// One round of scheduler: find a goroutine and run it.
// The argument is the goroutine that was running before
// schedule was called, or nil if this is the first call.
// Never returns.
static void
schedule(G *gp)
{
int32 hz;
uint32 v;
schedlock();
if(gp != nil) {
// Just finished running gp.
gp->m = nil;
runtime·sched.grunning--;
// atomic { mcpu-- }
v = runtime·xadd(&runtime·sched.atomic, -1<<mcpuShift);
if(atomic_mcpu(v) > maxgomaxprocs)
runtime·throw("negative mcpu in scheduler");
switch(gp->status){
case Grunnable:
case Gdead:
// Shouldn't have been running!
runtime·throw("bad gp->status in sched");
case Grunning:
gp->status = Grunnable;
gput(gp);
break;
case Gmoribund:
gp->status = Gdead;
if(gp->lockedm) {
gp->lockedm = nil;
m->lockedg = nil;
}
gp->idlem = nil;
unwindstack(gp, nil);
gfput(gp);
if(--runtime·sched.gcount == 0)
runtime·exit(0);
break;
}
if(gp->readyonstop){
gp->readyonstop = 0;
readylocked(gp);
}
} else if(m->helpgc) {
// Bootstrap m or new m started by starttheworld.
// atomic { mcpu-- }
v = runtime·xadd(&runtime·sched.atomic, -1<<mcpuShift);
if(atomic_mcpu(v) > maxgomaxprocs)
runtime·throw("negative mcpu in scheduler");
// Compensate for increment in starttheworld().
runtime·sched.grunning--;
m->helpgc = 0;
} else if(m->nextg != nil) {
// New m started by matchmg.
} else {
runtime·throw("invalid m state in scheduler");
}
// Find (or wait for) g to run. Unlocks runtime·sched.
gp = nextgandunlock();
gp->readyonstop = 0;
gp->status = Grunning;
m->curg = gp;
gp->m = m;
// Check whether the profiler needs to be turned on or off.
hz = runtime·sched.profilehz;
if(m->profilehz != hz)
runtime·resetcpuprofiler(hz);
if(gp->sched.pc == (byte*)runtime·goexit) { // kickoff
runtime·gogocall(&gp->sched, (void(*)(void))gp->entry);
}
runtime·gogo(&gp->sched, 0);
}
// Called from reflect·call or from runtime·morestack when a new
// stack segment is needed. Allocate a new stack big enough for
// m->moreframesize bytes, copy m->moreargsize bytes to the new frame,
// and then act as though runtime·lessstack called the function at
// m->morepc.
void
runtime·newstack(void)
{
int32 framesize, argsize;
Stktop *top;
byte *stk, *sp;
G *g1;
Gobuf label;
bool reflectcall;
uintptr free;
framesize = m->moreframesize;
argsize = m->moreargsize;
g1 = m->curg;
if(m->morebuf.sp < g1->stackguard - StackGuard) {
runtime·printf("runtime: split stack overflow: %p < %p\n", m->morebuf.sp, g1->stackguard - StackGuard);
runtime·throw("runtime: split stack overflow");
}
if(argsize % sizeof(uintptr) != 0) {
runtime·printf("runtime: stack split with misaligned argsize %d\n", argsize);
runtime·throw("runtime: stack split argsize");
}
reflectcall = framesize==1;
if(reflectcall)
framesize = 0;
if(reflectcall && m->morebuf.sp - sizeof(Stktop) - argsize - 32 > g1->stackguard) {
// special case: called from reflect.call (framesize==1)
// to call code with an arbitrary argument size,
// and we have enough space on the current stack.
