diff --git a/src/cmd/compile/internal/gc/esc.go b/src/cmd/compile/internal/gc/esc.go index ded9439a14..c42f25e104 100644 --- a/src/cmd/compile/internal/gc/esc.go +++ b/src/cmd/compile/internal/gc/esc.go @@ -802,6 +802,7 @@ opSwitch: case ODEFER: if e.loopdepth == 1 { // top level + n.Esc = EscNever // force stack allocation of defer record (see ssa.go) break } // arguments leak out of scope diff --git a/src/cmd/compile/internal/gc/escape.go b/src/cmd/compile/internal/gc/escape.go index 88dc9ef8a8..47ce853858 100644 --- a/src/cmd/compile/internal/gc/escape.go +++ b/src/cmd/compile/internal/gc/escape.go @@ -882,6 +882,7 @@ func (e *Escape) augmentParamHole(k EscHole, where *Node) EscHole { // non-transient location to avoid arguments from being // transiently allocated. if where.Op == ODEFER && e.loopDepth == 1 { + where.Esc = EscNever // force stack allocation of defer record (see ssa.go) // TODO(mdempsky): Eliminate redundant EscLocation allocs. return e.teeHole(k, e.newLoc(nil, false).asHole()) } diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go index a776af9f66..f36e2716d6 100644 --- a/src/cmd/compile/internal/gc/go.go +++ b/src/cmd/compile/internal/gc/go.go @@ -291,6 +291,7 @@ var ( assertI2I, assertI2I2, deferproc, + deferprocStack, Deferreturn, Duffcopy, Duffzero, diff --git a/src/cmd/compile/internal/gc/reflect.go b/src/cmd/compile/internal/gc/reflect.go index 04707b9ad2..0854817713 100644 --- a/src/cmd/compile/internal/gc/reflect.go +++ b/src/cmd/compile/internal/gc/reflect.go @@ -317,6 +317,48 @@ func hiter(t *types.Type) *types.Type { return hiter } +// deferstruct makes a runtime._defer structure, with additional space for +// stksize bytes of args. +func deferstruct(stksize int64) *types.Type { + makefield := func(name string, typ *types.Type) *types.Field { + f := types.NewField() + f.Type = typ + // Unlike the global makefield function, this one needs to set Pkg + // because these types might be compared (in SSA CSE sorting). + // TODO: unify this makefield and the global one above. + f.Sym = &types.Sym{Name: name, Pkg: localpkg} + return f + } + argtype := types.NewArray(types.Types[TUINT8], stksize) + argtype.SetNoalg(true) + argtype.Width = stksize + argtype.Align = 1 + // These fields must match the ones in runtime/runtime2.go:_defer and + // cmd/compile/internal/gc/ssa.go:(*state).call. + fields := []*types.Field{ + makefield("siz", types.Types[TUINT32]), + makefield("started", types.Types[TBOOL]), + makefield("heap", types.Types[TBOOL]), + makefield("sp", types.Types[TUINTPTR]), + makefield("pc", types.Types[TUINTPTR]), + // Note: the types here don't really matter. Defer structures + // are always scanned explicitly during stack copying and GC, + // so we make them uintptr type even though they are real pointers. + makefield("fn", types.Types[TUINTPTR]), + makefield("_panic", types.Types[TUINTPTR]), + makefield("link", types.Types[TUINTPTR]), + makefield("args", argtype), + } + + // build struct holding the above fields + s := types.New(TSTRUCT) + s.SetNoalg(true) + s.SetFields(fields) + s.Width = widstruct(s, s, 0, 1) + s.Align = uint8(Widthptr) + return s +} + // f is method type, with receiver. // return function type, receiver as first argument (or not). func methodfunc(f *types.Type, receiver *types.Type) *types.Type { diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go index 4c9bcfe2a5..5509e3d182 100644 --- a/src/cmd/compile/internal/gc/ssa.go +++ b/src/cmd/compile/internal/gc/ssa.go @@ -68,6 +68,7 @@ func initssaconfig() { assertI2I = sysfunc("assertI2I") assertI2I2 = sysfunc("assertI2I2") deferproc = sysfunc("deferproc") + deferprocStack = sysfunc("deferprocStack") Deferreturn = sysfunc("deferreturn") Duffcopy = sysvar("duffcopy") // asm func with special ABI Duffzero = sysvar("duffzero") // asm func with special ABI @@ -864,7 +865,11 @@ func (s *state) stmt(n *Node) { } } case ODEFER: - s.call(n.Left, callDefer) + d := callDefer + if n.Esc == EscNever { + d = callDeferStack + } + s.call(n.Left, d) case OGO: s.call(n.Left, callGo) @@ -2859,6 +2864,7 @@ type callKind int8 const ( callNormal