Retro68/gcc/libgo/runtime/chan.goc
2015-08-28 17:33:40 +02:00

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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package runtime
#include "runtime.h"
#include "arch.h"
#include "go-type.h"
#include "malloc.h"
#include "chan.h"
uint32 runtime_Hchansize = sizeof(Hchan);
static void dequeueg(WaitQ*);
static SudoG* dequeue(WaitQ*);
static void enqueue(WaitQ*, SudoG*);
static Hchan*
makechan(ChanType *t, int64 hint)
{
Hchan *c;
uintptr n;
const Type *elem;
elem = t->__element_type;
// compiler checks this but be safe.
if(elem->__size >= (1<<16))
runtime_throw("makechan: invalid channel element type");
if(hint < 0 || (intgo)hint != hint || (elem->__size > 0 && (uintptr)hint > (MaxMem - sizeof(*c)) / elem->__size))
runtime_panicstring("makechan: size out of range");
n = sizeof(*c);
n = ROUND(n, elem->__align);
// allocate memory in one call
c = (Hchan*)runtime_mallocgc(sizeof(*c) + hint*elem->__size, (uintptr)t | TypeInfo_Chan, 0);
c->elemsize = elem->__size;
c->elemtype = elem;
c->dataqsiz = hint;
if(debug)
runtime_printf("makechan: chan=%p; elemsize=%D; dataqsiz=%D\n",
c, (int64)elem->__size, (int64)c->dataqsiz);
return c;
}
func reflect.makechan(t *ChanType, size uint64) (c *Hchan) {
c = makechan(t, size);
}
Hchan*
__go_new_channel(ChanType *t, uintptr hint)
{
return makechan(t, hint);
}
Hchan*
__go_new_channel_big(ChanType *t, uint64 hint)
{
return makechan(t, hint);
}
/*
* generic single channel send/recv
* if the bool pointer is nil,
* then the full exchange will
* occur. if pres is not nil,
* then the protocol will not
* sleep but return if it could
* not complete.
*
* sleep can wake up with g->param == nil
* when a channel involved in the sleep has
* been closed. it is easiest to loop and re-run
* the operation; we'll see that it's now closed.
*/
static bool
chansend(ChanType *t, Hchan *c, byte *ep, bool block, void *pc)
{
USED(pc);
SudoG *sg;
SudoG mysg;
G* gp;
int64 t0;
G* g;
g = runtime_g();
if(c == nil) {
USED(t);
if(!block)
return false;
runtime_park(nil, nil, "chan send (nil chan)");
return false; // not reached
}
if(runtime_gcwaiting())
runtime_gosched();
if(debug) {
runtime_printf("chansend: chan=%p\n", c);
}
t0 = 0;
mysg.releasetime = 0;
if(runtime_blockprofilerate > 0) {
t0 = runtime_cputicks();
mysg.releasetime = -1;
}
runtime_lock(c);
if(c->closed)
goto closed;
if(c->dataqsiz > 0)
goto asynch;
sg = dequeue(&c->recvq);
if(sg != nil) {
runtime_unlock(c);
gp = sg->g;
gp->param = sg;
if(sg->elem != nil)
runtime_memmove(sg->elem, ep, c->elemsize);
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
return true;
}
if(!block) {
runtime_unlock(c);
return false;
}
mysg.elem = ep;
mysg.g = g;
mysg.selectdone = nil;
g->param = nil;
enqueue(&c->sendq, &mysg);
runtime_parkunlock(c, "chan send");
if(g->param == nil) {
runtime_lock(c);
if(!c->closed)
runtime_throw("chansend: spurious wakeup");
goto closed;
}
if(mysg.releasetime > 0)
runtime_blockevent(mysg.releasetime - t0, 2);
return true;
asynch:
if(c->closed)
goto closed;
if(c->qcount >= c->dataqsiz) {
if(!block) {
runtime_unlock(c);
return false;
}
mysg.g = g;
mysg.elem = nil;
mysg.selectdone = nil;
enqueue(&c->sendq, &mysg);
runtime_parkunlock(c, "chan send");
runtime_lock(c);
goto asynch;
}