// the new Stktop* is necessary to unwind, but
// we don't need to create a new segment.
top = (Stktop*)(m->morebuf.sp - sizeof(*top));
stk = g1->stackguard - StackGuard;
free = 0;
} else {
// allocate new segment.
framesize += argsize;
framesize += StackExtra; // room for more functions, Stktop.
if(framesize < StackMin)
framesize = StackMin;
framesize += StackSystem;
stk = runtime·stackalloc(framesize);
top = (Stktop*)(stk+framesize-sizeof(*top));
free = framesize;
}
//runtime·printf("newstack framesize=%d argsize=%d morepc=%p moreargp=%p gobuf=%p, %p top=%p old=%p\n",
//framesize, argsize, m->morepc, m->moreargp, m->morebuf.pc, m->morebuf.sp, top, g1->stackbase);
top->stackbase = g1->stackbase;
top->stackguard = g1->stackguard;
top->gobuf = m->morebuf;
top->argp = m->moreargp;
top->argsize = argsize;
top->free = free;
m->moreargp = nil;
m->morebuf.pc = nil;
m->morebuf.sp = nil;
// copy flag from panic
top->panic = g1->ispanic;
g1->ispanic = false;
g1->stackbase = (byte*)top;
g1->stackguard = stk + StackGuard;
sp = (byte*)top;
if(argsize > 0) {
sp -= argsize;
runtime·memmove(sp, top->argp, argsize);
}
if(thechar == '5') {
// caller would have saved its LR below args.
sp -= sizeof(void*);
*(void**)sp = nil;
}
// Continue as if lessstack had just called m->morepc
// (the PC that decided to grow the stack).
label.sp = sp;
label.pc = (byte*)runtime·lessstack;
label.g = m->curg;
runtime·gogocall(&label, m->morepc);
*(int32*)345 = 123; // never return
}
// Called from reflect·call or from runtime·morestack when a new
// stack segment is needed. Allocate a new stack big enough for
// m->moreframesize bytes, copy m->moreargsize bytes to the new frame,
// and then act as though runtime·lessstack called the function at
// m->morepc.
void
runtime·newstack(void)
{
int32 framesize, minalloc, argsize;
Stktop *top;
byte *stk, *sp;
uintptr *src, *dst, *dstend;
G *gp;
Gobuf label;
bool reflectcall;
uintptr free;
framesize = m->moreframesize;
argsize = m->moreargsize;
gp = m->curg;
if(m->morebuf.sp < gp->stackguard - StackGuard) {
runtime·printf("runtime: split stack overflow: %p < %p\n", m->morebuf.sp, gp->stackguard - StackGuard);
runtime·throw("runtime: split stack overflow");
}
if(argsize % sizeof(uintptr) != 0) {
runtime·printf("runtime: stack split with misaligned argsize %d\n", argsize);
runtime·throw("runtime: stack split argsize");
}
minalloc = 0;
reflectcall = framesize==1;
if(reflectcall) {
framesize = 0;
// moreframesize_minalloc is only set in runtime·gc(),
// that calls newstack via reflect·call().
minalloc = m->moreframesize_minalloc;
m->moreframesize_minalloc = 0;
if(framesize < minalloc)
framesize = minalloc;
}
if(reflectcall && minalloc == 0 && m->morebuf.sp - sizeof(Stktop) - argsize - 32 > gp->stackguard) {
// special case: called from reflect.call (framesize==1)
// to call code with an arbitrary argument size,
// and we have enough space on the current stack.
// the new Stktop* is necessary to unwind, but
// we don't need to create a new segment.
top = (Stktop*)(m->morebuf.sp - sizeof(*top));
stk = (byte*)gp->stackguard - StackGuard;
free = 0;
} else {
// allocate new segment.
framesize += argsize;
framesize += StackExtra; // room for more functions, Stktop.