callKind = iota callDefer + callDeferStack callGo ) @@ -3799,74 +3805,132 @@ func (s *state) call(n *Node, k callKind) *ssa.Value { rcvr = s.newValue1(ssa.OpIData, types.Types[TUINTPTR], i) } dowidth(fn.Type) - stksize := fn.Type.ArgWidth() // includes receiver + stksize := fn.Type.ArgWidth() // includes receiver, args, and results // Run all assignments of temps. // The temps are introduced to avoid overwriting argument // slots when arguments themselves require function calls. s.stmtList(n.List) - // Store arguments to stack, including defer/go arguments and receiver for method calls. - // These are written in SP-offset order. - argStart := Ctxt.FixedFrameSize() - // Defer/go args. - if k != callNormal { - // Write argsize and closure (args to newproc/deferproc). - argsize := s.constInt32(types.Types[TUINT32], int32(stksize)) - addr := s.constOffPtrSP(s.f.Config.Types.UInt32Ptr, argStart) - s.store(types.Types[TUINT32], addr, argsize) - addr = s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart+int64(Widthptr)) - s.store(types.Types[TUINTPTR], addr, closure) - stksize += 2 * int64(Widthptr) - argStart += 2 * int64(Widthptr) - } - - // Set receiver (for interface calls). - if rcvr != nil { - addr := s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart) - s.store(types.Types[TUINTPTR], addr, rcvr) - } - - // Write args. - t := n.Left.Type - args := n.Rlist.Slice() - if n.Op == OCALLMETH { - f := t.Recv() - s.storeArg(args[0], f.Type, argStart+f.Offset) - args = args[1:] - } - for i, n := range args { - f := t.Params().Field(i) - s.storeArg(n, f.Type, argStart+f.Offset) - } - - // call target var call *ssa.Value - switch { - case k == callDefer: - call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferproc, s.mem()) - case k == callGo: - call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, newproc, s.mem()) - case closure != nil: - // rawLoad because loading the code pointer from a - // closure is always safe, but IsSanitizerSafeAddr - // can't always figure that out currently, and it's - // critical that we not clobber any arguments already - // stored onto the stack. - codeptr = s.rawLoad(types.Types[TUINTPTR], closure) - call = s.newValue3(ssa.OpClosureCall, types.TypeMem, codeptr, closure, s.mem()) - case codeptr != nil: - call = s.newValue2(ssa.OpInterCall, types.TypeMem, codeptr, s.mem()) - case sym != nil: - call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, sym.Linksym(), s.mem()) - default: - Fatalf("bad call type %v %v", n.Op, n) + if k == callDeferStack { + // Make a defer struct d on the stack. + t := deferstruct(stksize) + d := tempAt(n.Pos, s.curfn, t) + + s.vars[&memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, d, s.mem()) + addr := s.addr(d, false) + + // Must match reflect.go:deferstruct and src/runtime/runtime2.go:_defer. + // 0: siz + s.store(types.Types[TUINT32], + s.newValue1I(ssa.OpOffPtr, types.Types[TUINT32].PtrTo(), t.FieldOff(0), addr), + s.constInt32(types.Types[TUINT32], int32(stksize))) + // 1: started, set in deferprocStack + // 2: heap, set in deferprocStack + // 3: sp, set in deferprocStack + // 4: pc, set in deferprocStack + // 5: fn + s.store(closure.Type, + s.newValue1I(ssa.OpOffPtr, closure.Type.PtrTo(), t.FieldOff(5), addr), + closure) + // 6: panic, set in deferprocStack + // 7: link, set in deferprocStack + + // Then, store all the arguments of the defer call. + ft := fn.Type + off := t.FieldOff(8) + args := n.Rlist.Slice() + + // Set receiver (for interface calls). Always a pointer. + if rcvr != nil { + p := s.newValue1I(ssa.OpOffPtr, ft.Recv().Type.PtrTo(), off, addr) + s.store(types.Types[TUINTPTR], p, rcvr) + } + // Set receiver (for method calls). + if n.Op == OCALLMETH { + f := ft.Recv() + s.storeArgWithBase(args[0], f.Type, addr, off+f.Offset) + args = args[1:] + } + // Set other args. + for _, f := range ft.Params().Fields().Slice() { + s.storeArgWithBase(args[0], f.Type, addr, off+f.Offset) + args = args[1:] + } + + // Call runtime.deferprocStack with pointer to _defer record. + arg0 := s.constOffPtrSP(types.Types[TUINTPTR], Ctxt.FixedFrameSize()) + s.store(types.Types[TUINTPTR], arg0, addr) + call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferprocStack, s.mem()) + if stksize < int64(Widthptr) { + // We need room for both the call to deferprocStack and the call to + // the deferred function. + stksize = int64(Widthptr) + } + call.AuxInt = stksize + } else { + // Store arguments to stack, including defer/go arguments and receiver for method calls. + // These are written in SP-offset order. + argStart := Ctxt.FixedFrameSize() + // Defer/go args. + if k != callNormal { + // Write argsize and closure (args to newproc/deferproc). + argsize := s.constInt32(types.Types[TUINT32], int32(stksize)) + addr := s.constOffPtrSP(s.f.Config.Types.UInt32Ptr, argStart) + s.store(types.Types[TUINT32], addr, argsize) + addr = s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart+int64(Widthptr)) + s.store(types.Types[TUINTPTR], addr, closure) + stksize += 2 * int64(Widthptr) + argStart += 2 * int64(Widthptr) + } + + // Set receiver (for interface calls). + if rcvr != nil { + addr := s.constOffPtrSP(s.f.Config.Types.UintptrPtr, argStart) + s.store(types.Types[TUINTPTR], addr, rcvr) + } + + // Write args. + t := n.Left.Type + args := n.Rlist.Slice() + if n.Op == OCALLMETH { + f := t.Recv() + s.storeArg(args[0], f.Type, argStart+f.Offset) + args = args[1:] + } + for i, n := range args { + f := t.Params().Field(i) + s.storeArg(n, f.Type, argStart+f.Offset) + } + + // call target + switch { + case k == callDefer: + call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, deferproc, s.mem()) + case k == callGo: + call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, newproc, s.mem()) + case closure != nil: + // rawLoad because loading the code pointer from a + // closure is always safe, but IsSanitizerSafeAddr + // can't always figure that out currently, and it's + // critical that we not clobber any arguments already + // stored onto the stack. + codeptr = s.rawLoad(types.Types[TUINTPTR], closure) + call = s.newValue3(ssa.OpClosureCall, types.TypeMem, codeptr, closure, s.mem()) + case codeptr != nil: + call = s.newValue2(ssa.OpInterCall, types.TypeMem, codeptr, s.mem()) + case sym != nil: + call = s.newValue1A(ssa.OpStaticCall, types.TypeMem, sym.Linksym(), s.mem()) + default: + Fatalf("bad call type %v %v", n.Op, n) + } + call.AuxInt = stksize // Call operations carry the argsize of the callee along with them } - call.AuxInt = stksize // Call operations carry the argsize of the callee along with them s.vars[&memVar] = call // Finish block for defers - if k == callDefer { + if k == callDefer || k == callDeferStack { b := s.endBlock() b.Kind = ssa.BlockDefer b.SetControl(call) @@ -4361,17 +4425,27 @@ func (s *state) storeTypePtrs(t *types.Type, left, right *ssa.Value) { } func (s *state) storeArg(n *Node, t *types.Type, off int64) { + s.storeArgWithBase(n, t, s.sp, off) +} + +func (s *state) storeArgWithBase(n *Node, t *types.Type, base *ssa.Value, off int64) { pt := types.NewPtr(t) - sp := s.constOffPtrSP(pt, off) + var addr *ssa.Value + if base == s.sp { + // Use special routine that avoids allocation on duplicate offsets. + addr = s.constOffPtrSP(pt, off) + } else { + addr = s.newValue1I(ssa.OpOffPtr, pt, off, base) + } if !canSSAType(t) { a := s.addr(n, false) - s.move(t, sp, a) + s.move(t, addr, a) return } a := s.expr(n) - s.storeType(t, sp, a, 0, false) + s.storeType(t, addr, a, 0, false) } // slice computes the slice v[i:j:k] and returns ptr, len, and cap of result. diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go index efa007aa97..2c63724472 100644 --- a/src/runtime/mgcmark.go +++ b/src/runtime/mgcmark.go @@ -712,15 +712,31 @@ func scanstack(gp *g, gcw *gcWork) { // Find additional pointers that point into the stack from the heap. // Currently this includes defers and panics. See also function copystack. + + // Find and trace all defer arguments. tracebackdefers(gp, scanframe, nil) + + // Find and trace other pointers in defer records. for d := gp._defer; d != nil; d = d.link { - // tracebackdefers above does not scan the func value, which could - // be a stack allocated