OSDN Git Service

runtime: Ignore stack sizes when deciding when to GC.
[pf3gnuchains/gcc-fork.git] / libgo / runtime / proc.c
1 // Copyright 2009 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
4
5 #include <limits.h>
6 #include <stdlib.h>
7 #include <pthread.h>
8 #include <unistd.h>
9
10 #include "config.h"
11 #include "runtime.h"
12 #include "arch.h"
13 #include "defs.h"
14 #include "malloc.h"
15 #include "go-defer.h"
16
17 #ifdef USING_SPLIT_STACK
18
19 /* FIXME: These are not declared anywhere.  */
20
21 extern void __splitstack_getcontext(void *context[10]);
22
23 extern void __splitstack_setcontext(void *context[10]);
24
25 extern void *__splitstack_makecontext(size_t, void *context[10], size_t *);
26
27 extern void * __splitstack_resetcontext(void *context[10], size_t *);
28
29 extern void *__splitstack_find(void *, void *, size_t *, void **, void **,
30                                void **);
31
32 extern void __splitstack_block_signals (int *, int *);
33
34 extern void __splitstack_block_signals_context (void *context[10], int *,
35                                                 int *);
36
37 #endif
38
39 #if defined(USING_SPLIT_STACK) && defined(LINKER_SUPPORTS_SPLIT_STACK)
40 # ifdef PTHREAD_STACK_MIN
41 #  define StackMin PTHREAD_STACK_MIN
42 # else
43 #  define StackMin 8192
44 # endif
45 #else
46 # define StackMin 2 * 1024 * 1024
47 #endif
48
49 uintptr runtime_stacks_sys;
50
51 static void schedule(G*);
52
53 typedef struct Sched Sched;
54
55 M       runtime_m0;
56 G       runtime_g0;     // idle goroutine for m0
57
58 #ifdef __rtems__
59 #define __thread
60 #endif
61
62 static __thread G *g;
63 static __thread M *m;
64
65 #ifndef SETCONTEXT_CLOBBERS_TLS
66
67 static inline void
68 initcontext(void)
69 {
70 }
71
72 static inline void
73 fixcontext(ucontext_t *c __attribute__ ((unused)))
74 {
75 }
76
77 # else
78
79 # if defined(__x86_64__) && defined(__sun__)
80
81 // x86_64 Solaris 10 and 11 have a bug: setcontext switches the %fs
82 // register to that of the thread which called getcontext.  The effect
83 // is that the address of all __thread variables changes.  This bug
84 // also affects pthread_self() and pthread_getspecific.  We work
85 // around it by clobbering the context field directly to keep %fs the
86 // same.
87
88 static __thread greg_t fs;
89
90 static inline void
91 initcontext(void)
92 {
93         ucontext_t c;
94
95         getcontext(&c);
96         fs = c.uc_mcontext.gregs[REG_FSBASE];
97 }
98
99 static inline void
100 fixcontext(ucontext_t* c)
101 {
102         c->uc_mcontext.gregs[REG_FSBASE] = fs;
103 }
104
105 # else
106
107 #  error unknown case for SETCONTEXT_CLOBBERS_TLS
108
109 # endif
110
111 #endif
112
113 // We can not always refer to the TLS variables directly.  The
114 // compiler will call tls_get_addr to get the address of the variable,
115 // and it may hold it in a register across a call to schedule.  When
116 // we get back from the call we may be running in a different thread,
117 // in which case the register now points to the TLS variable for a
118 // different thread.  We use non-inlinable functions to avoid this
119 // when necessary.
120
121 G* runtime_g(void) __attribute__ ((noinline, no_split_stack));
122
123 G*
124 runtime_g(void)
125 {
126         return g;
127 }
128
129 M* runtime_m(void) __attribute__ ((noinline, no_split_stack));
130
131 M*
132 runtime_m(void)
133 {
134         return m;
135 }
136
137 int32   runtime_gcwaiting;
138
139 // Go scheduler
140 //
141 // The go scheduler's job is to match ready-to-run goroutines (`g's)
142 // with waiting-for-work schedulers (`m's).  If there are ready g's
143 // and no waiting m's, ready() will start a new m running in a new
144 // OS thread, so that all ready g's can run simultaneously, up to a limit.
145 // For now, m's never go away.
146 //
147 // By default, Go keeps only one kernel thread (m) running user code
148 // at a single time; other threads may be blocked in the operating system.
149 // Setting the environment variable $GOMAXPROCS or calling
150 // runtime.GOMAXPROCS() will change the number of user threads
151 // allowed to execute simultaneously.  $GOMAXPROCS is thus an
152 // approximation of the maximum number of cores to use.
153 //
154 // Even a program that can run without deadlock in a single process
155 // might use more m's if given the chance.  For example, the prime
156 // sieve will use as many m's as there are primes (up to runtime_sched.mmax),
157 // allowing different stages of the pipeline to execute in parallel.
158 // We could revisit this choice, only kicking off new m's for blocking
159 // system calls, but that would limit the amount of parallel computation
160 // that go would try to do.
161 //
162 // In general, one could imagine all sorts of refinements to the
163 // scheduler, but the goal now is just to get something working on
164 // Linux and OS X.
165
166 struct Sched {
167         Lock;
168
169         G *gfree;       // available g's (status == Gdead)
170         int32 goidgen;
171
172         G *ghead;       // g's waiting to run
173         G *gtail;
174         int32 gwait;    // number of g's waiting to run
175         int32 gcount;   // number of g's that are alive
176         int32 grunning; // number of g's running on cpu or in syscall
177
178         M *mhead;       // m's waiting for work
179         int32 mwait;    // number of m's waiting for work
180         int32 mcount;   // number of m's that have been created
181
182         volatile uint32 atomic; // atomic scheduling word (see below)
183
184         int32 profilehz;        // cpu profiling rate
185
186         bool init;  // running initialization
187         bool lockmain;  // init called runtime.LockOSThread
188
189         Note    stopped;        // one g can set waitstop and wait here for m's to stop
190 };
191
192 // The atomic word in sched is an atomic uint32 that
193 // holds these fields.
194 //
195 //      [15 bits] mcpu          number of m's executing on cpu
196 //      [15 bits] mcpumax       max number of m's allowed on cpu
197 //      [1 bit] waitstop        some g is waiting on stopped
198 //      [1 bit] gwaiting        gwait != 0
199 //
200 // These fields are the information needed by entersyscall
201 // and exitsyscall to decide whether to coordinate with the
202 // scheduler.  Packing them into a single machine word lets
203 // them use a fast path with a single atomic read/write and
204 // no lock/unlock.  This greatly reduces contention in
205 // syscall- or cgo-heavy multithreaded programs.
