[dev.garbage] all: merge dev.cc into dev.garbage
The garbage collector is now written in Go.
There is plenty to clean up (just like on dev.cc).
all.bash passes on darwin/amd64, darwin/386, linux/amd64, linux/386.
TBR=rlh
R=austin, rlh, bradfitz
CC=golang-codereviews
https://golang.org/cl/173250043
diff --git a/src/runtime/stack1.go b/src/runtime/stack1.go
new file mode 100644
index 0000000..963f4fa
--- /dev/null
+++ b/src/runtime/stack1.go
@@ -0,0 +1,818 @@
+// Copyright 2013 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
+
+import "unsafe"
+
+const (
+ // StackDebug == 0: no logging
+ // == 1: logging of per-stack operations
+ // == 2: logging of per-frame operations
+ // == 3: logging of per-word updates
+ // == 4: logging of per-word reads
+ stackDebug = 0
+ stackFromSystem = 0 // allocate stacks from system memory instead of the heap
+ stackFaultOnFree = 0 // old stacks are mapped noaccess to detect use after free
+ stackPoisonCopy = 0 // fill stack that should not be accessed with garbage, to detect bad dereferences during copy
+
+ stackCache = 1
+)
+
+const (
+ uintptrMask = 1<<(8*ptrSize) - 1
+ poisonGC = uintptrMask & 0xf969696969696969
+ poisonStack = uintptrMask & 0x6868686868686868
+
+ // Goroutine preemption request.
+ // Stored into g->stackguard0 to cause split stack check failure.
+ // Must be greater than any real sp.
+ // 0xfffffade in hex.
+ stackPreempt = uintptrMask & -1314
+
+ // Thread is forking.
+ // Stored into g->stackguard0 to cause split stack check failure.
+ // Must be greater than any real sp.
+ stackFork = uintptrMask & -1234
+)
+
+// Global pool of spans that have free stacks.
+// Stacks are assigned an order according to size.
+// order = log_2(size/FixedStack)
+// There is a free list for each order.
+// TODO: one lock per order?
+var stackpool [_NumStackOrders]mspan
+var stackpoolmu mutex
+
+var stackfreequeue stack
+
+func stackinit() {
+ if _StackCacheSize&_PageMask != 0 {
+ gothrow("cache size must be a multiple of page size")
+ }
+ for i := range stackpool {
+ mSpanList_Init(&stackpool[i])
+ }
+}
+
+// Allocates a stack from the free pool. Must be called with
+// stackpoolmu held.
+func stackpoolalloc(order uint8) *mlink {
+ list := &stackpool[order]
+ s := list.next
+ if s == list {
+ // no free stacks. Allocate another span worth.
+ s = mHeap_AllocStack(&mheap_, _StackCacheSize>>_PageShift)
+ if s == nil {
+ gothrow("out of memory")
+ }
+ if s.ref != 0 {
+ gothrow("bad ref")
+ }
+ if s.freelist != nil {
+ gothrow("bad freelist")
+ }
+ for i := uintptr(0); i < _StackCacheSize; i += _FixedStack << order {
+ x := (*mlink)(unsafe.Pointer(uintptr(s.start)<<_PageShift + i))
+ x.next = s.freelist
+ s.freelist = x
+ }
+ mSpanList_Insert(list, s)
+ }
+ x := s.freelist
+ if x == nil {
+ gothrow("span has no free stacks")
+ }
+ s.freelist = x.next
+ s.ref++
+ if s.freelist == nil {
+ // all stacks in s are allocated.
+ mSpanList_Remove(s)
+ }
+ return x
+}
+
+// Adds stack x to the free pool. Must be called with stackpoolmu held.
+func stackpoolfree(x *mlink, order uint8) {
+ s := mHeap_Lookup(&mheap_, (unsafe.Pointer)(x))
+ if s.state != _MSpanStack {
+ gothrow("freeing stack not in a stack span")
+ }
+ if s.freelist == nil {
+ // s will now have a free stack
+ mSpanList_Insert(&stackpool[order], s)
+ }
+ x.next = s.freelist
+ s.freelist = x
+ s.ref--
+ if s.ref == 0 {
+ // span is completely free - return to heap
+ mSpanList_Remove(s)
+ s.freelist = nil
+ mHeap_FreeStack(&mheap_, s)
+ }
+}
+
+// stackcacherefill/stackcacherelease implement a global pool of stack segments.