if(framesize < StackMin)
framesize = StackMin;
framesize += StackSystem;
stk = runtime·stackalloc(framesize);
top = (Stktop*)(stk+framesize-sizeof(*top));
free = framesize;
}
if(0) {
runtime·printf("newstack framesize=%d argsize=%d morepc=%p moreargp=%p gobuf=%p, %p top=%p old=%p\n",
framesize, argsize, m->morepc, m->moreargp, m->morebuf.pc, m->morebuf.sp, top, gp->stackbase);
}
top->stackbase = (byte*)gp->stackbase;
top->stackguard = (byte*)gp->stackguard;
top->gobuf = m->morebuf;
top->argp = m->moreargp;
top->argsize = argsize;
top->free = free;
m->moreargp = nil;
m->morebuf.pc = nil;
m->morebuf.sp = (uintptr)nil;
// copy flag from panic
top->panic = gp->ispanic;
gp->ispanic = false;
gp->stackbase = (uintptr)top;
gp->stackguard = (uintptr)stk + StackGuard;
sp = (byte*)top;
if(argsize > 0) {
sp -= argsize;
dst = (uintptr*)sp;
dstend = dst + argsize/sizeof(*dst);
src = (uintptr*)top->argp;
while(dst < dstend)
*dst++ = *src++;
}
if(thechar == '5') {
// caller would have saved its LR below args.
sp -= sizeof(void*);
*(void**)sp = nil;
}
// Continue as if lessstack had just called m->morepc
// (the PC that decided to grow the stack).
label.sp = (uintptr)sp;
label.pc = (byte*)runtime·lessstack;
label.g = m->curg;
if(reflectcall)
runtime·gogocallfn(&label, (FuncVal*)m->morepc);
else
runtime·gogocall(&label, m->morepc, m->cret);
*(int32*)345 = 123; // never return
}
// Called from reflect·call or from runtime·morestack when a new
// stack segment is needed. Allocate a new stack big enough for
// m->moreframesize bytes, copy m->moreargsize bytes to the new frame,
// and then act as though runtime·lessstack called the function at
// m->morepc.
// 当需要一个新的栈段时调用，被reflect.call或者runtime.morestack调用
// 分配一个足够大的新栈，至少大于m->moreframesize。将m->moreargsize字节复制到新的栈帧。
// 然后伪装成在m->morepc处调用函数runtime.lessstack的样子。
void
runtime·newstack(void)
{
int32 framesize, minalloc, argsize;
Stktop *top;
byte *stk, *sp;
uintptr *src, *dst, *dstend;
G *gp;
Gobuf label;
bool reflectcall;
uintptr free;
framesize = m->moreframesize;
argsize = m->moreargsize;
gp = m->curg;
if(m->morebuf.sp < gp->stackguard - StackGuard) { //栈已经溢出
runtime·printf("runtime: split stack overflow: %p < %p\n", m->morebuf.sp, gp->stackguard - StackGuard);
runtime·throw("runtime: split stack overflow");
}
if(argsize % sizeof(uintptr) != 0) { //参数未对齐
runtime·printf("runtime: stack split with misaligned argsize %d\n", argsize);
runtime·throw("runtime: stack split argsize");
}
minalloc = 0;
reflectcall = framesize==1;
if(reflectcall) {
framesize = 0;
// moreframesize_minalloc is only set in runtime·gc(),
// that calls newstack via reflect·call().
minalloc = m->moreframesize_minalloc;
m->moreframesize_minalloc = 0;
if(framesize < minalloc)
framesize = minalloc;
}
if(reflectcall && minalloc == 0 && m->morebuf.sp - sizeof(Stktop) - argsize - 32 > gp->stackguard) {
// special case: called from reflect.call (framesize==1)
// to call code with an arbitrary argument size,
// and we have enough space on the current stack.
// the new Stktop* is necessary to unwind, but
// we don't need to create a new segment.
top = (Stktop*)(m->morebuf.sp - sizeof(*top));
stk = (byte*)gp->stackguard - StackGuard;
free = 0;
} else {
// 分配新空间
// framesize大小，必须包含参数大小部分，为调用runtime.morestack保留部分，并且至少大于StackMin。然后还要加上StackSystem部分
framesize += argsize;
framesize += StackExtra; // room for more functions, Stktop.