206 //
207 // Except for entersyscall and exitsyscall, the manipulations
208 // to these fields only happen while holding the schedlock,
209 // so the routines holding schedlock only need to worry about
210 // what entersyscall and exitsyscall do, not the other routines
211 // (which also use the schedlock).
212 //
213 // In particular, entersyscall and exitsyscall only read mcpumax,
214 // waitstop, and gwaiting.  They never write them.  Thus, writes to those
215 // fields can be done (holding schedlock) without fear of write conflicts.
216 // There may still be logic conflicts: for example, the set of waitstop must
217 // be conditioned on mcpu >= mcpumax or else the wait may be a
218 // spurious sleep.  The Promela model in proc.p verifies these accesses.
219 enum {
220         mcpuWidth = 15,
221         mcpuMask = (1<<mcpuWidth) - 1,
222         mcpuShift = 0,
223         mcpumaxShift = mcpuShift + mcpuWidth,
224         waitstopShift = mcpumaxShift + mcpuWidth,
225         gwaitingShift = waitstopShift+1,
226
227         // The max value of GOMAXPROCS is constrained
228         // by the max value we can store in the bit fields
229         // of the atomic word.  Reserve a few high values
230         // so that we can detect accidental decrement
231         // beyond zero.
232         maxgomaxprocs = mcpuMask - 10,
233 };
234
235 #define atomic_mcpu(v)          (((v)>>mcpuShift)&mcpuMask)
236 #define atomic_mcpumax(v)       (((v)>>mcpumaxShift)&mcpuMask)
237 #define atomic_waitstop(v)      (((v)>>waitstopShift)&1)
238 #define atomic_gwaiting(v)      (((v)>>gwaitingShift)&1)
239
240 Sched runtime_sched;
241 int32 runtime_gomaxprocs;
242 bool runtime_singleproc;
243
244 static bool canaddmcpu(void);
245
246 // An m that is waiting for notewakeup(&m->havenextg).  This may
247 // only be accessed while the scheduler lock is held.  This is used to
248 // minimize the number of times we call notewakeup while the scheduler
249 // lock is held, since the m will normally move quickly to lock the
250 // scheduler itself, producing lock contention.
251 static M* mwakeup;
252
253 // Scheduling helpers.  Sched must be locked.
254 static void gput(G*);   // put/get on ghead/gtail
255 static G* gget(void);
256 static void mput(M*);   // put/get on mhead
257 static M* mget(G*);
258 static void gfput(G*);  // put/get on gfree
259 static G* gfget(void);
260 static void matchmg(void);      // match m's to g's
261 static void readylocked(G*);    // ready, but sched is locked
262 static void mnextg(M*, G*);
263 static void mcommoninit(M*);
264
265 void
266 setmcpumax(uint32 n)
267 {
268         uint32 v, w;
269
270         for(;;) {
271                 v = runtime_sched.atomic;
272                 w = v;
273                 w &= ~(mcpuMask<<mcpumaxShift);
274                 w |= n<<mcpumaxShift;
275                 if(runtime_cas(&runtime_sched.atomic, v, w))
276                         break;
277         }
278 }
279
280 // First function run by a new goroutine.  This replaces gogocall.
281 static void
282 kickoff(void)
283 {
284         void (*fn)(void*);
285
286         fn = (void (*)(void*))(g->entry);
287         fn(g->param);
288         runtime_goexit();
289 }
290
291 // Switch context to a different goroutine.  This is like longjmp.
292 static void runtime_gogo(G*) __attribute__ ((noinline));
293 static void
294 runtime_gogo(G* newg)
295 {
296 #ifdef USING_SPLIT_STACK
297         __splitstack_setcontext(&newg->stack_context[0]);
298 #endif
299         g = newg;
300         newg->fromgogo = true;
301         fixcontext(&newg->context);
302         setcontext(&newg->context);
303         runtime_throw("gogo setcontext returned");
304 }
305
306 // Save context and call fn passing g as a parameter.  This is like
307 // setjmp.  Because getcontext always returns 0, unlike setjmp, we use
308 // g->fromgogo as a code.  It will be true if we got here via
309 // setcontext.  g == nil the first time this is called in a new m.
310 static void runtime_mcall(void (*)(G*)) __attribute__ ((noinline));
311 static void
312 runtime_mcall(void (*pfn)(G*))
313 {
314         M *mp;
315         G *gp;
316 #ifndef USING_SPLIT_STACK
317         int i;
318 #endif
319
320         // Ensure that all registers are on the stack for the garbage
321         // collector.
322         __builtin_unwind_init();
323
324         mp = m;
325         gp = g;
326         if(gp == mp->g0)
327                 runtime_throw("runtime: mcall called on m->g0 stack");
328
329         if(gp != nil) {
330
331 #ifdef USING_SPLIT_STACK
332                 __splitstack_getcontext(&g->stack_context[0]);
333 #else
334                 gp->gcnext_sp = &i;
335 #endif
336                 gp->fromgogo = false;
337                 getcontext(&gp->context);
338
339                 // When we return from getcontext, we may be running
340                 // in a new thread.  That means that m and g may have
341                 // changed.  They are global variables so we will
342                 // reload them, but the addresses of m and g may be
343                 // cached in our local stack frame, and those
344                 // addresses may be wrong.  Call functions to reload
345                 // the values for this thread.
346                 mp = runtime_m();
347                 gp = runtime_g();
348         }
349         if (gp == nil || !gp->fromgogo) {
350 #ifdef USING_SPLIT_STACK
351                 __splitstack_setcontext(&mp->g0->stack_context[0]);
352 #endif
353                 mp->g0->entry = (byte*)pfn;
354                 mp->g0->param = gp;
355
356                 // It's OK to set g directly here because this case
357                 // can not occur if we got here via a setcontext to
358                 // the getcontext call just above.
359                 g = mp->g0;
360
361                 fixcontext(&mp->g0->context);
362                 setcontext(&mp->g0->context);
363                 runtime_throw("runtime: mcall function returned");
364         }
365 }
366
367 // Keep trace of scavenger's goroutine for deadlock detection.
368 static G *scvg;
369
370 // The bootstrap sequence is:
371 //
372 //      call osinit
373 //      call schedinit
374 //      make & queue new G
375 //      call runtime_mstart
376 //
377 // The new G calls runtime_main.