+// The pool is required to prevent unlimited growth of per-thread caches.
+func stackcacherefill(c *mcache, order uint8) {
+ if stackDebug >= 1 {
+ print("stackcacherefill order=", order, "\n")
+ }
+
+ // Grab some stacks from the global cache.
+ // Grab half of the allowed capacity (to prevent thrashing).
+ var list *mlink
+ var size uintptr
+ lock(&stackpoolmu)
+ for size < _StackCacheSize/2 {
+ x := stackpoolalloc(order)
+ x.next = list
+ list = x
+ size += _FixedStack << order
+ }
+ unlock(&stackpoolmu)
+ c.stackcache[order].list = list
+ c.stackcache[order].size = size
+}
+
+func stackcacherelease(c *mcache, order uint8) {
+ if stackDebug >= 1 {
+ print("stackcacherelease order=", order, "\n")
+ }
+ x := c.stackcache[order].list
+ size := c.stackcache[order].size
+ lock(&stackpoolmu)
+ for size > _StackCacheSize/2 {
+ y := x.next
+ stackpoolfree(x, order)
+ x = y
+ size -= _FixedStack << order
+ }
+ unlock(&stackpoolmu)
+ c.stackcache[order].list = x
+ c.stackcache[order].size = size
+}
+
+func stackcache_clear(c *mcache) {
+ if stackDebug >= 1 {
+ print("stackcache clear\n")
+ }
+ lock(&stackpoolmu)
+ for order := uint8(0); order < _NumStackOrders; order++ {
+ x := c.stackcache[order].list
+ for x != nil {
+ y := x.next
+ stackpoolfree(x, order)
+ x = y
+ }
+ c.stackcache[order].list = nil
+ c.stackcache[order].size = 0
+ }
+ unlock(&stackpoolmu)
+}
+
+func stackalloc(n uint32) stack {
+ // Stackalloc must be called on scheduler stack, so that we
+ // never try to grow the stack during the code that stackalloc runs.
+ // Doing so would cause a deadlock (issue 1547).
+ thisg := getg()
+ if thisg != thisg.m.g0 {
+ gothrow("stackalloc not on scheduler stack")
+ }
+ if n&(n-1) != 0 {
+ gothrow("stack size not a power of 2")
+ }
+ if stackDebug >= 1 {
+ print("stackalloc ", n, "\n")
+ }
+
+ if debug.efence != 0 || stackFromSystem != 0 {
+ v := sysAlloc(round(uintptr(n), _PageSize), &memstats.stacks_sys)
+ if v == nil {
+ gothrow("out of memory (stackalloc)")
+ }
+ return stack{uintptr(v), uintptr(v) + uintptr(n)}
+ }
+
+ // Small stacks are allocated with a fixed-size free-list allocator.
+ // If we need a stack of a bigger size, we fall back on allocating
+ // a dedicated span.
+ var v unsafe.Pointer
+ if stackCache != 0 && n < _FixedStack<<_NumStackOrders && n < _StackCacheSize {
+ order := uint8(0)
+ n2 := n
+ for n2 > _FixedStack {
+ order++
+ n2 >>= 1
+ }
+ var x *mlink
+ c := thisg.m.mcache
+ if c == nil || thisg.m.gcing != 0 || thisg.m.helpgc != 0 {
+ // c == nil can happen in the guts of exitsyscall or
+ // procresize. Just get a stack from the global pool.
+ // Also don't touch stackcache during gc
+ // as it's flushed concurrently.