runtime_memmove(chanbuf(c, c->sendx), ep, c->elemsize);
if(++c->sendx == c->dataqsiz)
c->sendx = 0;
c->qcount++;
sg = dequeue(&c->recvq);
if(sg != nil) {
gp = sg->g;
runtime_unlock(c);
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
} else
runtime_unlock(c);
if(mysg.releasetime > 0)
runtime_blockevent(mysg.releasetime - t0, 2);
return true;
closed:
runtime_unlock(c);
runtime_panicstring("send on closed channel");
return false; // not reached
}
static bool
chanrecv(ChanType *t, Hchan* c, byte *ep, bool block, bool *received)
{
SudoG *sg;
SudoG mysg;
G *gp;
int64 t0;
G *g;
if(runtime_gcwaiting())
runtime_gosched();
if(debug)
runtime_printf("chanrecv: chan=%p\n", c);
g = runtime_g();
if(c == nil) {
USED(t);
if(!block)
return false;
runtime_park(nil, nil, "chan receive (nil chan)");
return false; // not reached
}
t0 = 0;
mysg.releasetime = 0;
if(runtime_blockprofilerate > 0) {
t0 = runtime_cputicks();
mysg.releasetime = -1;
}
runtime_lock(c);
if(c->dataqsiz > 0)
goto asynch;
if(c->closed)
goto closed;
sg = dequeue(&c->sendq);
if(sg != nil) {
runtime_unlock(c);
if(ep != nil)
runtime_memmove(ep, sg->elem, c->elemsize);
gp = sg->g;
gp->param = sg;
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
if(received != nil)
*received = true;
return true;
}
if(!block) {
runtime_unlock(c);
return false;
}
mysg.elem = ep;
mysg.g = g;
mysg.selectdone = nil;
g->param = nil;
enqueue(&c->recvq, &mysg);
runtime_parkunlock(c, "chan receive");
if(g->param == nil) {
runtime_lock(c);
if(!c->closed)
runtime_throw("chanrecv: spurious wakeup");
goto closed;
}
if(received != nil)
*received = true;
if(mysg.releasetime > 0)
runtime_blockevent(mysg.releasetime - t0, 2);
return true;
asynch:
if(c->qcount <= 0) {
if(c->closed)
goto closed;
if(!block) {
runtime_unlock(c);
if(received != nil)
*received = false;
return false;
}
mysg.g = g;
mysg.elem = nil;
mysg.selectdone = nil;
enqueue(&c->recvq, &mysg);
runtime_parkunlock(c, "chan receive");
runtime_lock(c);
goto asynch;
}
if(ep != nil)
runtime_memmove(ep, chanbuf(c, c->recvx), c->elemsize);
runtime_memclr(chanbuf(c, c->recvx), c->elemsize);
if(++c->recvx == c->dataqsiz)
c->recvx = 0;
c->qcount--;
sg = dequeue(&c->sendq);
if(sg != nil) {
gp = sg->g;
runtime_unlock(c);
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
} else
runtime_unlock(c);
if(received != nil)
*received = true;
if(mysg.releasetime > 0)
runtime_blockevent(mysg.releasetime - t0, 2);
return true;
closed:
if(ep != nil)
runtime_memclr(ep, c->elemsize);
if(received != nil)
*received = false;
runtime_unlock(c);
if(mysg.releasetime > 0)
runtime_blockevent(mysg.releasetime - t0, 2);
return true;
}
// The compiler generates a call to __go_send_small to send a value 8
// bytes or smaller.
void
__go_send_small(ChanType *t, Hchan* c, uint64 val)
{
union
{
byte b[sizeof(uint64)];
uint64 v;
} u;
byte *v;
u.v = val;
#ifndef WORDS_BIGENDIAN
v = u.b;
#else
v = u.b + sizeof(uint64) - t->__element_type->__size;
#endif
chansend(t, c, v, true, runtime_getcallerpc(&t));
}
// The compiler generates a call to __go_send_big to send a value
// larger than 8 bytes or smaller.
void
__go_send_big(ChanType *t, Hchan* c, byte* v)
{
chansend(t, c, v, true, runtime_getcallerpc(&t));
}
// The compiler generates a call to __go_receive to receive a
// value from a channel.