if(framesize < StackMin)
framesize = StackMin;
framesize += StackSystem;
stk = runtime·stackalloc(framesize);
top = (Stktop*)(stk+framesize-sizeof(*top));
free = framesize;
}
if(0) {
runtime·printf("newstack framesize=%d argsize=%d morepc=%p moreargp=%p gobuf=%p, %p top=%p old=%p\n",
framesize, argsize, m->morepc, m->moreargp, m->morebuf.pc, m->morebuf.sp, top, gp->stackbase);
}
//将一些重要信息从结构体g中移到栈顶Stktop中
top->stackbase = (byte*)gp->stackbase;
top->stackguard = (byte*)gp->stackguard;
top->gobuf = m->morebuf; //只是借助m结构体临时传了一下参数，morebuf中记录的是栈空间不够的那个函数的pc,sp,g
top->argp = m->moreargp; //参数
top->argsize = argsize; //参数大小
top->free = free; //可用空间大小
m->moreargp = nil;
m->morebuf.pc = nil;
m->morebuf.sp = (uintptr)nil;
// copy flag from panic
top->panic = gp->ispanic;
gp->ispanic = false;
gp->stackbase = (uintptr)top;
gp->stackguard = (uintptr)stk + StackGuard; //每个goroutine的g->stackguard设置成指向栈底上面StackGuard的位置。
//装饰栈顶的参数区域
sp = (byte*)top;
if(argsize > 0) { //将参数移过来
sp -= argsize;
dst = (uintptr*)sp;
dstend = dst + argsize/sizeof(*dst);
src = (uintptr*)top->argp;
while(dst < dstend)
*dst++ = *src++;
}
if(thechar == '5') { //编译器标识
// caller would have saved its LR below args.
sp -= sizeof(void*);
*(void**)sp = nil;
}
// Continue as if lessstack had just called m->morepc
// (the PC that decided to grow the stack).
// 继续，伪装成好像是从m->morepc中调用lessstack函数的状态
// 跳转
label.sp = (uintptr)sp;
label.pc = (byte*)runtime·lessstack;
label.g = m->curg;
if(reflectcall)
runtime·gogocallfn(&label, (FuncVal*)m->morepc);
else
runtime·gogocall(&label, m->morepc, m->cret); //gogocall相当于一个直接的jmp，不是按函数协议跳转的
*(int32*)345 = 123; // never return
}
// One round of scheduler: find a goroutine and run it.
// The argument is the goroutine that was running before
// schedule was called, or nil if this is the first call.
// Never returns.
static void
schedule(G *gp)
{
int32 hz;
schedlock();
if(gp != nil) {
if(runtime·sched.predawn)
runtime·throw("init rescheduling");
// Just finished running gp.
gp->m = nil;
runtime·sched.mcpu--;
if(runtime·sched.mcpu < 0)
runtime·throw("runtime·sched.mcpu < 0 in scheduler");
switch(gp->status){
case Grunnable:
case Gdead:
// Shouldn't have been running!
runtime·throw("bad gp->status in sched");
case Grunning:
gp->status = Grunnable;
gput(gp);
break;
case Gmoribund:
gp->status = Gdead;
if(gp->lockedm) {
gp->lockedm = nil;
m->lockedg = nil;
}
gp->idlem = nil;
unwindstack(gp, nil);
gfput(gp);
if(--runtime·sched.gcount == 0)
runtime·exit(0);
break;
}
if(gp->readyonstop){
gp->readyonstop = 0;
readylocked(gp);
}
}
// Find (or wait for) g to run. Unlocks runtime·sched.
gp = nextgandunlock();
gp->readyonstop = 0;
gp->status = Grunning;
m->curg = gp;
gp->m = m;
// Check whether the profiler needs to be turned on or off.
hz = runtime·sched.profilehz;
if(m->profilehz != hz)
runtime·resetcpuprofiler(hz);
if(gp->sched.pc == (byte*)runtime·goexit) { // kickoff
runtime·gogocall(&gp->sched, (void(*)(void))gp->entry);
}
runtime·gogo(&gp->sched, 0);
}