+ lock(&stackpoolmu)
+ x = stackpoolalloc(order)
+ unlock(&stackpoolmu)
+ } else {
+ x = c.stackcache[order].list
+ if x == nil {
+ stackcacherefill(c, order)
+ x = c.stackcache[order].list
+ }
+ c.stackcache[order].list = x.next
+ c.stackcache[order].size -= uintptr(n)
+ }
+ v = (unsafe.Pointer)(x)
+ } else {
+ s := mHeap_AllocStack(&mheap_, round(uintptr(n), _PageSize)>>_PageShift)
+ if s == nil {
+ gothrow("out of memory")
+ }
+ v = (unsafe.Pointer)(s.start << _PageShift)
+ }
+
+ if raceenabled {
+ racemalloc(v, uintptr(n))
+ }
+ if stackDebug >= 1 {
+ print(" allocated ", v, "\n")
+ }
+ return stack{uintptr(v), uintptr(v) + uintptr(n)}
+}
+
+func stackfree(stk stack) {
+ gp := getg()
+ n := stk.hi - stk.lo
+ v := (unsafe.Pointer)(stk.lo)
+ if n&(n-1) != 0 {
+ gothrow("stack not a power of 2")
+ }
+ if stackDebug >= 1 {
+ println("stackfree", v, n)
+ memclr(v, n) // for testing, clobber stack data
+ }
+ if debug.efence != 0 || stackFromSystem != 0 {
+ if debug.efence != 0 || stackFaultOnFree != 0 {
+ sysFault(v, n)
+ } else {
+ sysFree(v, n, &memstats.stacks_sys)
+ }
+ return
+ }
+ if stackCache != 0 && n < _FixedStack<<_NumStackOrders && n < _StackCacheSize {
+ order := uint8(0)
+ n2 := n
+ for n2 > _FixedStack {
+ order++
+ n2 >>= 1
+ }
+ x := (*mlink)(v)
+ c := gp.m.mcache
+ if c == nil || gp.m.gcing != 0 || gp.m.helpgc != 0 {
+ lock(&stackpoolmu)
+ stackpoolfree(x, order)
+ unlock(&stackpoolmu)
+ } else {
+ if c.stackcache[order].size >= _StackCacheSize {
+ stackcacherelease(c, order)
+ }
+ x.next = c.stackcache[order].list
+ c.stackcache[order].list = x
+ c.stackcache[order].size += n
+ }
+ } else {
+ s := mHeap_Lookup(&mheap_, v)
+ if s.state != _MSpanStack {
+ println(hex(s.start<<_PageShift), v)
+ gothrow("bad span state")
+ }
+ mHeap_FreeStack(&mheap_, s)
+ }
+}
+
+var maxstacksize uintptr = 1 << 20 // enough until runtime.main sets it for real
+
+var mapnames = []string{
+ _BitsDead: "---",
+ _BitsScalar: "scalar",
+ _BitsPointer: "ptr",
+}
+
+// Stack frame layout
+//
+// (x86)
+// +------------------+
+// | args from caller |
+// +------------------+ <- frame->argp
+// | return address |
+// +------------------+ <- frame->varp
+// | locals |
+// +------------------+
+// | args to callee |
+// +------------------+ <- frame->sp
+//
+// (arm)
+// +------------------+
+// | args from caller |
+// +------------------+ <- frame->argp
+// | caller's retaddr |
+// +------------------+ <- frame->varp
+// | locals |
+// +------------------+
+// | args to callee |
+// +------------------+
+// | return address |
+// +------------------+ <- frame->sp
+
+type adjustinfo struct {
+ old stack
+ delta uintptr // ptr distance from old to new stack (newbase - oldbase)
+}
+
+// Adjustpointer checks whether *vpp is in the old stack described by adjinfo.
+// If so, it rewrites *vpp to point into the new stack.
