1 /*- 2 * Copyright (c) 1982, 1986, 1990, 1991, 1993 3 * The Regents of the University of California. All rights reserved. 4 * (c) UNIX System Laboratories, Inc. 5 * All or some portions of this file are derived from material licensed 6 * to the University of California by American Telephone and Telegraph 7 * Co. or Unix System Laboratories, Inc. and are reproduced herein with 8 * the permission of UNIX System Laboratories, Inc. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 * 38 * @(#)kern_synch.c 8.9 (Berkeley) 5/19/95 39 * $Id: kern_synch.c,v 1.31 1997/04/26 11:46:15 peter Exp $ 40 */ 41 42 #include "opt_ktrace.h" 43 #include "opt_smp.h" 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 #include <sys/proc.h> 48 #include <sys/kernel.h> 49 #include <sys/buf.h> 50 #include <sys/signalvar.h> 51 #include <sys/resourcevar.h> 52 #include <sys/signalvar.h> 53 #include <sys/vmmeter.h> 54 #include <vm/vm.h> 55 #include <vm/vm_param.h> 56 #include <vm/vm_extern.h> 57 #ifdef KTRACE 58 #include <sys/ktrace.h> 59 #endif 60 61 #include <machine/cpu.h> 62 63 static void rqinit __P((void *)); 64 SYSINIT(runqueue, SI_SUB_RUN_QUEUE, SI_ORDER_FIRST, rqinit, NULL) 65 66 u_char curpriority; /* usrpri of curproc */ 67 int lbolt; /* once a second sleep address */ 68 69 extern void endtsleep __P((void *)); 70 extern void updatepri __P((struct proc *p)); 71 72 /* 73 * Force switch among equal priority processes every 100ms. 74 */ 75 /* ARGSUSED */ 76 void 77 roundrobin(arg) 78 void *arg; 79 { 80 81 need_resched(); 82 timeout(roundrobin, NULL, hz / 10); 83 } 84 85 /* 86 * Constants for digital decay and forget: 87 * 90% of (p_estcpu) usage in 5 * loadav time 88 * 95% of (p_pctcpu) usage in 60 seconds (load insensitive) 89 * Note that, as ps(1) mentions, this can let percentages 90 * total over 100% (I've seen 137.9% for 3 processes). 91 * 92 * Note that statclock updates p_estcpu and p_cpticks independently. 93 * 94 * We wish to decay away 90% of p_estcpu in (5 * loadavg) seconds. 95 * That is, the system wants to compute a value of decay such 96 * that the following for loop: 97 * for (i = 0; i < (5 * loadavg); i++) 98 * p_estcpu *= decay; 99 * will compute 100 * p_estcpu *= 0.1; 101 * for all values of loadavg: 102 * 103 * Mathematically this loop can be expressed by saying: 104 * decay ** (5 * loadavg) ~= .1 105 * 106 * The system computes decay as: 107 * decay = (2 * loadavg) / (2 * loadavg + 1) 108 * 109 * We wish to prove that the system's computation of decay 110 * will always fulfill the equation: 111 * decay ** (5 * loadavg) ~= .1 112 * 113 * If we compute b as: 114 * b = 2 * loadavg 115 * then 116 * decay = b / (b + 1) 117 * 118 * We now need to prove two things: 119 * 1) Given factor ** (5 * loadavg) ~= .1, prove factor == b/(b+1) 120 * 2) Given b/(b+1) ** power ~= .1, prove power == (5 * loadavg) 121 * 122 * Facts: 123 * For x close to zero, exp(x) =~ 1 + x, since 124 * exp(x) = 0! + x**1/1! + x**2/2! + ... . 125 * therefore exp(-1/b) =~ 1 - (1/b) = (b-1)/b. 126 * For x close to zero, ln(1+x) =~ x, since 127 * ln(1+x) = x - x**2/2 + x**3/3 - ... -1 < x < 1 128 * therefore ln(b/(b+1)) = ln(1 - 1/(b+1)) =~ -1/(b+1). 