378 void
379 runtime_schedinit(void)
380 {
381         int32 n;
382         const byte *p;
383
384         m = &runtime_m0;
385         g = &runtime_g0;
386         m->g0 = g;
387         m->curg = g;
388         g->m = m;
389
390         initcontext();
391
392         m->nomemprof++;
393         runtime_mallocinit();
394         mcommoninit(m);
395
396         runtime_goargs();
397         runtime_goenvs();
398
399         // For debugging:
400         // Allocate internal symbol table representation now,
401         // so that we don't need to call malloc when we crash.
402         // runtime_findfunc(0);
403
404         runtime_gomaxprocs = 1;
405         p = runtime_getenv("GOMAXPROCS");
406         if(p != nil && (n = runtime_atoi(p)) != 0) {
407                 if(n > maxgomaxprocs)
408                         n = maxgomaxprocs;
409                 runtime_gomaxprocs = n;
410         }
411         // wait for the main goroutine to start before taking
412         // GOMAXPROCS into account.
413         setmcpumax(1);
414         runtime_singleproc = runtime_gomaxprocs == 1;
415
416         canaddmcpu();   // mcpu++ to account for bootstrap m
417         m->helpgc = 1;  // flag to tell schedule() to mcpu--
418         runtime_sched.grunning++;
419
420         // Can not enable GC until all roots are registered.
421         // mstats.enablegc = 1;
422         m->nomemprof--;
423 }
424
425 extern void main_init(void) __asm__ ("__go_init_main");
426 extern void main_main(void) __asm__ ("main.main");
427
428 // The main goroutine.
429 void
430 runtime_main(void)
431 {
432         // Lock the main goroutine onto this, the main OS thread,
433         // during initialization.  Most programs won't care, but a few
434         // do require certain calls to be made by the main thread.
435         // Those can arrange for main.main to run in the main thread
436         // by calling runtime.LockOSThread during initialization
437         // to preserve the lock.
438         runtime_LockOSThread();
439         // From now on, newgoroutines may use non-main threads.
440         setmcpumax(runtime_gomaxprocs);
441         runtime_sched.init = true;
442         scvg = __go_go(runtime_MHeap_Scavenger, nil);
443         main_init();
444         runtime_sched.init = false;
445         if(!runtime_sched.lockmain)
446                 runtime_UnlockOSThread();
447
448         // For gccgo we have to wait until after main is initialized
449         // to enable GC, because initializing main registers the GC
450         // roots.
451         mstats.enablegc = 1;
452
453         // The deadlock detection has false negatives.
454         // Let scvg start up, to eliminate the false negative
455         // for the trivial program func main() { select{} }.
456         runtime_gosched();
457
458         main_main();
459         runtime_exit(0);
460         for(;;)
461                 *(int32*)0 = 0;
462 }
463
464 // Lock the scheduler.
465 static void
466 schedlock(void)
467 {
468         runtime_lock(&runtime_sched);
469 }
470
471 // Unlock the scheduler.
472 static void
473 schedunlock(void)
474 {
475         M *m;
476
477         m = mwakeup;
478         mwakeup = nil;
479         runtime_unlock(&runtime_sched);
480         if(m != nil)
481                 runtime_notewakeup(&m->havenextg);
482 }
483
484 void
485 runtime_goexit(void)
486 {
487         g->status = Gmoribund;
488         runtime_gosched();
489 }
490
491 void
492 runtime_goroutineheader(G *g)
493 {
494         const char *status;
495
496         switch(g->status) {
497         case Gidle:
498                 status = "idle";
499                 break;
500         case Grunnable:
501                 status = "runnable";
502                 break;
503         case Grunning:
504                 status = "running";
505                 break;
506         case Gsyscall:
507                 status = "syscall";
508                 break;
509         case Gwaiting:
510                 if(g->waitreason)
511                         status = g->waitreason;
512                 else
513                         status = "waiting";
514                 break;
515         case Gmoribund:
516                 status = "moribund";
517                 break;
518         default:
519                 status = "???";
520                 break;
521         }
522         runtime_printf("goroutine %d [%s]:\n", g->goid, status);
523 }
524
525 void
526 runtime_tracebackothers(G *me)
527 {
528         G *g;
529
530         for(g = runtime_allg; g != nil; g = g->alllink) {
531                 if(g == me || g->status == Gdead)
532                         continue;
533                 runtime_printf("\n");
534                 runtime_goroutineheader(g);
535                 // runtime_traceback(g->sched.pc, g->sched.sp, 0, g);
536         }
537 }
538
539 // Mark this g as m's idle goroutine.
540 // This functionality might be used in environments where programs
541 // are limited to a single thread, to simulate a select-driven
542 // network server.  It is not exposed via the standard runtime API.
543 void
544 runtime_idlegoroutine(void)
545 {
546         if(g->idlem != nil)
547                 runtime_throw("g is already an idle goroutine");
548         g->idlem = m;
549 }
550
551 static void
552 mcommoninit(M *m)
553 {
554         m->id = runtime_sched.mcount++;
555         m->fastrand = 0x49f6428aUL + m->id + runtime_cputicks();
556
557         if(m->mcache == nil)
558                 m->mcache = runtime_allocmcache();
559
560         runtime_callers(1, m->createstack, nelem(m->createstack));
561
562         // Add to runtime_allm so garbage collector doesn't free m
563         // when it is just in a register or thread-local storage.
564         m->alllink = runtime_allm;
565         // runtime_NumCgoCall() iterates over allm w/o schedlock,
566         // so we need to publish it safely.
567         runtime_atomicstorep(&runtime_allm, m);
568 }
569
570 // Try to increment mcpu.  Report whether succeeded.
571 static bool
572 canaddmcpu(void)
573 {
574         uint32 v;
575
576         for(;;) {
577                 v = runtime_sched.atomic;
578                 if(atomic_mcpu(v) >= atomic_mcpumax(v))
579                         return 0;
580                 if(runtime_cas(&runtime_sched.atomic, v, v+(1<<mcpuShift)))
581                         return 1;
582         }
583 }
584
585 // Put on `g' queue.  Sched must be locked.
586 static void
587 gput(G *g)
588 {
589         M *m;
590
591         // If g is wired, hand it off directly.
592         if((m = g->lockedm) != nil && canaddmcpu()) {
593                 mnextg(m, g);
594                 return;
595         }
596
597         // If g is the idle goroutine for an m, hand it off.
598         if(g->idlem != nil) {
599                 if(g->idlem->idleg != nil) {
600                         runtime_printf("m%d idle out of sync: g%d g%d\n",
601                                 g->idlem->id,
602                                 g->idlem->idleg->goid, g->goid);
603                         runtime_throw("runtime: double idle");
604                 }
605                 g->idlem->idleg = g;
606                 return;
607         }
608
609         g->schedlink = nil;
610         if(runtime_sched.ghead == nil)
611                 runtime_sched.ghead = g;
612         else
613                 runtime_sched.gtail->schedlink = g;
614         runtime_sched.gtail = g;
615
616         // increment gwait.