+func adjustpointer(adjinfo *adjustinfo, vpp unsafe.Pointer) {
+ pp := (*unsafe.Pointer)(vpp)
+ p := *pp
+ if stackDebug >= 4 {
+ print(" ", pp, ":", p, "\n")
+ }
+ if adjinfo.old.lo <= uintptr(p) && uintptr(p) < adjinfo.old.hi {
+ *pp = add(p, adjinfo.delta)
+ if stackDebug >= 3 {
+ print(" adjust ptr ", pp, ":", p, " -> ", *pp, "\n")
+ }
+ }
+}
+
+type gobitvector struct {
+ n uintptr
+ bytedata []uint8
+}
+
+func gobv(bv bitvector) gobitvector {
+ return gobitvector{
+ uintptr(bv.n),
+ (*[1 << 30]byte)(unsafe.Pointer(bv.bytedata))[:(bv.n+7)/8],
+ }
+}
+
+func ptrbits(bv *gobitvector, i uintptr) uint8 {
+ return (bv.bytedata[i/4] >> ((i & 3) * 2)) & 3
+}
+
+// bv describes the memory starting at address scanp.
+// Adjust any pointers contained therein.
+func adjustpointers(scanp unsafe.Pointer, cbv *bitvector, adjinfo *adjustinfo, f *_func) {
+ bv := gobv(*cbv)
+ minp := adjinfo.old.lo
+ maxp := adjinfo.old.hi
+ delta := adjinfo.delta
+ num := uintptr(bv.n / _BitsPerPointer)
+ for i := uintptr(0); i < num; i++ {
+ if stackDebug >= 4 {
+ print(" ", add(scanp, i*ptrSize), ":", mapnames[ptrbits(&bv, i)], ":", hex(*(*uintptr)(add(scanp, i*ptrSize))), " # ", i, " ", bv.bytedata[i/4], "\n")
+ }
+ switch ptrbits(&bv, i) {
+ default:
+ gothrow("unexpected pointer bits")
+ case _BitsDead:
+ if debug.gcdead != 0 {
+ *(*unsafe.Pointer)(add(scanp, i*ptrSize)) = unsafe.Pointer(uintptr(poisonStack))
+ }
+ case _BitsScalar:
+ // ok
+ case _BitsPointer:
+ p := *(*unsafe.Pointer)(add(scanp, i*ptrSize))
+ up := uintptr(p)
+ if f != nil && 0 < up && up < _PageSize && invalidptr != 0 || up == poisonGC || up == poisonStack {
+ // Looks like a junk value in a pointer slot.
+ // Live analysis wrong?
+ getg().m.traceback = 2
+ print("runtime: bad pointer in frame ", gofuncname(f), " at ", add(scanp, i*ptrSize), ": ", p, "\n")
+ gothrow("invalid stack pointer")
+ }
+ if minp <= up && up < maxp {
+ if stackDebug >= 3 {
+ print("adjust ptr ", p, " ", gofuncname(f), "\n")
+ }
+ *(*unsafe.Pointer)(add(scanp, i*ptrSize)) = unsafe.Pointer(up + delta)
+ }
+ }
+ }
+}
+
+// Note: the argument/return area is adjusted by the callee.
+func adjustframe(frame *stkframe, arg unsafe.Pointer) bool {
+ adjinfo := (*adjustinfo)(arg)
+ targetpc := frame.continpc
+ if targetpc == 0 {
+ // Frame is dead.
+ return true
+ }
+ f := frame.fn
+ if stackDebug >= 2 {
+ print(" adjusting ", funcname(f), " frame=[", hex(frame.sp), ",", hex(frame.fp), "] pc=", hex(frame.pc), " continpc=", hex(frame.continpc), "\n")
+ }
+ if f.entry == systemstack_switchPC {
+ // A special routine at the bottom of stack of a goroutine that does an systemstack call.
+ // We will allow it to be copied even though we don't
+ // have full GC info for it (because it is written in asm).
+ return true
+ }
+ if targetpc != f.entry {
+ targetpc--
+ }
+ pcdata := pcdatavalue(f, _PCDATA_StackMapIndex, targetpc)
+ if pcdata == -1 {
+ pcdata = 0 // in prologue
+ }
+
+ // Adjust local variables if stack frame has been allocated.
+ size := frame.varp - frame.sp
+ var minsize uintptr
+ if thechar != '6' && thechar != '8' {
+ minsize = ptrSize
+ } else {
+ minsize = 0
+ }
+ if size > minsize {
+ var bv bitvector
+ stackmap := (*stackmap)(funcdata(f, _FUNCDATA_LocalsPointerMaps))
+ if stackmap == nil || stackmap.n <= 0 {
+ print("runtime: frame ", funcname(f), " untyped locals ", hex(frame.varp-size), "+", hex(size), "\n")
+ gothrow("missing stackmap")
+ }
+ // Locals bitmap information, scan just the pointers in locals.