closure. See issue 30453. if d.fn != nil { + // tracebackdefers above does not scan the func value, which could + // be a stack allocated closure. See issue 30453. scanblock(uintptr(unsafe.Pointer(&d.fn)), sys.PtrSize, &oneptrmask[0], gcw, &state) } + if d.link != nil { + // The link field of a stack-allocated defer record might point + // to a heap-allocated defer record. Keep that heap record live. + scanblock(uintptr(unsafe.Pointer(&d.link)), sys.PtrSize, &oneptrmask[0], gcw, &state) + } + // Retain defers records themselves. + // Defer records might not be reachable from the G through regular heap + // tracing because the defer linked list might weave between the stack and the heap. + if d.heap { + scanblock(uintptr(unsafe.Pointer(&d)), sys.PtrSize, &oneptrmask[0], gcw, &state) + } } if gp._panic != nil { + // Panics are always stack allocated. state.putPtr(uintptr(unsafe.Pointer(gp._panic))) } diff --git a/src/runtime/panic.go b/src/runtime/panic.go index f39a4bc0a2..ce26eb540d 100644 --- a/src/runtime/panic.go +++ b/src/runtime/panic.go @@ -228,6 +228,46 @@ func deferproc(siz int32, fn *funcval) { // arguments of fn follow fn // been set and must not be clobbered. } +// deferprocStack queues a new deferred function with a defer record on the stack. +// The defer record must have its siz and fn fields initialized. +// All other fields can contain junk. +// The defer record must be immediately followed in memory by +// the arguments of the defer. +// Nosplit because the arguments on the stack won't be scanned +// until the defer record is spliced into the gp._defer list. +//go:nosplit +func deferprocStack(d *_defer) { + gp := getg() + if gp.m.curg != gp { + // go code on the system stack can't defer + throw("defer on system stack") + } + // siz and fn are already set. + // The other fields are junk on entry to deferprocStack and + // are initialized here. + d.started = false + d.heap = false + d.sp = getcallersp() + d.pc = getcallerpc() + // The lines below implement: + // d.panic = nil + // d.link = gp._defer + // gp._defer = d + // But without write barriers. The first two are writes to + // the stack so they don't need a write barrier, and furthermore + // are to uninitialized memory, so they must not use a write barrier. + // The third write does not require a write barrier because we + // explicitly mark all the defer structures, so we don't need to + // keep track of pointers to them with a write barrier. + *(*uintptr)(unsafe.Pointer(&d._panic)) = 0 + *(*uintptr)(unsafe.Pointer(&d.link)) = uintptr(unsafe.Pointer(gp._defer)) + *(*uintptr)(unsafe.Pointer(&gp._defer)) = uintptr(unsafe.Pointer(d)) + + return0() + // No code can go here - the C return register has + // been set and must not be clobbered. +} + // Small malloc size classes >= 16 are the multiples of 16: 16, 32, 48, 64, 80, 96, 112, 128, 144, ... // Each P holds a pool for defers with small arg sizes. // Assign defer allocations to pools by rounding to 16, to match malloc size classes. @@ -349,6 +389,7 @@ func newdefer(siz int32) *_defer { } } d.siz = siz + d.heap = true d.link = gp._defer gp._defer = d return d @@ -368,6 +409,9 @@ func freedefer(d *_defer) { if d.fn != nil { freedeferfn() } + if !d.heap { + return + } sc := deferclass(uintptr(d.siz)) if sc >= uintptr(len(p{}.deferpool)) { return diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go index bc5b48222b..16c02cd1ed 100644 --- a/src/runtime/runtime2.go +++ b/src/runtime/runtime2.go @@ -775,9 +775,16 @@ func extendRandom(r []byte, n int) { // A _defer holds an entry on the list of deferred calls. // If you add a field here, add code to clear it in freedefer. +// This struct must match the code in cmd/compile/internal/gc/reflect.go:deferstruct +// and cmd/compile/internal/gc/ssa.go:(*state).call. +// Some defers will be allocated on the stack and some on the heap. +// All defers are logically part of the stack, so write barriers to +// initialize them are not required. All defers must be manually scanned, +// and for heap defers, marked. type _defer struct { - siz int32 + siz int32 // includes both