617         // if it transitions to nonzero, set atomic gwaiting bit.
618         if(runtime_sched.gwait++ == 0)
619                 runtime_xadd(&runtime_sched.atomic, 1<<gwaitingShift);
620 }
621
622 // Report whether gget would return something.
623 static bool
624 haveg(void)
625 {
626         return runtime_sched.ghead != nil || m->idleg != nil;
627 }
628
629 // Get from `g' queue.  Sched must be locked.
630 static G*
631 gget(void)
632 {
633         G *g;
634
635         g = runtime_sched.ghead;
636         if(g){
637                 runtime_sched.ghead = g->schedlink;
638                 if(runtime_sched.ghead == nil)
639                         runtime_sched.gtail = nil;
640                 // decrement gwait.
641                 // if it transitions to zero, clear atomic gwaiting bit.
642                 if(--runtime_sched.gwait == 0)
643                         runtime_xadd(&runtime_sched.atomic, -1<<gwaitingShift);
644         } else if(m->idleg != nil) {
645                 g = m->idleg;
646                 m->idleg = nil;
647         }
648         return g;
649 }
650
651 // Put on `m' list.  Sched must be locked.
652 static void
653 mput(M *m)
654 {
655         m->schedlink = runtime_sched.mhead;
656         runtime_sched.mhead = m;
657         runtime_sched.mwait++;
658 }
659
660 // Get an `m' to run `g'.  Sched must be locked.
661 static M*
662 mget(G *g)
663 {
664         M *m;
665
666         // if g has its own m, use it.
667         if(g && (m = g->lockedm) != nil)
668                 return m;
669
670         // otherwise use general m pool.
671         if((m = runtime_sched.mhead) != nil){
672                 runtime_sched.mhead = m->schedlink;
673                 runtime_sched.mwait--;
674         }
675         return m;
676 }
677
678 // Mark g ready to run.
679 void
680 runtime_ready(G *g)
681 {
682         schedlock();
683         readylocked(g);
684         schedunlock();
685 }
686
687 // Mark g ready to run.  Sched is already locked.
688 // G might be running already and about to stop.
689 // The sched lock protects g->status from changing underfoot.
690 static void
691 readylocked(G *g)
692 {
693         if(g->m){
694                 // Running on another machine.
695                 // Ready it when it stops.
696                 g->readyonstop = 1;
697                 return;
698         }
699
700         // Mark runnable.
701         if(g->status == Grunnable || g->status == Grunning) {
702                 runtime_printf("goroutine %d has status %d\n", g->goid, g->status);
703                 runtime_throw("bad g->status in ready");
704         }
705         g->status = Grunnable;
706
707         gput(g);
708         matchmg();
709 }
710
711 // Same as readylocked but a different symbol so that
712 // debuggers can set a breakpoint here and catch all
713 // new goroutines.
714 static void
715 newprocreadylocked(G *g)
716 {
717         readylocked(g);
718 }
719
720 // Pass g to m for running.
721 // Caller has already incremented mcpu.
722 static void
723 mnextg(M *m, G *g)
724 {
725         runtime_sched.grunning++;
726         m->nextg = g;
727         if(m->waitnextg) {
728                 m->waitnextg = 0;
729                 if(mwakeup != nil)
730                         runtime_notewakeup(&mwakeup->havenextg);
731                 mwakeup = m;
732         }
733 }
734
735 // Get the next goroutine that m should run.
736 // Sched must be locked on entry, is unlocked on exit.
737 // Makes sure that at most $GOMAXPROCS g's are
738 // running on cpus (not in system calls) at any given time.
739 static G*
740 nextgandunlock(void)
741 {
742         G *gp;
743         uint32 v;
744
745 top:
746         if(atomic_mcpu(runtime_sched.atomic) >= maxgomaxprocs)
747                 runtime_throw("negative mcpu");
748
749         // If there is a g waiting as m->nextg, the mcpu++
750         // happened before it was passed to mnextg.
751         if(m->nextg != nil) {
752                 gp = m->nextg;
753                 m->nextg = nil;
754                 schedunlock();
755                 return gp;
756         }
757
758         if(m->lockedg != nil) {
759                 // We can only run one g, and it's not available.
760                 // Make sure some other cpu is running to handle
761                 // the ordinary run queue.
762                 if(runtime_sched.gwait != 0) {
763                         matchmg();
764                         // m->lockedg might have been on the queue.
765                         if(m->nextg != nil) {
766                                 gp = m->nextg;
767                                 m->nextg = nil;
768                                 schedunlock();
769                                 return gp;
770                         }
771                 }
772         } else {
773                 // Look for work on global queue.
774                 while(haveg() && canaddmcpu()) {
775                         gp = gget();
776                         if(gp == nil)
777                                 runtime_throw("gget inconsistency");
778
779                         if(gp->lockedm) {
780                                 mnextg(gp->lockedm, gp);
781                                 continue;
782                         }
783                         runtime_sched.grunning++;
784                         schedunlock();
785                         return gp;
786                 }
787
788                 // The while loop ended either because the g queue is empty
789                 // or because we have maxed out our m procs running go
790                 // code (mcpu >= mcpumax).  We need to check that
791                 // concurrent actions by entersyscall/exitsyscall cannot
792                 // invalidate the decision to end the loop.
793                 //
794                 // We hold the sched lock, so no one else is manipulating the
795                 // g queue or changing mcpumax.  Entersyscall can decrement
796                 // mcpu, but if does so when there is something on the g queue,
797                 // the gwait bit will be set, so entersyscall will take the slow path
798                 // and use the sched lock.  So it cannot invalidate our decision.
799                 //
800                 // Wait on global m queue.
801                 mput(m);
802         }
803
804         // Look for deadlock situation.
805         // There is a race with the scavenger that causes false negatives:
806         // if the scavenger is just starting, then we have
807         //      scvg != nil && grunning == 0 && gwait == 0
808         // and we do not detect a deadlock.  It is possible that we should
809         // add that case to the if statement here, but it is too close to Go 1
810         // to make such a subtle change.  Instead, we work around the
811         // false negative in trivial programs by calling runtime.gosched
812         // from the main goroutine just before main.main.
813         // See runtime_main above.
814         //
815         // On a related note, it is also possible that the scvg == nil case is
816         // wrong and should include gwait, but that does not happen in
817         // standard Go programs, which all start the scavenger.