129 * ln(.1) =~ -2.30 130 * 131 * Proof of (1): 132 * Solve (factor)**(power) =~ .1 given power (5*loadav): 133 * solving for factor, 134 * ln(factor) =~ (-2.30/5*loadav), or 135 * factor =~ exp(-1/((5/2.30)*loadav)) =~ exp(-1/(2*loadav)) = 136 * exp(-1/b) =~ (b-1)/b =~ b/(b+1). QED 137 * 138 * Proof of (2): 139 * Solve (factor)**(power) =~ .1 given factor == (b/(b+1)): 140 * solving for power, 141 * power*ln(b/(b+1)) =~ -2.30, or 142 * power =~ 2.3 * (b + 1) = 4.6*loadav + 2.3 =~ 5*loadav. QED 143 * 144 * Actual power values for the implemented algorithm are as follows: 145 * loadav: 1 2 3 4 146 * power: 5.68 10.32 14.94 19.55 147 */ 148 149 /* calculations for digital decay to forget 90% of usage in 5*loadav sec */ 150 #define loadfactor(loadav) (2 * (loadav)) 151 #define decay_cpu(loadfac, cpu) (((loadfac) * (cpu)) / ((loadfac) + FSCALE)) 152 153 /* decay 95% of `p_pctcpu' in 60 seconds; see CCPU_SHIFT before changing */ 154 fixpt_t ccpu = 0.95122942450071400909 * FSCALE; /* exp(-1/20) */ 155 156 /* 157 * If `ccpu' is not equal to `exp(-1/20)' and you still want to use the 158 * faster/more-accurate formula, you'll have to estimate CCPU_SHIFT below 159 * and possibly adjust FSHIFT in "param.h" so that (FSHIFT >= CCPU_SHIFT). 160 * 161 * To estimate CCPU_SHIFT for exp(-1/20), the following formula was used: 162 * 1 - exp(-1/20) ~= 0.0487 ~= 0.0488 == 1 (fixed pt, *11* bits). 163 * 164 * If you dont want to bother with the faster/more-accurate formula, you 165 * can set CCPU_SHIFT to (FSHIFT + 1) which will use a slower/less-accurate 166 * (more general) method of calculating the %age of CPU used by a process. 167 */ 168 #define CCPU_SHIFT 11 169 170 /* 171 * Recompute process priorities, every hz ticks. 172 */ 173 /* ARGSUSED */ 174 void 175 schedcpu(arg) 176 void *arg; 177 { 178 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 179 register struct proc *p; 180 register int s, i, j; 181 register unsigned int newcpu; 182 183 wakeup((caddr_t)&lbolt); 184 for (p = allproc.lh_first; p != 0; p = p->p_list.le_next) { 185 /* 186 * Increment time in/out of memory and sleep time 187 * (if sleeping). We ignore overflow; with 16-bit int's 188 * (remember them?) overflow takes 45 days. 189 */ 190 p->p_swtime++; 191 if (p->p_stat == SSLEEP || p->p_stat == SSTOP) 192 p->p_slptime++; 193 p->p_pctcpu = (p->p_pctcpu * ccpu) >> FSHIFT; 194 /* 195 * If the process has slept the entire second, 196 * stop recalculating its priority until it wakes up. 197 */ 198 if (p->p_slptime > 1) 199 continue; 200 s = splhigh(); /* prevent state changes and protect run queue */ 201 /* 202 * p_pctcpu is only for ps. 203 */ 204 #if (FSHIFT >= CCPU_SHIFT) 205 p->p_pctcpu += (hz == 100)? 