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.
17 #ifdef USING_SPLIT_STACK
19 /* FIXME: These are not declared anywhere. */
21 extern void __splitstack_getcontext(void *context
[10]);
23 extern void __splitstack_setcontext(void *context
[10]);
25 extern void *__splitstack_makecontext(size_t, void *context
[10], size_t *);
27 extern void * __splitstack_resetcontext(void *context
[10], size_t *);
29 extern void *__splitstack_find(void *, void *, size_t *, void **, void **,
32 extern void __splitstack_block_signals (int *, int *);
34 extern void __splitstack_block_signals_context (void *context
[10], int *,
39 #if defined(USING_SPLIT_STACK) && defined(LINKER_SUPPORTS_SPLIT_STACK)
40 # ifdef PTHREAD_STACK_MIN
41 # define StackMin PTHREAD_STACK_MIN
43 # define StackMin 8192
46 # define StackMin 2 * 1024 * 1024
49 uintptr runtime_stacks_sys
;
51 static void schedule(G
*);
53 typedef struct Sched Sched
;
56 G runtime_g0
; // idle goroutine for m0
65 #ifndef SETCONTEXT_CLOBBERS_TLS
73 fixcontext(ucontext_t
*c
__attribute__ ((unused
)))
79 # if defined(__x86_64__) && defined(__sun__)
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
88 static __thread greg_t fs
;
96 fs
= c
.uc_mcontext
.gregs
[REG_FSBASE
];
100 fixcontext(ucontext_t
* c
)
102 c
->uc_mcontext
.gregs
[REG_FSBASE
] = fs
;
107 # error unknown case for SETCONTEXT_CLOBBERS_TLS
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
121 G
* runtime_g(void) __attribute__ ((noinline
, no_split_stack
));
129 M
* runtime_m(void) __attribute__ ((noinline
, no_split_stack
));
137 int32 runtime_gcwaiting
;
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.
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.
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.
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
169 G
*gfree
; // available g's (status == Gdead)
172 G
*ghead
; // g's waiting to run
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
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
182 volatile uint32 atomic
; // atomic scheduling word (see below)
184 int32 profilehz
; // cpu profiling rate
186 bool init
; // running initialization
187 bool lockmain
; // init called runtime.LockOSThread
189 Note stopped
; // one g can set waitstop and wait here for m's to stop
192 // The atomic word in sched is an atomic uint32 that
193 // holds these fields.
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
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.
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).
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.
221 mcpuMask
= (1<<mcpuWidth
) - 1,
223 mcpumaxShift
= mcpuShift
+ mcpuWidth
,
224 waitstopShift
= mcpumaxShift
+ mcpuWidth
,
225 gwaitingShift
= waitstopShift
+1,
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
232 maxgomaxprocs
= mcpuMask
- 10,
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)
241 int32 runtime_gomaxprocs
;
242 bool runtime_singleproc
;
244 static bool canaddmcpu(void);
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.
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
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
*);
271 v
= runtime_sched
.atomic
;
273 w
&= ~(mcpuMask
<<mcpumaxShift
);
274 w
|= n
<<mcpumaxShift
;
275 if(runtime_cas(&runtime_sched
.atomic
, v
, w
))
280 // First function run by a new goroutine. This replaces gogocall.
286 fn
= (void (*)(void*))(g
->entry
);
291 // Switch context to a different goroutine. This is like longjmp.
292 static void runtime_gogo(G
*) __attribute__ ((noinline
));
294 runtime_gogo(G
* newg
)
296 #ifdef USING_SPLIT_STACK
297 __splitstack_setcontext(&newg
->stack_context
[0]);
300 newg
->fromgogo
= true;
301 fixcontext(&newg
->context
);
302 setcontext(&newg
->context
);
303 runtime_throw("gogo setcontext returned");
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
));
312 runtime_mcall(void (*pfn
)(G
*))
316 #ifndef USING_SPLIT_STACK
320 // Ensure that all registers are on the stack for the garbage
322 __builtin_unwind_init();
327 runtime_throw("runtime: mcall called on m->g0 stack");
331 #ifdef USING_SPLIT_STACK
332 __splitstack_getcontext(&g
->stack_context
[0]);
336 gp
->fromgogo
= false;
337 getcontext(&gp
->context
);
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.
349 if (gp
== nil
|| !gp
->fromgogo
) {
350 #ifdef USING_SPLIT_STACK
351 __splitstack_setcontext(&mp
->g0
->stack_context
[0]);
353 mp
->g0
->entry
= (byte
*)pfn
;
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.