818         //
819         if((scvg == nil && runtime_sched.grunning == 0) ||
820            (scvg != nil && runtime_sched.grunning == 1 && runtime_sched.gwait == 0 &&
821             (scvg->status == Grunning || scvg->status == Gsyscall))) {
822                 runtime_throw("all goroutines are asleep - deadlock!");
823         }
824
825         m->nextg = nil;
826         m->waitnextg = 1;
827         runtime_noteclear(&m->havenextg);
828
829         // Stoptheworld is waiting for all but its cpu to go to stop.
830         // Entersyscall might have decremented mcpu too, but if so
831         // it will see the waitstop and take the slow path.
832         // Exitsyscall never increments mcpu beyond mcpumax.
833         v = runtime_atomicload(&runtime_sched.atomic);
834         if(atomic_waitstop(v) && atomic_mcpu(v) <= atomic_mcpumax(v)) {
835                 // set waitstop = 0 (known to be 1)
836                 runtime_xadd(&runtime_sched.atomic, -1<<waitstopShift);
837                 runtime_notewakeup(&runtime_sched.stopped);
838         }
839         schedunlock();
840
841         runtime_notesleep(&m->havenextg);
842         if(m->helpgc) {
843                 runtime_gchelper();
844                 m->helpgc = 0;
845                 runtime_lock(&runtime_sched);
846                 goto top;
847         }
848         if((gp = m->nextg) == nil)
849                 runtime_throw("bad m->nextg in nextgoroutine");
850         m->nextg = nil;
851         return gp;
852 }
853
854 int32
855 runtime_helpgc(bool *extra)
856 {
857         M *mp;
858         int32 n, max;
859
860         // Figure out how many CPUs to use.
861         // Limited by gomaxprocs, number of actual CPUs, and MaxGcproc.
862         max = runtime_gomaxprocs;
863         if(max > runtime_ncpu)
864                 max = runtime_ncpu > 0 ? runtime_ncpu : 1;
865         if(max > MaxGcproc)
866                 max = MaxGcproc;
867
868         // We're going to use one CPU no matter what.
869         // Figure out the max number of additional CPUs.
870         max--;
871
872         runtime_lock(&runtime_sched);
873         n = 0;
874         while(n < max && (mp = mget(nil)) != nil) {
875                 n++;
876                 mp->helpgc = 1;
877                 mp->waitnextg = 0;
878                 runtime_notewakeup(&mp->havenextg);
879         }
880         runtime_unlock(&runtime_sched);
881         if(extra)
882                 *extra = n != max;
883         return n;
884 }
885
886 void
887 runtime_stoptheworld(void)
888 {
889         uint32 v;
890
891         schedlock();
892         runtime_gcwaiting = 1;
893
894         setmcpumax(1);
895
896         // while mcpu > 1
897         for(;;) {
898                 v = runtime_sched.atomic;
899                 if(atomic_mcpu(v) <= 1)
900                         break;
901
902                 // It would be unsafe for multiple threads to be using
903                 // the stopped note at once, but there is only
904                 // ever one thread doing garbage collection.
905                 runtime_noteclear(&runtime_sched.stopped);
906                 if(atomic_waitstop(v))
907                         runtime_throw("invalid waitstop");
908
909                 // atomic { waitstop = 1 }, predicated on mcpu <= 1 check above
910                 // still being true.
911                 if(!runtime_cas(&runtime_sched.atomic, v, v+(1<<waitstopShift)))
912                         continue;
913
914                 schedunlock();
915                 runtime_notesleep(&runtime_sched.stopped);
916                 schedlock();
917         }
918         runtime_singleproc = runtime_gomaxprocs == 1;
919         schedunlock();
920 }
921
922 void
923 runtime_starttheworld(bool extra)
924 {
925         M *m;
926
927         schedlock();
928         runtime_gcwaiting = 0;
929         setmcpumax(runtime_gomaxprocs);
930         matchmg();
931         if(extra && canaddmcpu()) {
932                 // Start a new m that will (we hope) be idle
933                 // and so available to help when the next
934                 // garbage collection happens.
935                 // canaddmcpu above did mcpu++
936                 // (necessary, because m will be doing various
937                 // initialization work so is definitely running),
938                 // but m is not running a specific goroutine,
939                 // so set the helpgc flag as a signal to m's
940                 // first schedule(nil) to mcpu-- and grunning--.
941                 m = runtime_newm();
942                 m->helpgc = 1;
943                 runtime_sched.grunning++;
944         }
945         schedunlock();
946 }
947
948 // Called to start an M.
949 void*
950 runtime_mstart(void* mp)
951 {
952         m = (M*)mp;
953         g = m->g0;
954
955         initcontext();
956
957         g->entry = nil;
958         g->param = nil;
959
960         // Record top of stack for use by mcall.
961         // Once we call schedule we're never coming back,
962         // so other calls can reuse this stack space.
963 #ifdef USING_SPLIT_STACK
964         __splitstack_getcontext(&g->stack_context[0]);
965 #else
966         g->gcinitial_sp = &mp;
967         // Setting gcstack_size to 0 is a marker meaning that gcinitial_sp
968         // is the top of the stack, not the bottom.
969         g->gcstack_size = 0;
970         g->gcnext_sp = &mp;
971 #endif
972         getcontext(&g->context);
973
974         if(g->entry != nil) {
975                 // Got here from mcall.
976                 void (*pfn)(G*) = (void (*)(G*))g->entry;
977                 G* gp = (G*)g->param;
978                 pfn(gp);
979                 *(int*)0x21 = 0x21;
980         }
981         runtime_minit();
982
983 #ifdef USING_SPLIT_STACK
984         {
985           int dont_block_signals = 0;
986           __splitstack_block_signals(&dont_block_signals, nil);
987         }
988 #endif
989
990         // Install signal handlers; after minit so that minit can
991         // prepare the thread to be able to handle the signals.
992         if(m == &runtime_m0)
993                 runtime_initsig();
994
995         schedule(nil);
996         return nil;
997 }
998
999 typedef struct CgoThreadStart CgoThreadStart;
1000 struct CgoThreadStart
1001 {
1002         M *m;
1003         G *g;
1004         void (*fn)(void);
1005 };
1006
1007 // Kick off new m's as needed (up to mcpumax).
1008 // Sched is locked.
1009 static void
1010 matchmg(void)
1011 {
1012         G *gp;
1013         M *mp;
1014
1015         if(m->mallocing || m->gcing)
1016                 return;
1017
1018         while(haveg() && canaddmcpu()) {
1019                 gp = gget();
1020                 if(gp == nil)
1021                         runtime_throw("gget inconsistency");
1022
1023                 // Find the m that will run gp.