206 ((fixpt_t) p->p_cpticks) << (FSHIFT - CCPU_SHIFT): 207 100 * (((fixpt_t) p->p_cpticks) 208 << (FSHIFT - CCPU_SHIFT)) / hz; 209 #else 210 p->p_pctcpu += ((FSCALE - ccpu) * 211 (p->p_cpticks * FSCALE / hz)) >> FSHIFT; 212 #endif 213 p->p_cpticks = 0; 214 newcpu = (u_int) decay_cpu(loadfac, p->p_estcpu) + p->p_nice; 215 p->p_estcpu = min(newcpu, UCHAR_MAX); 216 resetpriority(p); 217 if (p->p_priority >= PUSER) { 218 #define PPQ (128 / NQS) /* priorities per queue */ 219 if ((p != curproc) && 220 #ifdef SMP 221 (u_char)p->p_oncpu == 0xff && /* idle */ 222 #endif 223 p->p_stat == SRUN && 224 (p->p_flag & P_INMEM) && 225 (p->p_priority / PPQ) != (p->p_usrpri / PPQ)) { 226 remrq(p); 227 p->p_priority = p->p_usrpri; 228 setrunqueue(p); 229 } else 230 p->p_priority = p->p_usrpri; 231 } 232 splx(s); 233 not_mine: 234 } 235 vmmeter(); 236 timeout(schedcpu, (void *)0, hz); 237 } 238 239 /* 240 * Recalculate the priority of a process after it has slept for a while. 241 * For all load averages >= 1 and max p_estcpu of 255, sleeping for at 242 * least six times the loadfactor will decay p_estcpu to zero. 243 */ 244 void 245 updatepri(p) 246 register struct proc *p; 247 { 248 register unsigned int newcpu = p->p_estcpu; 249 register fixpt_t loadfac = loadfactor(averunnable.ldavg[0]); 250 251 if (p->p_slptime > 5 * loadfac) 252 p->p_estcpu = 0; 253 else { 254 p->p_slptime--; /* the first time was done in schedcpu */ 255 while (newcpu && --p->p_slptime) 256 newcpu = (int) decay_cpu(loadfac, newcpu); 257 p->p_estcpu = min(newcpu, UCHAR_MAX); 258 } 259 resetpriority(p); 260 } 261 262 /* 263 * We're only looking at 7 bits of the address; everything is 264 * aligned to 4, lots of things are aligned to greater powers 265 * of 2. Shift right by 8, i.e. drop the bottom 256 worth. 266 */ 267 #define TABLESIZE 128 268 TAILQ_HEAD(slpquehead, proc) slpque[TABLESIZE]; 269 #define LOOKUP(x) (((long)(x) >> 8) & (TABLESIZE - 1)) 270 271 /* 272 * During autoconfiguration or after a panic, a sleep will simply 273 * lower the priority briefly to allow interrupts, then return. 274 * The priority to be used (safepri) is machine-dependent, thus this 275 * value is initialized and maintained in the machine-dependent layers. 276 * This priority will typically be 0, or the lowest priority 277 * that is safe for use on the interrupt stack; it can be made 278 * higher to block network software interrupts after panics. 279 */ 280 int safepri; 281 282 void 283 sleepinit() 284 { 285 int i; 286 287 for (i = 0; i < TABLESIZE; i++) 288 TAILQ_INIT(&slpque[i]); 289 } 290 291 /* 292 * General sleep call. Suspends the current process until a wakeup is 293 * performed on the specified identifier. The process will then be made 294 * runnable with the specified priority. Sleeps at most timo/hz seconds 295 * (0 means no timeout). If pri includes PCATCH flag, signals are checked 296 * before and after sleeping, else signals are not checked. Returns 0 if 297 * awakened, EWOULDBLOCK if the timeout expires. If PCATCH is set and a 298 * signal needs to be delivered, ERESTART is returned if the current system 299 * call should be restarted if possible, and EINTR is returned if the system 300 * call should be interrupted by the signal (return EINTR). 