361 fixcontext(&mp
->g0
->context
);
362 setcontext(&mp
->g0
->context
);
363 runtime_throw("runtime: mcall function returned");
367 // Keep trace of scavenger's goroutine for deadlock detection.
370 // The bootstrap sequence is:
374 // make & queue new G
375 // call runtime_mstart
377 // The new G calls runtime_main.
379 runtime_schedinit(void)
393 runtime_mallocinit();
400 // Allocate internal symbol table representation now,
401 // so that we don't need to call malloc when we crash.
402 // runtime_findfunc(0);
404 runtime_gomaxprocs
= 1;
405 p
= runtime_getenv("GOMAXPROCS");
406 if(p
!= nil
&& (n
= runtime_atoi(p
)) != 0) {
407 if(n
> maxgomaxprocs
)
409 runtime_gomaxprocs
= n
;
411 // wait for the main goroutine to start before taking
412 // GOMAXPROCS into account.
414 runtime_singleproc
= runtime_gomaxprocs
== 1;
416 canaddmcpu(); // mcpu++ to account for bootstrap m
417 m
->helpgc
= 1; // flag to tell schedule() to mcpu--
418 runtime_sched
.grunning
++;
420 // Can not enable GC until all roots are registered.
421 // mstats.enablegc = 1;
425 extern void main_init(void) __asm__ ("__go_init_main");
426 extern void main_main(void) __asm__ ("main.main");
428 // The main goroutine.
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
);
444 runtime_sched
.init
= false;
445 if(!runtime_sched
.lockmain
)
446 runtime_UnlockOSThread();
448 // For gccgo we have to wait until after main is initialized
449 // to enable GC, because initializing main registers the GC
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{} }.
464 // Lock the scheduler.
468 runtime_lock(&runtime_sched
);
471 // Unlock the scheduler.
479 runtime_unlock(&runtime_sched
);
481 runtime_notewakeup(&m
->havenextg
);
487 g
->status
= Gmoribund
;
492 runtime_goroutineheader(G
*g
)
511 status
= g
->waitreason
;
522 runtime_printf("goroutine %d [%s]:\n", g
->goid
, status
);
526 runtime_tracebackothers(G
*me
)
530 for(g
= runtime_allg
; g
!= nil
; g
= g
->alllink
) {
531 if(g
== me
|| g
->status
== Gdead
)
533 runtime_printf("\n");
534 runtime_goroutineheader(g
);
535 // runtime_traceback(g->sched.pc, g->sched.sp, 0, g);
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.
544 runtime_idlegoroutine(void)
547 runtime_throw("g is already an idle goroutine");
554 m
->id
= runtime_sched
.mcount
++;
555 m
->fastrand
= 0x49f6428aUL
+ m
->id
+ runtime_cputicks();
558 m
->mcache
= runtime_allocmcache();
560 runtime_callers(1, m
->createstack
, nelem(m
->createstack
));
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
);
570 // Try to increment mcpu. Report whether succeeded.
577 v
= runtime_sched
.atomic
;
578 if(atomic_mcpu(v
) >= atomic_mcpumax(v
))
580 if(runtime_cas(&runtime_sched
.atomic
, v
, v
+(1<<mcpuShift
)))
585 // Put on `g' queue. Sched must be locked.
591 // If g is wired, hand it off directly.
592 if((m
= g
->lockedm
) != nil
&& canaddmcpu()) {
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",
602 g
->idlem
->idleg
->goid
, g
->goid
);
603 runtime_throw("runtime: double idle");
610 if(runtime_sched
.ghead
== nil
)
611 runtime_sched
.ghead
= g
;
613 runtime_sched
.gtail
->schedlink
= g
;
614 runtime_sched
.gtail
= g
;
617 // if it transitions to nonzero, set atomic gwaiting bit.
618 if(runtime_sched
.gwait
++ == 0)
619 runtime_xadd(&runtime_sched
.atomic
, 1<<gwaitingShift
);
622 // Report whether gget would return something.
626 return runtime_sched
.ghead
!= nil
|| m
->idleg
!= nil
;
629 // Get from `g' queue. Sched must be locked.
635 g
= runtime_sched
.ghead
;
637 runtime_sched
.ghead
= g
->schedlink
;
638 if(runtime_sched
.ghead
== nil
)
639 runtime_sched
.gtail
= nil
;
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
) {
651 // Put on `m' list. Sched must be locked.