arguments and results started bool + heap bool sp uintptr // sp at time of defer pc uintptr fn *funcval diff --git a/src/runtime/stack.go b/src/runtime/stack.go index 22a0053fdb..7ae3eeef83 100644 --- a/src/runtime/stack.go +++ b/src/runtime/stack.go @@ -719,16 +719,21 @@ func adjustctxt(gp *g, adjinfo *adjustinfo) { } 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. + // We need to do this first because we need to adjust the + // defer.link fields so we always work on the new stack. + adjustpointer(adjinfo, unsafe.Pointer(&gp._defer)) for d := gp._defer; d != nil; d = d.link { adjustpointer(adjinfo, unsafe.Pointer(&d.fn)) adjustpointer(adjinfo, unsafe.Pointer(&d.sp)) adjustpointer(adjinfo, unsafe.Pointer(&d._panic)) + adjustpointer(adjinfo, unsafe.Pointer(&d.link)) } + + // Adjust defer argument blocks the same way we adjust active stack frames. + // Note: this code is after the loop above, so that if a defer record is + // stack allocated, we work on the copy in the new stack. + tracebackdefers(gp, adjustframe, noescape(unsafe.Pointer(adjinfo))) } func adjustpanics(gp *g, adjinfo *adjustinfo) { diff --git a/src/runtime/stack_test.go b/src/runtime/stack_test.go index df73b3a1d5..143d3a99a0 100644 --- a/src/runtime/stack_test.go +++ b/src/runtime/stack_test.go @@ -799,3 +799,58 @@ func TestDeferLiveness(t *testing.T) { t.Errorf("output:\n%s\n\nwant no output", output) } } + +func TestDeferHeapAndStack(t *testing.T) { + P := 4 // processors + N := 10000 //iterations + D := 200 // stack depth + + if testing.Short() { + P /= 2 + N /= 10 + D /= 10 + } + c := make(chan bool) + for p := 0; p < P; p++ { + go func() { + for i := 0; i < N; i++ { + if deferHeapAndStack(D) != 2*D { + panic("bad result") + } + } + c <- true + }() + } + for p := 0; p < P; p++ { + <-c + } +} + +// deferHeapAndStack(n) computes 2*n +func deferHeapAndStack(n int) (r int) { + if n == 0 { + return 0 + } + if n%2 == 0 { + // heap-allocated defers + for i := 0; i < 2; i++ { + defer func() { + r++ + }() + } + } else { + // stack-allocated defers + defer func() { + r++ + }() + defer func() { + r++ + }() + } + r = deferHeapAndStack(n - 1) + escapeMe(new([1024]byte)) // force some GCs + return +} + +// Pass a value to escapeMe to force it to escape. +var escapeMe = func(x interface{}) {} diff --git a/src/runtime/stubs.go b/src/runtime/stubs.go index 18e64dd5f7..26aaf2224d 100644 --- a/src/runtime/stubs.go +++ b/src/runtime/stubs.go @@ -248,9 +248,6 @@ func getclosureptr() uintptr //go:noescape func asmcgocall(fn, arg unsafe.Pointer) int32 -// argp used in Defer structs when there is no argp. -const _NoArgs = ^uintptr(0) - func morestack() func morestack_noctxt() func rt0_go() diff --git a/src/runtime/syscall_windows.go b/src/runtime/syscall_windows.go index 36ad7511af..722a73d108 100644 --- a/src/runtime/syscall_windows.go +++ b/src/runtime/syscall_windows.go @@ -112,7 +112,6 @@ const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800 //go:nosplit func syscall_loadsystemlibrary(filename *uint16, absoluteFilepath *uint16) (handle, err uintptr) { lockOSThread() - defer unlockOSThread() c := &getg().m.syscall if useLoadLibraryEx { @@ -135,6 +134,7 @@ func syscall_loadsystemlibrary(filename *uint16, absoluteFilepath *uint16) (hand if handle == 0 { err = c.err } + unlockOSThread() // not defer'd after the lockOSThread above to save stack frame size. return } diff --git a/src/runtime/traceback.go b/src/runtime/traceback.go index d817018501..ef48c9fa1f 100644 --- a/src/runtime/traceback.go +++ b/src/runtime/traceback.go @@ -148,11 +148,6 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in waspanic := false cgoCtxt := gp.cgoCtxt printing := pcbuf == nil && callback == nil - _defer := gp._defer - - for _defer != nil && _defer.sp == _NoArgs { - _defer = _defer.link - } // If the PC is zero, it's likely a nil function call. // Start in the caller's frame. @@ -319,15 +314,14 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in // In the latter case, use a deferreturn call site as the continuation pc. frame.continpc = frame.pc if waspanic { - // We match up defers with