301 */ 302 int 303 tsleep(ident, priority, wmesg, timo) 304 void *ident; 305 int priority, timo; 306 char *wmesg; 307 { 308 struct proc *p = curproc; 309 int s, sig, catch = priority & PCATCH; 310 311 #ifdef KTRACE 312 if (KTRPOINT(p, KTR_CSW)) 313 ktrcsw(p->p_tracep, 1, 0); 314 #endif 315 s = splhigh(); 316 if (cold || panicstr) { 317 /* 318 * After a panic, or during autoconfiguration, 319 * just give interrupts a chance, then just return; 320 * don't run any other procs or panic below, 321 * in case this is the idle process and already asleep. 322 */ 323 splx(safepri); 324 splx(s); 325 return (0); 326 } 327 #ifdef DIAGNOSTIC 328 if (ident == NULL || p->p_stat != SRUN) 329 panic("tsleep"); 330 #endif 331 p->p_wchan = ident; 332 p->p_wmesg = wmesg; 333 p->p_slptime = 0; 334 p->p_priority = priority & PRIMASK; 335 TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_procq); 336 if (timo) 337 timeout(endtsleep, (void *)p, timo); 338 /* 339 * We put ourselves on the sleep queue and start our timeout 340 * before calling CURSIG, as we could stop there, and a wakeup 341 * or a SIGCONT (or both) could occur while we were stopped. 342 * A SIGCONT would cause us to be marked as SSLEEP 343 * without resuming us, thus we must be ready for sleep 344 * when CURSIG is called. If the wakeup happens while we're 345 * stopped, p->p_wchan will be 0 upon return from CURSIG. 346 */ 347 if (catch) { 348 p->p_flag |= P_SINTR; 349 if ((sig = CURSIG(p))) { 350 if (p->p_wchan) 351 unsleep(p); 352 p->p_stat = SRUN; 353 goto resume; 354 } 355 if (p->p_wchan == 0) { 356 catch = 0; 357 goto resume; 358 } 359 } else 360 sig = 0; 361 p->p_stat = SSLEEP; 362 p->p_stats->p_ru.ru_nvcsw++; 363 mi_switch(); 364 resume: 365 curpriority = p->p_usrpri; 366 splx(s); 367 p->p_flag &= ~P_SINTR; 368 if (p->p_flag & P_TIMEOUT) { 369 p->p_flag &= ~P_TIMEOUT; 370 if (sig == 0) { 371 #ifdef KTRACE 372 if (KTRPOINT(p, KTR_CSW)) 373 ktrcsw(p->p_tracep, 0, 0); 374 #endif 375 return (EWOULDBLOCK); 376 } 377 } else if (timo) 378 untimeout(endtsleep, (void *)p); 379 if (catch && (sig != 0 || (sig = CURSIG(p)))) { 380 #ifdef KTRACE 381 if (KTRPOINT(p, KTR_CSW)) 382 ktrcsw(p->p_tracep, 0, 0); 383 #endif 384 if (p->p_sigacts->ps_sigintr & sigmask(sig)) 385 return (EINTR); 386 return (ERESTART); 387 } 388 #ifdef KTRACE 389 if (KTRPOINT(p, KTR_CSW)) 390 ktrcsw(p->p_tracep, 0, 0); 391 #endif 392 return (0); 393 } 394 395 /* 396 * Implement timeout for tsleep. 397 * If process hasn't been awakened (wchan non-zero), 398 * set timeout flag and undo the sleep. If proc 399 * is stopped, just unsleep so it will remain stopped. 400 */ 401 void 402 endtsleep(arg) 403 void *arg; 404 { 405 register struct proc *p; 406 int s; 407 408 p = (struct proc *)arg; 409 s = splhigh(); 410 if (p->p_wchan) { 411 if (p->p_stat == SSLEEP) 412 setrunnable(p); 413 else 414 unsleep(p); 415 p->p_flag |= P_TIMEOUT; 416 } 417 splx(s); 418 } 419 420 /* 421 * Remove a process from its wait queue 422 */ 423 void 424 unsleep(p) 425 register struct proc *p; 426 { 427 int s; 428 429 s = splhigh(); 430 if (p->p_wchan) { 431 TAILQ_REMOVE(&slpque[LOOKUP(p->p_wchan)], p, p_procq); 432 p->p_wchan = 0; 433 } 434 splx(s); 435 } 436 437 /* 438 * Make all processes sleeping on the specified identifier runnable. 