655 m
->schedlink
= runtime_sched
.mhead
;
656 runtime_sched
.mhead
= m
;
657 runtime_sched
.mwait
++;
660 // Get an `m' to run `g'. Sched must be locked.
666 // if g has its own m, use it.
667 if(g
&& (m
= g
->lockedm
) != nil
)
670 // otherwise use general m pool.
671 if((m
= runtime_sched
.mhead
) != nil
){
672 runtime_sched
.mhead
= m
->schedlink
;
673 runtime_sched
.mwait
--;
678 // Mark g ready to run.
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.
694 // Running on another machine.
695 // Ready it when it stops.
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");
705 g
->status
= Grunnable
;
711 // Same as readylocked but a different symbol so that
712 // debuggers can set a breakpoint here and catch all
715 newprocreadylocked(G
*g
)
720 // Pass g to m for running.
721 // Caller has already incremented mcpu.
725 runtime_sched
.grunning
++;
730 runtime_notewakeup(&mwakeup
->havenextg
);
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.
746 if(atomic_mcpu(runtime_sched
.atomic
) >= maxgomaxprocs
)
747 runtime_throw("negative mcpu");
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
) {
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) {
764 // m->lockedg might have been on the queue.
765 if(m
->nextg
!= nil
) {
773 // Look for work on global queue.
774 while(haveg() && canaddmcpu()) {
777 runtime_throw("gget inconsistency");
780 mnextg(gp
->lockedm
, gp
);
783 runtime_sched
.grunning
++;
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.
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.
800 // Wait on global m queue.
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.
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.
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!");
827 runtime_noteclear(&m
->havenextg
);
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
);
841 runtime_notesleep(&m
->havenextg
);
845 runtime_lock(&runtime_sched
);
848 if((gp
= m
->nextg
) == nil
)
849 runtime_throw("bad m->nextg in nextgoroutine");
855 runtime_helpgc(bool *extra
)
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;
868 // We're going to use one CPU no matter what.
869 // Figure out the max number of additional CPUs.
872 runtime_lock(&runtime_sched
);
874 while(n
< max
&& (mp
= mget(nil
)) != nil
) {
878 runtime_notewakeup(&mp
->havenextg
);
880 runtime_unlock(&runtime_sched
);
887 runtime_stoptheworld(void)
892 runtime_gcwaiting
= 1;
898 v
= runtime_sched
.atomic
;
899 if(atomic_mcpu(v
) <= 1)
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");
909 // atomic { waitstop = 1 }, predicated on mcpu <= 1 check above
911 if(!runtime_cas(&runtime_sched
.atomic
, v
, v
+(1<<waitstopShift
)))
915 runtime_notesleep(&runtime_sched
.stopped
);
918 runtime_singleproc
= runtime_gomaxprocs
== 1;
923 runtime_starttheworld(bool extra
)
928 runtime_gcwaiting
= 0;
929 setmcpumax(runtime_gomaxprocs
);
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--.
943 runtime_sched
.grunning
++;
948 // Called to start an M.
950 runtime_mstart(void* mp
)
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]);
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.
972 getcontext(&g
->context
);
974 if(g
->entry
!= nil
) {
975 // Got here from mcall.
976 void (*pfn
)(G
*) = (void (*)(G
*))g
->entry
;
977 G
* gp
= (G
*)g
->param
;
983 #ifdef USING_SPLIT_STACK
985 int dont_block_signals
= 0;
986 __splitstack_block_signals(&dont_block_signals
, nil
);
990 // Install signal handlers; after minit so that minit can
991 // prepare the thread to be able to handle the signals.
999 typedef struct CgoThreadStart CgoThreadStart
;
1000 struct CgoThreadStart
1007 // Kick off new m's as needed (up to mcpumax).
1015 if(m
->mallocing
|| m
->gcing
)
1018 while(haveg() && canaddmcpu()) {
1021 runtime_throw("gget inconsistency");
1023 // Find the m that will run gp.
1024 if((mp
= mget(gp
)) == nil
)
1025 mp
= runtime_newm();
1030 // Create a new m. It will start off with a call to runtime_mstart.