void
__go_receive(ChanType *t, Hchan* c, byte* v)
{
chanrecv(t, c, v, true, nil);
}
_Bool runtime_chanrecv2(ChanType *t, Hchan* c, byte* v)
__asm__ (GOSYM_PREFIX "runtime.chanrecv2");
_Bool
runtime_chanrecv2(ChanType *t, Hchan* c, byte* v)
{
bool received = false;
chanrecv(t, c, v, true, &received);
return received;
}
// compiler implements
//
// select {
// case c <- v:
// ... foo
// default:
// ... bar
// }
//
// as
//
// if selectnbsend(c, v) {
// ... foo
// } else {
// ... bar
// }
//
func selectnbsend(t *ChanType, c *Hchan, elem *byte) (selected bool) {
selected = chansend(t, c, elem, false, runtime_getcallerpc(&t));
}
// compiler implements
//
// select {
// case v = <-c:
// ... foo
// default:
// ... bar
// }
//
// as
//
// if selectnbrecv(&v, c) {
// ... foo
// } else {
// ... bar
// }
//
func selectnbrecv(t *ChanType, elem *byte, c *Hchan) (selected bool) {
selected = chanrecv(t, c, elem, false, nil);
}
// compiler implements
//
// select {
// case v, ok = <-c:
// ... foo
// default:
// ... bar
// }
//
// as
//
// if c != nil && selectnbrecv2(&v, &ok, c) {
// ... foo
// } else {
// ... bar
// }
//
func selectnbrecv2(t *ChanType, elem *byte, received *bool, c *Hchan) (selected bool) {
bool r;
selected = chanrecv(t, c, elem, false, received == nil ? nil : &r);
if(received != nil)
*received = r;
}
func reflect.chansend(t *ChanType, c *Hchan, elem *byte, nb bool) (selected bool) {
selected = chansend(t, c, elem, !nb, runtime_getcallerpc(&t));
}
func reflect.chanrecv(t *ChanType, c *Hchan, nb bool, elem *byte) (selected bool, received bool) {
received = false;
selected = chanrecv(t, c, elem, !nb, &received);
}
static Select* newselect(int32);
func newselect(size int32) (sel *byte) {
sel = (byte*)newselect(size);
}
static Select*
newselect(int32 size)
{
int32 n;
Select *sel;
n = 0;
if(size > 1)
n = size-1;
// allocate all the memory we need in a single allocation
// start with Select with size cases
// then lockorder with size entries
// then pollorder with size entries
sel = runtime_mal(sizeof(*sel) +
n*sizeof(sel->scase[0]) +
size*sizeof(sel->lockorder[0]) +
size*sizeof(sel->pollorder[0]));
sel->tcase = size;
sel->ncase = 0;
sel->lockorder = (void*)(sel->scase + size);
sel->pollorder = (void*)(sel->lockorder + size);
if(debug)
runtime_printf("newselect s=%p size=%d\n", sel, size);
return sel;
}
// cut in half to give stack a chance to split
static void selectsend(Select *sel, Hchan *c, int index, void *elem);
func selectsend(sel *Select, c *Hchan, elem *byte, index int32) {
// nil cases do not compete
if(c != nil)
selectsend(sel, c, index, elem);
}
static void
selectsend(Select *sel, Hchan *c, int index, void *elem)
{
int32 i;
Scase *cas;
i = sel->ncase;
if(i >= sel->tcase)
runtime_throw("selectsend: too many cases");
sel->ncase = i+1;
cas = &sel->scase[i];
cas->index = index;
cas->chan = c;
cas->kind = CaseSend;
cas->sg.elem = elem;
if(debug)
runtime_printf("selectsend s=%p index=%d chan=%p\n",
sel, cas->index, cas->chan);
}
// cut in half to give stack a chance to split
static void selectrecv(Select *sel, Hchan *c, int index, void *elem, bool*);
func selectrecv(sel *Select, c *Hchan, elem *byte, index int32) {
// nil cases do not compete
if(c != nil)
selectrecv(sel, c, index, elem, nil);
}
func selectrecv2(sel *Select, c *Hchan, elem *byte, received *bool, index int32) {
// nil cases do not compete
if(c != nil)
selectrecv(sel, c, index, elem, received);
}
static void
selectrecv(Select *sel, Hchan *c, int index, void *elem, bool *received)
{
int32 i;
Scase *cas;
i = sel->ncase;
if(i >= sel->tcase)
runtime_throw("selectrecv: too many cases");
sel->ncase = i+1;
cas = &sel->scase[i];
cas->index = index;
cas->chan = c;
cas->kind = CaseRecv;
cas->sg.elem = elem;
cas->receivedp = received;
if(debug)
runtime_printf("selectrecv s=%p index=%d chan=%p\n",
sel, cas->index, cas->chan);
}
// cut in half to give stack a chance to split
static void selectdefault(Select*, int);
func selectdefault(sel *Select, index int32) {
selectdefault(sel, index);
}
static void
selectdefault(Select *sel, int32 index)
{
int32 i;
Scase *cas;
i = sel->ncase;
if(i >= sel->tcase)
runtime_throw("selectdefault: too many cases");
sel->ncase = i+1;
cas = &sel->scase[i];
cas->index = index;
cas->chan = nil;
cas->kind = CaseDefault;
if(debug)
runtime_printf("selectdefault s=%p index=%d\n",
sel, cas->index);
}
static void
sellock(Select *sel)
{
uint32 i;
Hchan *c, *c0;
c = nil;
for(i=0; i<sel->ncase; i++) {
c0 = sel->lockorder[i];
if(c0 && c0 != c) {
c = sel->lockorder[i];
runtime_lock(c);
}
}
}
static void
selunlock(Select *sel)
{
int32 i, n, r;
Hchan *c;
// We must be very careful here to not touch sel after we have unlocked
// the last lock, because sel can be freed right after the last unlock.