1024                 if((mp = mget(gp)) == nil)
1025                         mp = runtime_newm();
1026                 mnextg(mp, gp);
1027         }
1028 }
1029
1030 // Create a new m.  It will start off with a call to runtime_mstart.
1031 M*
1032 runtime_newm(void)
1033 {
1034         M *m;
1035         pthread_attr_t attr;
1036         pthread_t tid;
1037
1038         m = runtime_malloc(sizeof(M));
1039         mcommoninit(m);
1040         m->g0 = runtime_malg(-1, nil, nil);
1041
1042         if(pthread_attr_init(&attr) != 0)
1043                 runtime_throw("pthread_attr_init");
1044         if(pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED) != 0)
1045                 runtime_throw("pthread_attr_setdetachstate");
1046
1047 #ifndef PTHREAD_STACK_MIN
1048 #define PTHREAD_STACK_MIN 8192
1049 #endif
1050         if(pthread_attr_setstacksize(&attr, PTHREAD_STACK_MIN) != 0)
1051                 runtime_throw("pthread_attr_setstacksize");
1052
1053         if(pthread_create(&tid, &attr, runtime_mstart, m) != 0)
1054                 runtime_throw("pthread_create");
1055
1056         return m;
1057 }
1058
1059 // One round of scheduler: find a goroutine and run it.
1060 // The argument is the goroutine that was running before
1061 // schedule was called, or nil if this is the first call.
1062 // Never returns.
1063 static void
1064 schedule(G *gp)
1065 {
1066         int32 hz;
1067         uint32 v;
1068
1069         schedlock();
1070         if(gp != nil) {
1071                 // Just finished running gp.
1072                 gp->m = nil;
1073                 runtime_sched.grunning--;
1074
1075                 // atomic { mcpu-- }
1076                 v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
1077                 if(atomic_mcpu(v) > maxgomaxprocs)
1078                         runtime_throw("negative mcpu in scheduler");
1079
1080                 switch(gp->status){
1081                 case Grunnable:
1082                 case Gdead:
1083                         // Shouldn't have been running!
1084                         runtime_throw("bad gp->status in sched");
1085                 case Grunning:
1086                         gp->status = Grunnable;
1087                         gput(gp);
1088                         break;
1089                 case Gmoribund:
1090                         gp->status = Gdead;
1091                         if(gp->lockedm) {
1092                                 gp->lockedm = nil;
1093                                 m->lockedg = nil;
1094                         }
1095                         gp->idlem = nil;
1096                         runtime_memclr(&gp->context, sizeof gp->context);
1097                         gfput(gp);
1098                         if(--runtime_sched.gcount == 0)
1099                                 runtime_exit(0);
1100                         break;
1101                 }
1102                 if(gp->readyonstop){
1103                         gp->readyonstop = 0;
1104                         readylocked(gp);
1105                 }
1106         } else if(m->helpgc) {
1107                 // Bootstrap m or new m started by starttheworld.
1108                 // atomic { mcpu-- }
1109                 v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
1110                 if(atomic_mcpu(v) > maxgomaxprocs)
1111                         runtime_throw("negative mcpu in scheduler");
1112                 // Compensate for increment in starttheworld().
1113                 runtime_sched.grunning--;
1114                 m->helpgc = 0;
1115         } else if(m->nextg != nil) {
1116                 // New m started by matchmg.
1117         } else {
1118                 runtime_throw("invalid m state in scheduler");
1119         }
1120
1121         // Find (or wait for) g to run.  Unlocks runtime_sched.
1122         gp = nextgandunlock();
1123         gp->readyonstop = 0;
1124         gp->status = Grunning;
1125         m->curg = gp;
1126         gp->m = m;
1127
1128         // Check whether the profiler needs to be turned on or off.
1129         hz = runtime_sched.profilehz;
1130         if(m->profilehz != hz)
1131                 runtime_resetcpuprofiler(hz);
1132
1133         runtime_gogo(gp);
1134 }
1135
1136 // Enter scheduler.  If g->status is Grunning,
1137 // re-queues g and runs everyone else who is waiting
1138 // before running g again.  If g->status is Gmoribund,
1139 // kills off g.
1140 void
1141 runtime_gosched(void)
1142 {
1143         if(m->locks != 0)
1144                 runtime_throw("gosched holding locks");
1145         if(g == m->g0)
1146                 runtime_throw("gosched of g0");
1147         runtime_mcall(schedule);
1148 }
1149
1150 // The goroutine g is about to enter a system call.
1151 // Record that it's not using the cpu anymore.
1152 // This is called only from the go syscall library and cgocall,
1153 // not from the low-level system calls used by the runtime.
1154 //
1155 // Entersyscall cannot split the stack: the runtime_gosave must
1156 // make g->sched refer to the caller's stack segment, because
1157 // entersyscall is going to return immediately after.
1158 // It's okay to call matchmg and notewakeup even after
1159 // decrementing mcpu, because we haven't released the
1160 // sched lock yet, so the garbage collector cannot be running.
1161
1162 void runtime_entersyscall(void) __attribute__ ((no_split_stack));
1163
1164 void
1165 runtime_entersyscall(void)
1166 {
1167         uint32 v;
1168
1169         if(m->profilehz > 0)
1170                 runtime_setprof(false);
1171
1172         // Leave SP around for gc and traceback.
1173 #ifdef USING_SPLIT_STACK
1174         g->gcstack = __splitstack_find(NULL, NULL, &g->gcstack_size,
1175                                        &g->gcnext_segment, &g->gcnext_sp,
1176                                        &g->gcinitial_sp);
1177 #else
1178         g->gcnext_sp = (byte *) &v;
1179 #endif
1180
1181         // Save the registers in the g structure so that any pointers
1182         // held in registers will be seen by the garbage collector.
1183         // We could use getcontext here, but setjmp is more efficient
1184         // because it doesn't need to save the signal mask.
1185         setjmp(g->gcregs);
1186
1187         g->status = Gsyscall;
1188
1189         // Fast path.
1190         // The slow path inside the schedlock/schedunlock will get
1191         // through without stopping if it does:
1192         //      mcpu--
1193         //      gwait not true
1194         //      waitstop && mcpu <= mcpumax not true
1195         // If we can do the same with a single atomic add,
1196         // then we can skip the locks.