1035 pthread_attr_t attr
;
1038 m
= runtime_malloc(sizeof(M
));
1040 m
->g0
= runtime_malg(-1, nil
, nil
);
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");
1047 #ifndef PTHREAD_STACK_MIN
1048 #define PTHREAD_STACK_MIN 8192
1050 if(pthread_attr_setstacksize(&attr
, PTHREAD_STACK_MIN
) != 0)
1051 runtime_throw("pthread_attr_setstacksize");
1053 if(pthread_create(&tid
, &attr
, runtime_mstart
, m
) != 0)
1054 runtime_throw("pthread_create");
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.
1071 // Just finished running gp.
1073 runtime_sched
.grunning
--;
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");
1083 // Shouldn't have been running!
1084 runtime_throw("bad gp->status in sched");
1086 gp
->status
= Grunnable
;
1096 runtime_memclr(&gp
->context
, sizeof gp
->context
);
1098 if(--runtime_sched
.gcount
== 0)
1102 if(gp
->readyonstop
){
1103 gp
->readyonstop
= 0;
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
--;
1115 } else if(m
->nextg
!= nil
) {
1116 // New m started by matchmg.
1118 runtime_throw("invalid m state in scheduler");
1121 // Find (or wait for) g to run. Unlocks runtime_sched.
1122 gp
= nextgandunlock();
1123 gp
->readyonstop
= 0;
1124 gp
->status
= Grunning
;
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
);
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,
1141 runtime_gosched(void)
1144 runtime_throw("gosched holding locks");
1146 runtime_throw("gosched of g0");
1147 runtime_mcall(schedule
);
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.
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.
1162 void runtime_entersyscall(void) __attribute__ ((no_split_stack
));
1165 runtime_entersyscall(void)
1169 if(m
->profilehz
> 0)
1170 runtime_setprof(false);
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
,
1178 g
->gcnext_sp
= (byte
*) &v
;
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.
1187 g
->status
= Gsyscall
;
1190 // The slow path inside the schedlock/schedunlock will get
1191 // through without stopping if it does:
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
)))
1202 v
= runtime_atomicload(&runtime_sched
.atomic
);
1203 if(atomic_gwaiting(v
)) {
1205 v
= runtime_atomicload(&runtime_sched
.atomic
);
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
);
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.
1220 runtime_exitsyscall(void)
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.
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
1240 gp
->gcnext_sp
= nil
;
1241 runtime_memclr(gp
->gcregs
, sizeof gp
->gcregs
);
1243 if(m
->profilehz
> 0)
1244 runtime_setprof(true);
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;
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.
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
1266 #ifdef USING_SPLIT_STACK
1269 gp
->gcnext_sp
= nil
;
1270 runtime_memclr(gp
->gcregs
, sizeof gp
->gcregs
);
1273 // Allocate a new g, with a stack big enough for stacksize bytes.
1275 runtime_malg(int32 stacksize
, byte
** ret_stack
, size_t* ret_stacksize
)
1279 newg
= runtime_malloc(sizeof(G
));
1280 if(stacksize
>= 0) {
1281 #if USING_SPLIT_STACK
1282 int dont_block_signals
= 0;
1284 *ret_stack
= __splitstack_makecontext(stacksize
,
1285 &newg
->stack_context
[0],
1287 __splitstack_block_signals_context(&newg
->stack_context
[0],
1288 &dont_block_signals
, nil
);
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
);
1300 /* For runtime package testing. */
1302 void runtime_testing_entersyscall(void)
1303 __asm__("libgo_runtime.runtime.entersyscall");
1306 runtime_testing_entersyscall()
1308 runtime_entersyscall();
1311 void runtime_testing_exitsyscall(void)
1312 __asm__("libgo_runtime.runtime.exitsyscall");
1315 runtime_testing_exitsyscall()
1317 runtime_exitsyscall();
1321 __go_go(void (*fn
)(void*), void* arg
)
1325 G
* volatile newg
; // volatile to avoid longjmp warning
1329 if((newg
= gfget()) != nil
){
1330 #ifdef USING_SPLIT_STACK
1331 int dont_block_signals
= 0;
1333 sp
= __splitstack_resetcontext(&newg
->stack_context
[0],
1335 __splitstack_block_signals_context(&newg
->stack_context
[0],
1336 &dont_block_signals
, nil
);
1338 sp
= newg
->gcinitial_sp
;
1339 spsize
= newg
->gcstack_size
;
1341 runtime_throw("bad spsize in __go_go");
1342 newg
->gcnext_sp
= sp
;
1345 newg
= runtime_malg(StackMin
, &sp
, &spsize
);
1346 if(runtime_lastg
== nil
)
1347 runtime_allg
= newg
;
1349 runtime_lastg
->alllink
= newg
;
1350 runtime_lastg
= newg
;
1352 newg
->status
= Gwaiting
;
1353 newg
->waitreason
= "new goroutine";
1355 newg
->entry
= (byte
*)fn
;
1357 newg
->gopc
= (uintptr
)__builtin_return_address(0);
1359 runtime_sched
.gcount
++;
1360 runtime_sched
.goidgen
++;
1361 newg
->goid
= runtime_sched
.goidgen
;
1364 runtime_throw("nil g->stack0");
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
;
1371 newg
->context
.uc_stack
.ss_size
= spsize
;
1372 makecontext(&newg
->context
, kickoff
, 0);
1374 newprocreadylocked(newg
);
1378 //printf(" goid=%d\n", newg->goid);
1381 // Put on gfree list. Sched must be locked.
