96 lines
2.1 KiB
Go
96 lines
2.1 KiB
Go
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// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"bytes"
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"fmt"
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"runtime"
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"strings"
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)
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func init() {
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register("TracebackAncestors", TracebackAncestors)
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}
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const numGoroutines = 3
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const numFrames = 2
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func TracebackAncestors() {
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w := make(chan struct{})
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recurseThenCallGo(w, numGoroutines, numFrames, true)
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<-w
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printStack()
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close(w)
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}
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var ignoreGoroutines = make(map[string]bool)
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func printStack() {
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buf := make([]byte, 1024)
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for {
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n := runtime.Stack(buf, true)
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if n < len(buf) {
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all := string(buf[:n])
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var saved string
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// Delete any ignored goroutines, if present.
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for all != "" {
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var g string
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g, all, _ = strings.Cut(all, "\n\n")
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if strings.HasPrefix(g, "goroutine ") {
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id, _, _ := strings.Cut(strings.TrimPrefix(g, "goroutine "), " ")
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if ignoreGoroutines[id] {
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continue
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}
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}
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if saved != "" {
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saved += "\n\n"
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}
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saved += g
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}
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fmt.Print(saved)
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return
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}
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buf = make([]byte, 2*len(buf))
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}
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}
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func recurseThenCallGo(w chan struct{}, frames int, goroutines int, main bool) {
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if frames == 0 {
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// Signal to TracebackAncestors that we are done recursing and starting goroutines.
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w <- struct{}{}
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<-w
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return
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}
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if goroutines == 0 {
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// Record which goroutine this is so we can ignore it
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// in the traceback if it hasn't finished exiting by
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// the time we printStack.
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if !main {
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ignoreGoroutines[goroutineID()] = true
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}
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// Start the next goroutine now that there are no more recursions left
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// for this current goroutine.
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go recurseThenCallGo(w, frames-1, numFrames, false)
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return
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}
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recurseThenCallGo(w, frames, goroutines-1, main)
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}
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func goroutineID() string {
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buf := make([]byte, 128)
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runtime.Stack(buf, false)
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prefix := []byte("goroutine ")
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if !bytes.HasPrefix(buf, prefix) {
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panic(fmt.Sprintf("expected %q at beginning of traceback:\n%s", prefix, buf))
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}
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id, _, _ := bytes.Cut(bytes.TrimPrefix(buf, prefix), []byte(" "))
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return string(id)
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}
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