439 */ 440 void 441 wakeup(ident) 442 register void *ident; 443 { 444 register struct slpquehead *qp; 445 register struct proc *p; 446 int s; 447 448 s = splhigh(); 449 qp = &slpque[LOOKUP(ident)]; 450 restart: 451 for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) { 452 #ifdef DIAGNOSTIC 453 if (p->p_stat != SSLEEP && p->p_stat != SSTOP) 454 panic("wakeup"); 455 #endif 456 if (p->p_wchan == ident) { 457 TAILQ_REMOVE(qp, p, p_procq); 458 p->p_wchan = 0; 459 if (p->p_stat == SSLEEP) { 460 /* OPTIMIZED EXPANSION OF setrunnable(p); */ 461 if (p->p_slptime > 1) 462 updatepri(p); 463 p->p_slptime = 0; 464 p->p_stat = SRUN; 465 if (p->p_flag & P_INMEM) { 466 setrunqueue(p); 467 need_resched(); 468 } else { 469 p->p_flag |= P_SWAPINREQ; 470 wakeup((caddr_t)&proc0); 471 } 472 /* END INLINE EXPANSION */ 473 goto restart; 474 } 475 } 476 } 477 splx(s); 478 } 479 480 /* 481 * Make a process sleeping on the specified identifier runnable. 482 * May wake more than one process if a target prcoess is currently 483 * swapped out. 484 */ 485 void 486 wakeup_one(ident) 487 register void *ident; 488 { 489 register struct slpquehead *qp; 490 register struct proc *p; 491 int s; 492 493 s = splhigh(); 494 qp = &slpque[LOOKUP(ident)]; 495 496 for (p = qp->tqh_first; p != NULL; p = p->p_procq.tqe_next) { 497 #ifdef DIAGNOSTIC 498 if (p->p_stat != SSLEEP && p->p_stat != SSTOP) 499 panic("wakeup_one"); 500 #endif 501 if (p->p_wchan == ident) { 502 TAILQ_REMOVE(qp, p, p_procq); 503 p->p_wchan = 0; 504 if (p->p_stat == SSLEEP) { 505 /* OPTIMIZED EXPANSION OF setrunnable(p); */ 506 if (p->p_slptime > 1) 507 updatepri(p); 508 p->p_slptime = 0; 509 p->p_stat = SRUN; 510 if (p->p_flag & P_INMEM) { 511 setrunqueue(p); 512 need_resched(); 513 break; 514 } else { 515 p->p_flag |= P_SWAPINREQ; 516 wakeup((caddr_t)&proc0); 517 } 518 /* END INLINE EXPANSION */ 519 } 520 } 521 } 522 splx(s); 523 } 524 525 /* 526 * The machine independent parts of mi_switch(). 527 * Must be called at splstatclock() or higher. 528 */ 529 void 530 mi_switch() 531 { 532 register struct proc *p = curproc; /* XXX */ 533 register struct rlimit *rlim; 534 register long s, u; 535 int x; 536 struct timeval tv; 537 538 /* 539 * XXX this spl is almost unnecessary. It is partly to allow for 540 * sloppy callers that don't do it (issignal() via CURSIG() is the 541 * main offender). It is partly to work around a bug in the i386 542 * cpu_switch() (the ipl is not preserved). We ran for years 543 * without it. I think there was only a interrupt latency problem. 544 * The main caller, tsleep(), does an splx() a couple of instructions 545 * after calling here. The buggy caller, issignal(), usually calls 546 * here at spl0() and sometimes returns at splhigh(). The process 547 * then runs for a little too long at splhigh(). The ipl gets fixed 548 * when the process returns to user mode (or earlier). 549 * 550 * It would probably be better to always call here at spl0(). Callers 551 * are prepared to give up control to another process, so they must 552 * be prepared to be interrupted. The clock stuff here may not 553 * actually need splstatclock(). 