+ if pcdata < 0 || pcdata >= stackmap.n {
+ // don't know where we are
+ print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " locals stack map entries for ", funcname(f), " (targetpc=", targetpc, ")\n")
+ gothrow("bad symbol table")
+ }
+ bv = stackmapdata(stackmap, pcdata)
+ size = (uintptr(bv.n) * ptrSize) / _BitsPerPointer
+ if stackDebug >= 3 {
+ print(" locals ", pcdata, "/", stackmap.n, " ", size/ptrSize, " words ", bv.bytedata, "\n")
+ }
+ adjustpointers(unsafe.Pointer(frame.varp-size), &bv, adjinfo, f)
+ }
+
+ // Adjust arguments.
+ if frame.arglen > 0 {
+ var bv bitvector
+ if frame.argmap != nil {
+ bv = *frame.argmap
+ } else {
+ stackmap := (*stackmap)(funcdata(f, _FUNCDATA_ArgsPointerMaps))
+ if stackmap == nil || stackmap.n <= 0 {
+ print("runtime: frame ", funcname(f), " untyped args ", frame.argp, "+", uintptr(frame.arglen), "\n")
+ gothrow("missing stackmap")
+ }
+ if pcdata < 0 || pcdata >= stackmap.n {
+ // don't know where we are
+ print("runtime: pcdata is ", pcdata, " and ", stackmap.n, " args stack map entries for ", funcname(f), " (targetpc=", targetpc, ")\n")
+ gothrow("bad symbol table")
+ }
+ bv = stackmapdata(stackmap, pcdata)
+ }
+ if stackDebug >= 3 {
+ print(" args\n")
+ }
+ adjustpointers(unsafe.Pointer(frame.argp), &bv, adjinfo, nil)
+ }
+ return true
+}
+
+func adjustctxt(gp *g, adjinfo *adjustinfo) {
+ adjustpointer(adjinfo, (unsafe.Pointer)(&gp.sched.ctxt))
+}
+
+func adjustdefers(gp *g, adjinfo *adjustinfo) {
+ // Adjust defer argument blocks the same way we adjust active stack frames.
+ tracebackdefers(gp, adjustframe, noescape(unsafe.Pointer(adjinfo)))
+
+ // Adjust pointers in the Defer structs.
+ // Defer structs themselves are never on the stack.
+ for d := gp._defer; d != nil; d = d.link {
+ adjustpointer(adjinfo, (unsafe.Pointer)(&d.fn))
+ adjustpointer(adjinfo, (unsafe.Pointer)(&d.argp))
+ adjustpointer(adjinfo, (unsafe.Pointer)(&d._panic))
+ }
+}
+
+func adjustpanics(gp *g, adjinfo *adjustinfo) {
+ // Panics are on stack and already adjusted.
+ // Update pointer to head of list in G.
+ adjustpointer(adjinfo, (unsafe.Pointer)(&gp._panic))
+}
+
+func adjustsudogs(gp *g, adjinfo *adjustinfo) {
+ // the data elements pointed to by a SudoG structure
+ // might be in the stack.
+ for s := gp.waiting; s != nil; s = s.waitlink {
+ adjustpointer(adjinfo, (unsafe.Pointer)(&s.elem))
+ adjustpointer(adjinfo, (unsafe.Pointer)(&s.selectdone))
+ }
+}
+
+func fillstack(stk stack, b byte) {
+ for p := stk.lo; p < stk.hi; p++ {
+ *(*byte)(unsafe.Pointer(p)) = b
+ }
+}
+
+// Copies gp's stack to a new stack of a different size.
+// Caller must have changed gp status to Gcopystack.
