p->noswap = 1;
1385
1386         p->scallnr = up->scallnr;
1387         p->s = up->s;
1388         p->nerrlab = 0;
1389         p->slash = up->slash;
1390         p->dot = up->dot;
1391         if(p->dot != nil)
1392                 incref(p->dot);
1393
1394         memmove(p->note, up->note, sizeof(p->note));
1395         p->nnote = up->nnote;
1396         p->notified = 0;
1397         p->lastnote = up->lastnote;
1398         p->notify = up->notify;
1399         p->ureg = nil;
1400         p->dbgreg = nil;
1401
1402         procpriority(p, PriKproc, 0);
1403
1404         kprocchild(p, func, arg);
1405
1406         kstrdup(&p->user, eve);
1407         kstrdup(&p->text, name);
1408         if(kpgrp == nil)
1409                 kpgrp = newpgrp();
1410         p->pgrp = kpgrp;
1411         incref(kpgrp);
1412
1413         memset(p->time, 0, sizeof(p->time));
1414         p->time[TReal] = MACHP(0)->ticks;
1415         ready(p);
1416 }
1417
1418 /*
1419  *  called splhi() by notify().  See comment in notify for the
1420  *  reasoning.
1421  */
1422 void
1423 procctl(Proc *p)
1424 {
1425         char *state;
1426         ulong s;
1427
1428         switch(p->procctl) {
1429         case Proc_exitbig:
1430                 spllo();
1431                 pprint("Killed: Insufficient physical memory\n");
1432                 pexit("Killed: Insufficient physical memory", 1);
1433
1434         case Proc_exitme:
1435                 spllo();                /* pexit has locks in it */
1436                 pexit("Killed", 1);
1437
1438         case Proc_traceme:
1439                 if(p->nnote == 0)
1440                         return;
1441                 /* No break */
1442
1443         case Proc_stopme:
1444                 p->procctl = 0;
1445                 state = p->psstate;
1446                 p->psstate = "Stopped";
1447                 /* free a waiting debugger */
1448                 s = spllo();
1449                 qlock(&p->debug);
1450                 if(p->pdbg != nil) {
1451                         wakeup(&p->pdbg->sleep);
1452                         p->pdbg = nil;
1453                 }
1454                 qunlock(&p->debug);
1455                 splhi();
1456                 p->state = Stopped;
1457                 sched();
1458                 p->psstate = state;
1459                 splx(s);
1460                 return;
1461         }
1462 }
1463
1464 #include "errstr.h"
1465
1466 void
1467 error(char *err)
1468 {
1469         spllo();
1470
1471         assert(up->nerrlab < NERR);
1472         kstrcpy(up->errstr, err, ERRMAX);
1473         setlabel(&up->errlab[NERR-1]);
1474         nexterror();
1475 }
1476
1477 void
1478 nexterror(void)
1479 {
1480         assert(up->nerrlab > 0);
1481         gotolabel(&up->errlab[--up->nerrlab]);
1482 }
1483
1484 void
1485 exhausted(char *resource)
1486 {
1487         char buf[ERRMAX];
1488
1489         snprint(buf, sizeof buf, "no free %s", resource);
1490         iprint("%s\n", buf);
1491         error(buf);
1492 }
1493
1494 ulong
1495 procpagecount(Proc *p)
1496 {
1497         Segment *s;
1498         ulong pages;
1499         int i;
1500
1501         eqlock(&p->seglock);
1502         if(waserror()){
1503                 qunlock(&p->seglock);
1504                 nexterror();
1505         }
1506         pages = 0;
1507         for(i=0; i<NSEG; i++){
1508                 if((s = p->seg[i]) != nil){
1509                         eqlock(s);
1510                         pages += mcountseg(s);
1511                         qunlock(s);
1512                 }
1513         }
1514         qunlock(&p->seglock);
1515         poperror();
1516
1517         return pages;
1518 }
1519
1520 void
1521 killbig(char *why)
1522 {
1523         int i;
1524         Segment *s;
1525         ulong l, max;
1526         Proc *p, *ep, *kp;
1527
1528         max = 0;
1529         kp = nil;
1530         ep = procalloc.arena+conf.nproc;
1531         for(p = procalloc.arena; p < ep; p++) {
1532                 if(p->state == Dead || p->kp)
1533                         continue;
1534                 if((p->noswap || (p->procmode & 0222) == 0) && strcmp(eve, p->user) == 0)
1535                         continue;
1536                 l = procpagecount(p);
1537                 if(l > max){
1538                         kp = p;
1539                         max = l;
1540                 }
1541         }
1542         if(kp == nil)
1543                 return;
1544         print("%lud: %s killed: %s\n", kp->pid, kp->text, why);
1545         qlock(&kp->seglock);
1546         for(p = procalloc.arena; p < ep; p++) {
1547                 if(p->state == Dead || p->kp)
1548                         continue;
1549                 if(p != kp && p->seg[BSEG] != nil && p->seg[BSEG] == kp->seg[BSEG])
1550                         p->procctl = Proc_exitbig;
1551         }
1552         kp->procctl = Proc_exitbig;
1553         for(i = 0; i < NSEG; i++) {
1554                 s = kp->seg[i];
1555                 if(s != nil) {
1556                         qlock(s);
1557                         mfreeseg(s, s->base, (s->top - s->base)/BY2PG);
1558                         qunlock(s);
1559                 }
1560         }
1561         qunlock(&kp->seglock);
1562 }
1563
1564 /*
1565  *  change ownership to 'new' of all processes owned by 'old'.  Used when
1566  *  eve changes.