554 */ 555 x = splstatclock(); 556 557 #ifdef SIMPLELOCK_DEBUG 558 if (p->p_simple_locks) 559 printf("sleep: holding simple lock"); 560 #endif 561 /* 562 * Compute the amount of time during which the current 563 * process was running, and add that to its total so far. 564 */ 565 microtime(&tv); 566 u = p->p_rtime.tv_usec + (tv.tv_usec - runtime.tv_usec); 567 s = p->p_rtime.tv_sec + (tv.tv_sec - runtime.tv_sec); 568 if (u < 0) { 569 u += 1000000; 570 s--; 571 } else if (u >= 1000000) { 572 u -= 1000000; 573 s++; 574 } 575 #ifdef SMP 576 if (s < 0) 577 s = u = 0; 578 #endif 579 p->p_rtime.tv_usec = u; 580 p->p_rtime.tv_sec = s; 581 582 /* 583 * Check if the process exceeds its cpu resource allocation. 584 * If over max, kill it. 585 */ 586 if (p->p_stat != SZOMB) { 587 rlim = &p->p_rlimit[RLIMIT_CPU]; 588 if (s >= rlim->rlim_cur) { 589 if (s >= rlim->rlim_max) 590 killproc(p, "exceeded maximum CPU limit"); 591 else { 592 psignal(p, SIGXCPU); 593 if (rlim->rlim_cur < rlim->rlim_max) 594 rlim->rlim_cur += 5; 595 } 596 } 597 } 598 599 /* 600 * Pick a new current process and record its start time. 601 */ 602 cnt.v_swtch++; 603 cpu_switch(p); 604 microtime(&runtime); 605 splx(x); 606 } 607 608 /* 609 * Initialize the (doubly-linked) run queues 610 * to be empty. 611 */ 612 /* ARGSUSED*/ 613 static void 614 rqinit(dummy) 615 void *dummy; 616 { 617 register int i; 618 619 for (i = 0; i < NQS; i++) { 620 qs[i].ph_link = qs[i].ph_rlink = (struct proc *)&qs[i]; 621 rtqs[i].ph_link = rtqs[i].ph_rlink = (struct proc *)&rtqs[i]; 622 idqs[i].ph_link = idqs[i].ph_rlink = (struct proc *)&idqs[i]; 623 } 624 } 625 626 /* 627 * Change process state to be runnable, 628 * placing it on the run queue if it is in memory, 629 * and awakening the swapper if it isn't in memory. 630 */ 631 void 632 setrunnable(p) 633 register struct proc *p; 634 { 635 register int s; 636 637 s = splhigh(); 638 switch (p->p_stat) { 639 case 0: 640 case SRUN: 641 case SZOMB: 642 default: 643 panic("setrunnable"); 644 case SSTOP: 645 case SSLEEP: 646 unsleep(p); /* e.g. when sending signals */ 647 break; 648 649 case SIDL: 650 break; 651 } 652 p->p_stat = SRUN; 653 if (p->p_flag & P_INMEM) 654 setrunqueue(p); 655 splx(s); 656 if (p->p_slptime > 1) 657 updatepri(p); 658 p->p_slptime = 0; 659 if ((p->p_flag & P_INMEM) == 0) { 660 p->p_flag |= P_SWAPINREQ; 661 wakeup((caddr_t)&proc0); 662 } 663 else if (p->p_priority < curpriority) 664 need_resched(); 665 } 666 667 /* 668 * Compute the priority of a process when running in user mode. 669 * Arrange to reschedule if the resulting priority is better 670 * than that of the current process. 671 */ 672 void 673 resetpriority(p) 674 register struct proc *p; 675 { 676 register unsigned int newpriority; 677 678 if (p->p_rtprio.type == RTP_PRIO_NORMAL) { 679 newpriority = PUSER + p->p_estcpu / 4 + 2 * p->p_nice; 680 newpriority = min(newpriority, MAXPRI); 681 p->p_usrpri = newpriority; 682 if (newpriority < curpriority) 683 need_resched(); 684 } else { 685 need_resched(); 686 } 687 } 688