+func copystack(gp *g, newsize uintptr) {
+ if gp.syscallsp != 0 {
+ gothrow("stack growth not allowed in system call")
+ }
+ old := gp.stack
+ if old.lo == 0 {
+ gothrow("nil stackbase")
+ }
+ used := old.hi - gp.sched.sp
+
+ // allocate new stack
+ new := stackalloc(uint32(newsize))
+ if stackPoisonCopy != 0 {
+ fillstack(new, 0xfd)
+ }
+ if stackDebug >= 1 {
+ print("copystack gp=", gp, " [", hex(old.lo), " ", hex(old.hi-used), " ", hex(old.hi), "]/", old.hi-old.lo, " -> [", hex(new.lo), " ", hex(new.hi-used), " ", hex(new.hi), "]/", newsize, "\n")
+ }
+
+ // adjust pointers in the to-be-copied frames
+ var adjinfo adjustinfo
+ adjinfo.old = old
+ adjinfo.delta = new.hi - old.hi
+ gentraceback(^uintptr(0), ^uintptr(0), 0, gp, 0, nil, 0x7fffffff, adjustframe, noescape(unsafe.Pointer(&adjinfo)), 0)
+
+ // adjust other miscellaneous things that have pointers into stacks.
+ adjustctxt(gp, &adjinfo)
+ adjustdefers(gp, &adjinfo)
+ adjustpanics(gp, &adjinfo)
+ adjustsudogs(gp, &adjinfo)
+
+ // copy the stack to the new location
+ if stackPoisonCopy != 0 {
+ fillstack(new, 0xfb)
+ }
+ memmove(unsafe.Pointer(new.hi-used), unsafe.Pointer(old.hi-used), used)
+
+ // Swap out old stack for new one
+ gp.stack = new
+ gp.stackguard0 = new.lo + _StackGuard // NOTE: might clobber a preempt request
+ gp.sched.sp = new.hi - used
+
+ // free old stack
+ if stackPoisonCopy != 0 {
+ fillstack(old, 0xfc)
+ }
+ if newsize > old.hi-old.lo {
+ // growing, free stack immediately
+ stackfree(old)
+ } else {
+ // shrinking, queue up free operation. We can't actually free the stack
+ // just yet because we might run into the following situation:
+ // 1) GC starts, scans a SudoG but does not yet mark the SudoG.elem pointer
+ // 2) The stack that pointer points to is shrunk
+ // 3) The old stack is freed
+ // 4) The containing span is marked free
+ // 5) GC attempts to mark the SudoG.elem pointer. The marking fails because
+ // the pointer looks like a pointer into a free span.
+ // By not freeing, we prevent step #4 until GC is done.
+ lock(&stackpoolmu)
+ *(*stack)(unsafe.Pointer(old.lo)) = stackfreequeue
+ stackfreequeue = old
+ unlock(&stackpoolmu)
+ }
+}
+
+// round x up to a power of 2.
+func round2(x int32) int32 {
+ s := uint(0)
+ for 1<<s < x {
+ s++
+ }
+ return 1 << s
+}
+
+// Called from runtime·morestack when more stack is needed.
+// Allocate larger stack and relocate to new stack.
+// Stack growth is multiplicative, for constant amortized cost.
+//
+// g->atomicstatus will be Grunning or Gscanrunning upon entry.
+// If the GC is trying to stop this g then it will set preemptscan to true.
+func newstack() {
+ thisg := getg()
+ // TODO: double check all gp. shouldn't be getg().
+ if thisg.m.morebuf.g.stackguard0 == stackFork {
+ gothrow("stack growth after fork")
+ }
+ if thisg.m.morebuf.g != thisg.m.curg {
+ print("runtime: newstack called from g=", thisg.m.morebuf.g, "\n"+"\tm=", thisg.m, " m->curg=", thisg.m.curg, " m->g0=", thisg.m.g0, " m->gsignal=", thisg.m.gsignal, "\n")
+ morebuf := thisg.m.morebuf
+ traceback(morebuf.pc, morebuf.sp, morebuf.lr, morebuf.g)
+ gothrow("runtime: wrong goroutine in newstack")
+ }
+ if thisg.m.curg.throwsplit {
+ gp := thisg.m.curg
+ // Update syscallsp, syscallpc in case traceback uses them.