// Consider the following situation.
// First M calls runtime_park() in runtime_selectgo() passing the sel.
// Once runtime_park() has unlocked the last lock, another M makes
// the G that calls select runnable again and schedules it for execution.
// When the G runs on another M, it locks all the locks and frees sel.
// Now if the first M touches sel, it will access freed memory.
n = (int32)sel->ncase;
r = 0;
// skip the default case
if(n>0 && sel->lockorder[0] == nil)
r = 1;
for(i = n-1; i >= r; i--) {
c = sel->lockorder[i];
if(i>0 && sel->lockorder[i-1] == c)
continue; // will unlock it on the next iteration
runtime_unlock(c);
}
}
static bool
selparkcommit(G *gp, void *sel)
{
USED(gp);
selunlock(sel);
return true;
}
func block() {
runtime_park(nil, nil, "select (no cases)"); // forever
}
static int selectgo(Select**);
// selectgo(sel *byte);
func selectgo(sel *Select) (ret int32) {
return selectgo(&sel);
}
static int
selectgo(Select **selp)
{
Select *sel;
uint32 o, i, j, k, done;
int64 t0;
Scase *cas, *dfl;
Hchan *c;
SudoG *sg;
G *gp;
int index;
G *g;
sel = *selp;
if(runtime_gcwaiting())
runtime_gosched();
if(debug)
runtime_printf("select: sel=%p\n", sel);
g = runtime_g();
t0 = 0;
if(runtime_blockprofilerate > 0) {
t0 = runtime_cputicks();
for(i=0; i<sel->ncase; i++)
sel->scase[i].sg.releasetime = -1;
}
// The compiler rewrites selects that statically have
// only 0 or 1 cases plus default into simpler constructs.
// The only way we can end up with such small sel->ncase
// values here is for a larger select in which most channels
// have been nilled out. The general code handles those
// cases correctly, and they are rare enough not to bother
// optimizing (and needing to test).
// generate permuted order
for(i=0; i<sel->ncase; i++)
sel->pollorder[i] = i;
for(i=1; i<sel->ncase; i++) {
o = sel->pollorder[i];
j = runtime_fastrand1()%(i+1);
sel->pollorder[i] = sel->pollorder[j];
sel->pollorder[j] = o;
}
// sort the cases by Hchan address to get the locking order.
// simple heap sort, to guarantee n log n time and constant stack footprint.