1567  */
1568 void
1569 renameuser(char *old, char *new)
1570 {
1571         Proc *p, *ep;
1572
1573         ep = procalloc.arena+conf.nproc;
1574         for(p = procalloc.arena; p < ep; p++)
1575                 if(p->user != nil && strcmp(old, p->user) == 0)
1576                         kstrdup(&p->user, new);
1577 }
1578
1579 /*
1580  *  time accounting called by clock() splhi'd
1581  */
1582 void
1583 accounttime(void)
1584 {
1585         Proc *p;
1586         ulong n, per;
1587         static ulong nrun;
1588
1589         p = m->proc;
1590         if(p != nil) {
1591                 nrun++;
1592                 p->time[p->insyscall]++;
1593         }
1594
1595         /* calculate decaying duty cycles */
1596         n = perfticks();
1597         per = n - m->perf.last;
1598         m->perf.last = n;
1599         per = (m->perf.period*(HZ-1) + per)/HZ;
1600         if(per != 0)
1601                 m->perf.period = per;
1602
1603         m->perf.avg_inidle = (m->perf.avg_inidle*(HZ-1)+m->perf.inidle)/HZ;
1604         m->perf.inidle = 0;
1605
1606         m->perf.avg_inintr = (m->perf.avg_inintr*(HZ-1)+m->perf.inintr)/HZ;
1607         m->perf.inintr = 0;
1608
1609         /* only one processor gets to compute system load averages */
1610         if(m->machno != 0)
1611                 return;
1612
1613         /*
1614          * calculate decaying load average.
1615          * if we decay by (n-1)/n then it takes
1616          * n clock ticks to go from load L to .36 L once
1617          * things quiet down.  it takes about 5 n clock
1618          * ticks to go to zero.  so using HZ means this is
1619          * approximately the load over the last second,
1620          * with a tail lasting about 5 seconds.
1621          */
1622         n = nrun;
1623         nrun = 0;
1624         n = (nrdy+n)*1000;
1625         m->load = (m->load*(HZ-1)+n)/HZ;
1626 }
1627
1628 int
1629 pidalloc(Proc *p)
1630 {
1631         static int gen, wrapped;
1632         int pid, h;
1633         Proc *x;
1634
1635         lock(&procalloc);
1636 Retry:
1637         pid = ++gen & 0x7FFFFFFF;
1638         if(pid == 0){
1639                 wrapped = 1;
1640                 goto Retry;
1641         }
1642         h = pid % nelem(procalloc.ht);
1643         if(wrapped)
1644                 for(x = procalloc.ht[h]; x != nil; x = x->pidhash)
1645                         if(x->pid == pid)
1646                                 goto Retry;
1647         if(p != nil){
1648                 p->pid = pid;
1649                 p->pidhash = procalloc.ht[h];
1650                 procalloc.ht[h] = p;
1651         }
1652         unlock(&procalloc);
1653         return pid;
1654 }
1655
1656 static void
1657 pidfree(Proc *p)
1658 {
1659         int h;
1660         Proc **l;
1661
1662         h = p->pid % nelem(procalloc.ht);
1663         lock(&procalloc);
1664         for(l = &procalloc.ht[h]; *l != nil; l = &(*l)->pidhash)
1665                 if(*l == p){
1666                         *l = p->pidhash;
1667                         break;
1668                 }
1669         unlock(&procalloc);
1670 }
1671
1672 int
1673 procindex(ulong pid)
1674 {
1675         Proc *p;
1676         int h;
1677         int s;
1678
1679         s = -1;
1680         h = pid % nelem(procalloc.ht);
1681         lock(&procalloc);
1682         for(p = procalloc.ht[h]; p != nil; p = p->pidhash)
1683                 if(p->pid == pid){
1684                         s = p - procalloc.arena;
1685                         break;
1686                 }
1687         unlock(&procalloc);
1688         return s;
1689 }