+ morebuf := thisg.m.morebuf
+ gp.syscallsp = morebuf.sp
+ gp.syscallpc = morebuf.pc
+ print("runtime: newstack sp=", hex(gp.sched.sp), " stack=[", hex(gp.stack.lo), ", ", hex(gp.stack.hi), "]\n",
+ "\tmorebuf={pc:", hex(morebuf.pc), " sp:", hex(morebuf.sp), " lr:", hex(morebuf.lr), "}\n",
+ "\tsched={pc:", hex(gp.sched.pc), " sp:", hex(gp.sched.sp), " lr:", hex(gp.sched.lr), " ctxt:", gp.sched.ctxt, "}\n")
+ gothrow("runtime: stack split at bad time")
+ }
+
+ // The goroutine must be executing in order to call newstack,
+ // so it must be Grunning or Gscanrunning.
+
+ gp := thisg.m.curg
+ morebuf := thisg.m.morebuf
+ thisg.m.morebuf.pc = 0
+ thisg.m.morebuf.lr = 0
+ thisg.m.morebuf.sp = 0
+ thisg.m.morebuf.g = nil
+
+ casgstatus(gp, _Grunning, _Gwaiting)
+ gp.waitreason = "stack growth"
+
+ rewindmorestack(&gp.sched)
+
+ if gp.stack.lo == 0 {
+ gothrow("missing stack in newstack")
+ }
+ sp := gp.sched.sp
+ if thechar == '6' || thechar == '8' {
+ // The call to morestack cost a word.
+ sp -= ptrSize
+ }
+ if stackDebug >= 1 || sp < gp.stack.lo {
+ print("runtime: newstack sp=", hex(sp), " stack=[", hex(gp.stack.lo), ", ", hex(gp.stack.hi), "]\n",
+ "\tmorebuf={pc:", hex(morebuf.pc), " sp:", hex(morebuf.sp), " lr:", hex(morebuf.lr), "}\n",
+ "\tsched={pc:", hex(gp.sched.pc), " sp:", hex(gp.sched.sp), " lr:", hex(gp.sched.lr), " ctxt:", gp.sched.ctxt, "}\n")
+ }
+ if sp < gp.stack.lo {
+ print("runtime: gp=", gp, ", gp->status=", hex(readgstatus(gp)), "\n ")
+ print("runtime: split stack overflow: ", hex(sp), " < ", hex(gp.stack.lo), "\n")
+ gothrow("runtime: split stack overflow")
+ }
+
+ if gp.sched.ctxt != nil {
+ // morestack wrote sched.ctxt on its way in here,
+ // without a write barrier. Run the write barrier now.
+ // It is not possible to be preempted between then
+ // and now, so it's okay.
+ writebarrierptr_nostore((*uintptr)(unsafe.Pointer(&gp.sched.ctxt)), uintptr(gp.sched.ctxt))
+ }
+
+ if gp.stackguard0 == stackPreempt {
+ if gp == thisg.m.g0 {
+ gothrow("runtime: preempt g0")
+ }
+ if thisg.m.p == nil && thisg.m.locks == 0 {
+ gothrow("runtime: g is running but p is not")
+ }
+ if gp.preemptscan {
+ gcphasework(gp)
+ casgstatus(gp, _Gwaiting, _Grunning)
+ gp.stackguard0 = gp.stack.lo + _StackGuard
+ gp.preempt = false
+ gp.preemptscan = false // Tells the GC premption was successful.
+ gogo(&gp.sched) // never return
+ }
+
+ // Be conservative about where we preempt.
+ // We are interested in preempting user Go code, not runtime code.
+ if thisg.m.locks != 0 || thisg.m.mallocing != 0 || thisg.m.gcing != 0 || thisg.m.p.status != _Prunning {
+ // Let the goroutine keep running for now.
+ // gp->preempt is set, so it will be preempted next time.
+ gp.stackguard0 = gp.stack.lo + _StackGuard
+ casgstatus(gp, _Gwaiting, _Grunning)
+ gogo(&gp.sched) // never return
+ }
+
+ // Act like goroutine called runtime.Gosched.