1197         v = runtime_xadd(&runtime_sched.atomic, -1<<mcpuShift);
1198         if(!atomic_gwaiting(v) && (!atomic_waitstop(v) || atomic_mcpu(v) > atomic_mcpumax(v)))
1199                 return;
1200
1201         schedlock();
1202         v = runtime_atomicload(&runtime_sched.atomic);
1203         if(atomic_gwaiting(v)) {
1204                 matchmg();
1205                 v = runtime_atomicload(&runtime_sched.atomic);
1206         }
1207         if(atomic_waitstop(v) && atomic_mcpu(v) <= atomic_mcpumax(v)) {
1208                 runtime_xadd(&runtime_sched.atomic, -1<<waitstopShift);
1209                 runtime_notewakeup(&runtime_sched.stopped);
1210         }
1211
1212         schedunlock();
1213 }
1214
1215 // The goroutine g exited its system call.
1216 // Arrange for it to run on a cpu again.
1217 // This is called only from the go syscall library, not
1218 // from the low-level system calls used by the runtime.
1219 void
1220 runtime_exitsyscall(void)
1221 {
1222         G *gp;
1223         uint32 v;
1224
1225         // Fast path.
1226         // If we can do the mcpu++ bookkeeping and
1227         // find that we still have mcpu <= mcpumax, then we can
1228         // start executing Go code immediately, without having to
1229         // schedlock/schedunlock.
1230         gp = g;
1231         v = runtime_xadd(&runtime_sched.atomic, (1<<mcpuShift));
1232         if(m->profilehz == runtime_sched.profilehz && atomic_mcpu(v) <= atomic_mcpumax(v)) {
1233                 // There's a cpu for us, so we can run.
1234                 gp->status = Grunning;
1235                 // Garbage collector isn't running (since we are),
1236                 // so okay to clear gcstack.
1237 #ifdef USING_SPLIT_STACK
1238                 gp->gcstack = nil;
1239 #endif
1240                 gp->gcnext_sp = nil;
1241                 runtime_memclr(gp->gcregs, sizeof gp->gcregs);
1242
1243                 if(m->profilehz > 0)
1244                         runtime_setprof(true);
1245                 return;
1246         }
1247
1248         // Tell scheduler to put g back on the run queue:
1249         // mostly equivalent to g->status = Grunning,
1250         // but keeps the garbage collector from thinking
1251         // that g is running right now, which it's not.
1252         gp->readyonstop = 1;
1253
1254         // All the cpus are taken.
1255         // The scheduler will ready g and put this m to sleep.
1256         // When the scheduler takes g away from m,
1257         // it will undo the runtime_sched.mcpu++ above.
1258         runtime_gosched();
1259
1260         // Gosched returned, so we're allowed to run now.
1261         // Delete the gcstack information that we left for
1262         // the garbage collector during the system call.
1263         // Must wait until now because until gosched returns
1264         // we don't know for sure that the garbage collector
1265         // is not running.
1266 #ifdef USING_SPLIT_STACK
1267         gp->gcstack = nil;
1268 #endif
1269         gp->gcnext_sp = nil;
1270         runtime_memclr(gp->gcregs, sizeof gp->gcregs);
1271 }
1272
1273 // Allocate a new g, with a stack big enough for stacksize bytes.
1274 G*
1275 runtime_malg(int32 stacksize, byte** ret_stack, size_t* ret_stacksize)
1276 {
1277         G *newg;
1278
1279         newg = runtime_malloc(sizeof(G));
1280         if(stacksize >= 0) {
1281 #if USING_SPLIT_STACK
1282                 int dont_block_signals = 0;
1283
1284                 *ret_stack = __splitstack_makecontext(stacksize,
1285                                                       &newg->stack_context[0],
1286                                                       ret_stacksize);
1287                 __splitstack_block_signals_context(&newg->stack_context[0],
1288                                                    &dont_block_signals, nil);
1289 #else
1290                 *ret_stack = runtime_mallocgc(stacksize, FlagNoProfiling|FlagNoGC, 0, 0);
1291                 *ret_stacksize = stacksize;
1292                 newg->gcinitial_sp = *ret_stack;
1293                 newg->gcstack_size = stacksize;
1294                 runtime_xadd(&runtime_stacks_sys, stacksize);
1295 #endif
1296         }
1297         return newg;
1298 }
1299
1300 /* For runtime package testing.  */
1301
1302 void runtime_testing_entersyscall(void)
1303   __asm__("libgo_runtime.runtime.entersyscall");
1304
1305 void
1306 runtime_testing_entersyscall()
1307 {
1308         runtime_entersyscall();
1309 }
1310
1311 void runtime_testing_exitsyscall(void)
1312   __asm__("libgo_runtime.runtime.exitsyscall");
1313
1314 void
1315 runtime_testing_exitsyscall()
1316 {
1317         runtime_exitsyscall();
1318 }
1319
1320 G*
1321 __go_go(void (*fn)(void*), void* arg)
1322 {
1323         byte *sp;
1324         size_t spsize;
1325         G * volatile newg;      // volatile to avoid longjmp warning
1326
1327         schedlock();
1328
1329         if((newg = gfget()) != nil){
1330 #ifdef USING_SPLIT_STACK
1331                 int dont_block_signals = 0;
1332
1333                 sp = __splitstack_resetcontext(&newg->stack_context[0],
1334                                                &spsize);
1335                 __splitstack_block_signals_context(&newg->stack_context[0],
1336                                                    &dont_block_signals, nil);
1337 #else
1338                 sp = newg->gcinitial_sp;
1339                 spsize = newg->gcstack_size;
1340                 if(spsize == 0)
1341                         runtime_throw("bad spsize in __go_go");
1342                 newg->gcnext_sp = sp;
1343 #endif
1344         } else {
1345                 newg = runtime_malg(StackMin, &sp, &spsize);
1346                 if(runtime_lastg == nil)
1347                         runtime_allg = newg;
1348                 else
1349                         runtime_lastg->alllink = newg;
1350                 runtime_lastg = newg;
1351         }
1352         newg->status = Gwaiting;
1353         newg->waitreason = "new goroutine";
1354
1355         newg->entry = (byte*)fn;
1356         newg->param = arg;
1357         newg->gopc = (uintptr)__builtin_return_address(0);
1358
1359         runtime_sched.gcount++;
1360         runtime_sched.goidgen++;
1361         newg->goid = runtime_sched.goidgen;
1362
1363         if(sp == nil)
1364                 runtime_throw("nil g->stack0");
1365
1366         getcontext(&newg->context);
1367         newg->context.uc_stack.ss_sp = sp;
1368 #ifdef MAKECONTEXT_STACK_TOP
1369         newg->context.uc_stack.ss_sp += spsize;
1370 #endif
1371         newg->context.uc_stack.ss_size = spsize;
1372         makecontext(&newg->context, kickoff, 0);
1373
1374         newprocreadylocked(newg);
1375         schedunlock();
1376
1377         return newg;
1378 //printf(" goid=%d\n", newg->goid);
1379 }
1380
1381 // Put on gfree list.  Sched must be locked.