for(i=0; i<sel->ncase; i++) {
j = i;
c = sel->scase[j].chan;
while(j > 0 && sel->lockorder[k=(j-1)/2] < c) {
sel->lockorder[j] = sel->lockorder[k];
j = k;
}
sel->lockorder[j] = c;
}
for(i=sel->ncase; i-->0; ) {
c = sel->lockorder[i];
sel->lockorder[i] = sel->lockorder[0];
j = 0;
for(;;) {
k = j*2+1;
if(k >= i)
break;
if(k+1 < i && sel->lockorder[k] < sel->lockorder[k+1])
k++;
if(c < sel->lockorder[k]) {
sel->lockorder[j] = sel->lockorder[k];
j = k;
continue;
}
break;
}
sel->lockorder[j] = c;
}
/*
for(i=0; i+1<sel->ncase; i++)
if(sel->lockorder[i] > sel->lockorder[i+1]) {
runtime_printf("i=%d %p %p\n", i, sel->lockorder[i], sel->lockorder[i+1]);
runtime_throw("select: broken sort");
}
*/
sellock(sel);
loop:
// pass 1 - look for something already waiting
dfl = nil;
for(i=0; i<sel->ncase; i++) {
o = sel->pollorder[i];
cas = &sel->scase[o];
c = cas->chan;
switch(cas->kind) {
case CaseRecv:
if(c->dataqsiz > 0) {
if(c->qcount > 0)
goto asyncrecv;
} else {
sg = dequeue(&c->sendq);
if(sg != nil)
goto syncrecv;
}
if(c->closed)
goto rclose;
break;
case CaseSend:
if(c->closed)
goto sclose;
if(c->dataqsiz > 0) {
if(c->qcount < c->dataqsiz)
goto asyncsend;
} else {
sg = dequeue(&c->recvq);
if(sg != nil)
goto syncsend;
}
break;
case CaseDefault:
dfl = cas;
break;
}
}
if(dfl != nil) {
selunlock(sel);
cas = dfl;
goto retc;
}
// pass 2 - enqueue on all chans
done = 0;
for(i=0; i<sel->ncase; i++) {
o = sel->pollorder[i];
cas = &sel->scase[o];
c = cas->chan;
sg = &cas->sg;
sg->g = g;
sg->selectdone = &done;
switch(cas->kind) {
case CaseRecv:
enqueue(&c->recvq, sg);
break;
case CaseSend:
enqueue(&c->sendq, sg);
break;
}
}
g->param = nil;
runtime_park(selparkcommit, sel, "select");
sellock(sel);
sg = g->param;
// pass 3 - dequeue from unsuccessful chans
// otherwise they stack up on quiet channels
for(i=0; i<sel->ncase; i++) {
cas = &sel->scase[i];
if(cas != (Scase*)sg) {
c = cas->chan;
if(cas->kind == CaseSend)
dequeueg(&c->sendq);
else
dequeueg(&c->recvq);
}
}
if(sg == nil)
goto loop;
cas = (Scase*)sg;
c = cas->chan;
if(c->dataqsiz > 0)
runtime_throw("selectgo: shouldn't happen");
if(debug)
runtime_printf("wait-return: sel=%p c=%p cas=%p kind=%d\n",
sel, c, cas, cas->kind);
if(cas->kind == CaseRecv) {
if(cas->receivedp != nil)
*cas->receivedp = true;
}
selunlock(sel);
goto retc;
asyncrecv:
// can receive from buffer
if(cas->receivedp != nil)
*cas->receivedp = true;
if(cas->sg.elem != nil)
runtime_memmove(cas->sg.elem, chanbuf(c, c->recvx), c->elemsize);
runtime_memclr(chanbuf(c, c->recvx), c->elemsize);
if(++c->recvx == c->dataqsiz)
c->recvx = 0;
c->qcount--;
sg = dequeue(&c->sendq);
if(sg != nil) {
gp = sg->g;
selunlock(sel);
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
} else {
selunlock(sel);
}
goto retc;
asyncsend:
// can send to buffer
runtime_memmove(chanbuf(c, c->sendx), cas->sg.elem, c->elemsize);
if(++c->sendx == c->dataqsiz)
c->sendx = 0;
c->qcount++;
sg = dequeue(&c->recvq);
if(sg != nil) {
gp = sg->g;
selunlock(sel);
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
} else {
selunlock(sel);
}
goto retc;
syncrecv:
// can receive from sleeping sender (sg)
selunlock(sel);
if(debug)
runtime_printf("syncrecv: sel=%p c=%p o=%d\n", sel, c, o);
if(cas->receivedp != nil)
*cas->receivedp = true;
if(cas->sg.elem != nil)
runtime_memmove(cas->sg.elem, sg->elem, c->elemsize);
gp = sg->g;
gp->param = sg;
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
goto retc;
rclose:
// read at end of closed channel
selunlock(sel);
if(cas->receivedp != nil)
*cas->receivedp = false;
if(cas->sg.elem != nil)
runtime_memclr(cas->sg.elem, c->elemsize);
goto retc;
syncsend:
// can send to sleeping receiver (sg)
selunlock(sel);
if(debug)
runtime_printf("syncsend: sel=%p c=%p o=%d\n", sel, c, o);
if(sg->elem != nil)
runtime_memmove(sg->elem, cas->sg.elem, c->elemsize);
gp = sg->g;
gp->param = sg;
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
retc:
// return index corresponding to chosen case
index = cas->index;
if(cas->sg.releasetime > 0)
runtime_blockevent(cas->sg.releasetime - t0, 2);
runtime_free(sel);
return index;
sclose:
// send on closed channel
selunlock(sel);
runtime_panicstring("send on closed channel");
return 0; // not reached
}
// This struct must match ../reflect/value.go:/runtimeSelect.