1385 g
->schedlink
= runtime_sched
.gfree
;
1386 runtime_sched
.gfree
= g
;
1389 // Get from gfree list. Sched must be locked.
1395 g
= runtime_sched
.gfree
;
1397 runtime_sched
.gfree
= g
->schedlink
;
1401 // Run all deferred functions for the current goroutine.
1407 while((d
= g
->defer
) != nil
) {
1414 g
->defer
= d
->__next
;
1419 void runtime_Goexit (void) asm ("libgo_runtime.runtime.Goexit");
1422 runtime_Goexit(void)
1428 void runtime_Gosched (void) asm ("libgo_runtime.runtime.Gosched");
1431 runtime_Gosched(void)
1436 // Implementation of runtime.GOMAXPROCS.
1437 // delete when scheduler is stronger
1439 runtime_gomaxprocsfunc(int32 n
)
1445 ret
= runtime_gomaxprocs
;
1448 if(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");
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
) {
1470 // handle more procs
1477 runtime_LockOSThread(void)
1479 if(m
== &runtime_m0
&& runtime_sched
.init
) {
1480 runtime_sched
.lockmain
= true;
1488 runtime_UnlockOSThread(void)
1490 if(m
== &runtime_m0
&& runtime_sched
.init
) {
1491 runtime_sched
.lockmain
= false;
1499 runtime_lockedOSThread(void)
1501 return g
->lockedm
!= nil
&& m
->lockedg
!= nil
;
1504 // for testing of callbacks
1506 _Bool
runtime_golockedOSThread(void)
1507 asm("libgo_runtime.runtime.golockedOSThread");
1510 runtime_golockedOSThread(void)
1512 return runtime_lockedOSThread();
1515 // for testing of wire, unwire
1522 int32
runtime_NumGoroutine (void)
1523 __asm__ ("libgo_runtime.runtime.NumGoroutine");
1526 runtime_NumGoroutine()
1528 return runtime_sched
.gcount
;
1532 runtime_gcount(void)
1534 return runtime_sched
.gcount
;
1538 runtime_mcount(void)
1540 return runtime_sched
.mcount
;
1545 void (*fn
)(uintptr
*, int32
);
1550 // Called if we receive a SIGPROF signal.
1552 runtime_sigprof(uint8
*pc
__attribute__ ((unused
)),
1553 uint8
*sp
__attribute__ ((unused
)),
1554 uint8
*lr
__attribute__ ((unused
)),
1555 G
*gp
__attribute__ ((unused
)))
1559 if(prof
.fn
== nil
|| prof
.hz
== 0)
1562 runtime_lock(&prof
);
1563 if(prof
.fn
== nil
) {
1564 runtime_unlock(&prof
);
1567 // n = runtime_gentraceback(pc, sp, lr, gp, 0, prof.pcbuf, nelem(prof.pcbuf));
1569 // prof.fn(prof.pcbuf, n);
1570 runtime_unlock(&prof
);
1573 // Arrange to call fn with a traceback hz times a second.
1575 runtime_setcpuprofilerate(void (*fn
)(uintptr
*, int32
), int32 hz
)
1577 // Force sane arguments.
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);
1590 runtime_lock(&prof
);
1593 runtime_unlock(&prof
);
1594 runtime_lock(&runtime_sched
);
1595 runtime_sched
.profilehz
= hz
;
1596 runtime_unlock(&runtime_sched
);
1599 runtime_resetcpuprofiler(hz
);