+ casgstatus(gp, _Gwaiting, _Grunning)
+ gosched_m(gp) // never return
+ }
+
+ // Allocate a bigger segment and move the stack.
+ oldsize := int(gp.stack.hi - gp.stack.lo)
+ newsize := oldsize * 2
+ if uintptr(newsize) > maxstacksize {
+ print("runtime: goroutine stack exceeds ", maxstacksize, "-byte limit\n")
+ gothrow("stack overflow")
+ }
+
+ oldstatus := readgstatus(gp)
+ oldstatus &^= _Gscan
+ casgstatus(gp, oldstatus, _Gcopystack) // oldstatus is Gwaiting or Grunnable
+
+ // The concurrent GC will not scan the stack while we are doing the copy since
+ // the gp is in a Gcopystack status.
+ copystack(gp, uintptr(newsize))
+ if stackDebug >= 1 {
+ print("stack grow done\n")
+ }
+ casgstatus(gp, _Gcopystack, _Grunning)
+ gogo(&gp.sched)
+}
+
+//go:nosplit
+func nilfunc() {
+ *(*uint8)(nil) = 0
+}
+
+// adjust Gobuf as if it executed a call to fn
+// and then did an immediate gosave.
+func gostartcallfn(gobuf *gobuf, fv *funcval) {
+ var fn unsafe.Pointer
+ if fv != nil {
+ fn = (unsafe.Pointer)(fv.fn)
+ } else {
+ fn = unsafe.Pointer(funcPC(nilfunc))
+ }
+ gostartcall(gobuf, fn, (unsafe.Pointer)(fv))
+}
+
+// Maybe shrink the stack being used by gp.
+// Called at garbage collection time.
+func shrinkstack(gp *g) {
+ if readgstatus(gp) == _Gdead {
+ if gp.stack.lo != 0 {
+ // Free whole stack - it will get reallocated
+ // if G is used again.
+ stackfree(gp.stack)
+ gp.stack.lo = 0
+ gp.stack.hi = 0
+ }
+ return
+ }
+ if gp.stack.lo == 0 {
+ gothrow("missing stack in shrinkstack")
+ }
+
+ oldsize := gp.stack.hi - gp.stack.lo
+ newsize := oldsize / 2
+ if newsize < _FixedStack {
+ return // don't shrink below the minimum-sized stack
+ }
+ used := gp.stack.hi - gp.sched.sp
+ if used >= oldsize/4 {
+ return // still using at least 1/4 of the segment.
+ }
+
+ // We can't copy the stack if we're in a syscall.
+ // The syscall might have pointers into the stack.
+ if gp.syscallsp != 0 {
+ return
+ }
+ if _Windows != 0 && gp.m != nil && gp.m.libcallsp != 0 {
+ return
+ }
+
+ if stackDebug > 0 {
+ print("shrinking stack ", oldsize, "->", newsize, "\n")
+ }
+
+ // This is being done in a Gscan state and was initiated by the GC so no need to move to
+ // the Gcopystate.
+ // The world is stopped, so the goroutine must be Gwaiting or Grunnable,
+ // and what it is is not changing underfoot.
+ oldstatus := readgstatus(gp) &^ _Gscan
+ if oldstatus != _Gwaiting && oldstatus != _Grunnable {
+ gothrow("status is not Gwaiting or Grunnable")
+ }
+ casgstatus(gp, oldstatus, _Gcopystack)
+ copystack(gp, newsize)
+ casgstatus(gp, _Gcopystack, oldstatus)
+}
+
+// Do any delayed stack freeing that was queued up during GC.
+func shrinkfinish() {
+ lock(&stackpoolmu)
+ s := stackfreequeue
+ stackfreequeue = stack{}
+ unlock(&stackpoolmu)
+ for s.lo != 0 {
+ t := *(*stack)(unsafe.Pointer(s.lo))
+ stackfree(s)
+ s = t
+ }
+}
+
+//go:nosplit
+func morestackc() {
+ systemstack(func() {
+ gothrow("attempt to execute C code on Go stack")
+ })
+}