typedef struct runtimeSelect runtimeSelect;
struct runtimeSelect
{
uintptr dir;
ChanType *typ;
Hchan *ch;
byte *val;
};
// This enum must match ../reflect/value.go:/SelectDir.
enum SelectDir {
SelectSend = 1,
SelectRecv,
SelectDefault,
};
func reflect.rselect(cases Slice) (chosen int, recvOK bool) {
int32 i;
Select *sel;
runtimeSelect* rcase, *rc;
chosen = -1;
recvOK = false;
rcase = (runtimeSelect*)cases.__values;
sel = newselect(cases.__count);
for(i=0; i<cases.__count; i++) {
rc = &rcase[i];
switch(rc->dir) {
case SelectDefault:
selectdefault(sel, i);
break;
case SelectSend:
if(rc->ch == nil)
break;
selectsend(sel, rc->ch, i, rc->val);
break;
case SelectRecv:
if(rc->ch == nil)
break;
selectrecv(sel, rc->ch, i, rc->val, &recvOK);
break;
}
}
chosen = (intgo)(uintptr)selectgo(&sel);
}
static void closechan(Hchan *c, void *pc);
func closechan(c *Hchan) {
closechan(c, runtime_getcallerpc(&c));
}
func reflect.chanclose(c *Hchan) {
closechan(c, runtime_getcallerpc(&c));
}
static void
closechan(Hchan *c, void *pc)
{
USED(pc);
SudoG *sg;
G* gp;
if(c == nil)
runtime_panicstring("close of nil channel");
if(runtime_gcwaiting())
runtime_gosched();
runtime_lock(c);
if(c->closed) {
runtime_unlock(c);
runtime_panicstring("close of closed channel");
}
c->closed = true;
// release all readers
for(;;) {
sg = dequeue(&c->recvq);
if(sg == nil)
break;
gp = sg->g;
gp->param = nil;
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
}
// release all writers
for(;;) {
sg = dequeue(&c->sendq);
if(sg == nil)
break;
gp = sg->g;
gp->param = nil;
if(sg->releasetime)
sg->releasetime = runtime_cputicks();
runtime_ready(gp);
}
runtime_unlock(c);
}
void
__go_builtin_close(Hchan *c)
{
runtime_closechan(c);
}
func reflect.chanlen(c *Hchan) (len int) {
if(c == nil)
len = 0;
else
len = c->qcount;
}
intgo
__go_chan_len(Hchan *c)
{
return reflect_chanlen(c);
}
func reflect.chancap(c *Hchan) (cap int) {
if(c == nil)
cap = 0;
else
cap = c->dataqsiz;
}
intgo
__go_chan_cap(Hchan *c)
{
return reflect_chancap(c);
}
static SudoG*
dequeue(WaitQ *q)
{
SudoG *sgp;
loop:
sgp = q->first;
if(sgp == nil)
return nil;
q->first = sgp->link;
// if sgp participates in a select and is already signaled, ignore it
if(sgp->selectdone != nil) {
// claim the right to signal
if(*sgp->selectdone != 0 || !runtime_cas(sgp->selectdone, 0, 1))
goto loop;
}
return sgp;
}
static void
dequeueg(WaitQ *q)
{
SudoG **l, *sgp, *prevsgp;
G *g;
g = runtime_g();
prevsgp = nil;
for(l=&q->first; (sgp=*l) != nil; l=&sgp->link, prevsgp=sgp) {
if(sgp->g == g) {
*l = sgp->link;
if(q->last == sgp)
q->last = prevsgp;
break;
}
}
}
static void
enqueue(WaitQ *q, SudoG *sgp)
{
sgp->link = nil;
if(q->first == nil) {
q->first = sgp;
q->last = sgp;
return;
}
q->last->link = sgp;
q->last = sgp;
}