frames using the SP. - // However, if the function has an empty stack - // frame, then it's possible (on LR machines) - // for multiple call frames to have the same - // SP. But, since a function with no frame - // can't push a defer, the defer can't belong - // to that frame. - if _defer != nil && _defer.sp == frame.sp && frame.sp != frame.fp { + if frame.fn.deferreturn != 0 { frame.continpc = frame.fn.entry + uintptr(frame.fn.deferreturn) + 1 + // Note: this may perhaps keep return variables alive longer than + // strictly necessary, as we are using "function has a defer statement" + // as a proxy for "function actually deferred something". It seems + // to be a minor drawback. (We used to actually look through the + // gp._defer for a defer corresponding to this function, but that + // is hard to do with defer records on the stack during a stack copy.) // Note: the +1 is to offset the -1 that // stack.go:getStackMap does to back up a return // address make sure the pc is in the CALL instruction. @@ -336,11 +330,6 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in } } - // Unwind our local defer stack past this frame. - for _defer != nil && ((_defer.sp == frame.sp && frame.sp != frame.fp) || _defer.sp == _NoArgs) { - _defer = _defer.link - } - if callback != nil { if !callback((*stkframe)(noescape(unsafe.Pointer(&frame))), v) { return n @@ -510,13 +499,6 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in n = nprint } - // If callback != nil, we're being called to gather stack information during - // garbage collection or stack growth. In that context, require that we used - // up the entire defer stack. If not, then there is a bug somewhere and the - // garbage collection or stack growth may not have seen the correct picture - // of the stack. Crash now instead of silently executing the garbage collection - // or stack copy incorrectly and setting up for a mysterious crash later. - // // Note that panic != nil is okay here: there can be leftover panics, // because the defers on the panic stack do not nest in frame order as // they do on the defer stack. If you have: @@ -557,16 +539,6 @@ func gentraceback(pc0, sp0, lr0 uintptr, gp *g, skip int, pcbuf *uintptr, max in // At other times, such as when gathering a stack for a profiling signal // or when printing a traceback during a crash, everything may not be // stopped nicely, and the stack walk may not be able to complete. - // It's okay in those situations not to use up the entire defer stack: - // incomplete information then is still better than nothing. - if callback != nil && n < max && _defer != nil { - print("runtime: g", gp.goid, ": leftover defer sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n") - for _defer = gp._defer; _defer != nil; _defer = _defer.link { - print("\tdefer ", _defer, " sp=", hex(_defer.sp), " pc=", hex(_defer.pc), "\n") - } - throw("traceback has leftover defers") - } - if callback != nil && n < max && frame.sp != gp.stktopsp { print("runtime: g", gp.goid, ": frame.sp=", hex(frame.sp), " top=", hex(gp.stktopsp), "\n") print("\tstack=[", hex(gp.stack.lo), "-", hex(gp.stack.hi), "] n=", n, " max=", max, "\n") diff --git a/test/codegen/stack.go b/test/codegen/stack.go index ca37622286..37d378aa78 100644 --- a/test/codegen/stack.go +++ b/test/codegen/stack.go @@ -109,3 +109,8 @@ func MightPanic(a []int, i, j, k, s int) { _ = i << s // panicShift _ = i / j // panicDivide } + +func Defer() { + // amd64:`CALL\truntime\.deferprocStack` + defer func() {}() +} diff --git a/test/live.go b/test/live.go index e7134eca0c..ec51193725 100644 --- a/test/live.go +++ b/test/live.go @@ -687,7 +687,7 @@ type R struct{ *T } // ERRORAUTO "live at entry to \(\*R\)\.Foo: \.this ptr" "li // In particular, at printint r must be live. func f41(p, q *int) (r *int) { // ERROR "live at entry to f41: p q$" r = p - defer func() { // ERROR "live at call to deferproc: q r$" "live at call to deferreturn: r$" + defer func() { // ERROR "live at call to deferprocStack: q r$" "live at call to deferreturn: r$" recover() }() printint(0) // ERROR "live at call to printint: q r$"