1382 static void
1383 gfput(G *g)
1384 {
1385         g->schedlink = runtime_sched.gfree;
1386         runtime_sched.gfree = g;
1387 }
1388
1389 // Get from gfree list.  Sched must be locked.
1390 static G*
1391 gfget(void)
1392 {
1393         G *g;
1394
1395         g = runtime_sched.gfree;
1396         if(g)
1397                 runtime_sched.gfree = g->schedlink;
1398         return g;
1399 }
1400
1401 // Run all deferred functions for the current goroutine.
1402 static void
1403 rundefer(void)
1404 {
1405         Defer *d;
1406
1407         while((d = g->defer) != nil) {
1408                 void (*pfn)(void*);
1409
1410                 pfn = d->__pfn;
1411                 d->__pfn = nil;
1412                 if (pfn != nil)
1413                         (*pfn)(d->__arg);
1414                 g->defer = d->__next;
1415                 runtime_free(d);
1416         }
1417 }
1418
1419 void runtime_Goexit (void) asm ("libgo_runtime.runtime.Goexit");
1420
1421 void
1422 runtime_Goexit(void)
1423 {
1424         rundefer();
1425         runtime_goexit();
1426 }
1427
1428 void runtime_Gosched (void) asm ("libgo_runtime.runtime.Gosched");
1429
1430 void
1431 runtime_Gosched(void)
1432 {
1433         runtime_gosched();
1434 }
1435
1436 // Implementation of runtime.GOMAXPROCS.
1437 // delete when scheduler is stronger
1438 int32
1439 runtime_gomaxprocsfunc(int32 n)
1440 {
1441         int32 ret;
1442         uint32 v;
1443
1444         schedlock();
1445         ret = runtime_gomaxprocs;
1446         if(n <= 0)
1447                 n = ret;
1448         if(n > maxgomaxprocs)
1449                 n = maxgomaxprocs;
1450         runtime_gomaxprocs = n;
1451         if(runtime_gomaxprocs > 1)
1452                 runtime_singleproc = false;
1453         if(runtime_gcwaiting != 0) {
1454                 if(atomic_mcpumax(runtime_sched.atomic) != 1)
1455                         runtime_throw("invalid mcpumax during gc");
1456                 schedunlock();
1457                 return ret;
1458         }
1459
1460         setmcpumax(n);
1461
1462         // If there are now fewer allowed procs
1463         // than procs running, stop.
1464         v = runtime_atomicload(&runtime_sched.atomic);
1465         if((int32)atomic_mcpu(v) > n) {
1466                 schedunlock();
1467                 runtime_gosched();
1468                 return ret;
1469         }
1470         // handle more procs
1471         matchmg();
1472         schedunlock();
1473         return ret;
1474 }
1475
1476 void
1477 runtime_LockOSThread(void)
1478 {
1479         if(m == &runtime_m0 && runtime_sched.init) {
1480                 runtime_sched.lockmain = true;
1481                 return;
1482         }
1483         m->lockedg = g;
1484         g->lockedm = m;
1485 }
1486
1487 void
1488 runtime_UnlockOSThread(void)
1489 {
1490         if(m == &runtime_m0 && runtime_sched.init) {
1491                 runtime_sched.lockmain = false;
1492                 return;
1493         }
1494         m->lockedg = nil;
1495         g->lockedm = nil;
1496 }
1497
1498 bool
1499 runtime_lockedOSThread(void)
1500 {
1501         return g->lockedm != nil && m->lockedg != nil;
1502 }
1503
1504 // for testing of callbacks
1505
1506 _Bool runtime_golockedOSThread(void)
1507   asm("libgo_runtime.runtime.golockedOSThread");
1508
1509 _Bool
1510 runtime_golockedOSThread(void)
1511 {
1512         return runtime_lockedOSThread();
1513 }
1514
1515 // for testing of wire, unwire
1516 uint32
1517 runtime_mid()
1518 {
1519         return m->id;
1520 }
1521
1522 int32 runtime_NumGoroutine (void)
1523   __asm__ ("libgo_runtime.runtime.NumGoroutine");
1524
1525 int32
1526 runtime_NumGoroutine()
1527 {
1528         return runtime_sched.gcount;
1529 }
1530
1531 int32
1532 runtime_gcount(void)
1533 {
1534         return runtime_sched.gcount;
1535 }
1536
1537 int32
1538 runtime_mcount(void)
1539 {
1540         return runtime_sched.mcount;
1541 }
1542
1543 static struct {
1544         Lock;
1545         void (*fn)(uintptr*, int32);
1546         int32 hz;
1547         uintptr pcbuf[100];
1548 } prof;
1549
1550 // Called if we receive a SIGPROF signal.
1551 void
1552 runtime_sigprof(uint8 *pc __attribute__ ((unused)),
1553                 uint8 *sp __attribute__ ((unused)),
1554                 uint8 *lr __attribute__ ((unused)),
1555                 G *gp __attribute__ ((unused)))
1556 {
1557         // int32 n;
1558
1559         if(prof.fn == nil || prof.hz == 0)
1560                 return;
1561
1562         runtime_lock(&prof);
1563         if(prof.fn == nil) {
1564                 runtime_unlock(&prof);
1565                 return;
1566         }
1567         // n = runtime_gentraceback(pc, sp, lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf));
1568         // if(n > 0)
1569         //      prof.fn(prof.pcbuf, n);
1570         runtime_unlock(&prof);
1571 }
1572
1573 // Arrange to call fn with a traceback hz times a second.
1574 void
1575 runtime_setcpuprofilerate(void (*fn)(uintptr*, int32), int32 hz)
1576 {
1577         // Force sane arguments.
1578         if(hz < 0)
1579                 hz = 0;
1580         if(hz == 0)
1581                 fn = nil;
1582         if(fn == nil)
1583                 hz = 0;
1584
1585         // Stop profiler on this cpu so that it is safe to lock prof.
1586         // if a profiling signal came in while we had prof locked,
1587         // it would deadlock.
1588         runtime_resetcpuprofiler(0);
1589
1590         runtime_lock(&prof);
1591         prof.fn = fn;
1592         prof.hz = hz;
1593         runtime_unlock(&prof);
1594         runtime_lock(&runtime_sched);
1595         runtime_sched.profilehz = hz;
1596         runtime_unlock(&runtime_sched);
1597
1598         if(hz != 0)
1599                 runtime_resetcpuprofiler(hz);
1600 }