traceback_ancestors.go

Documentation: runtime/testdata/testprog

     1  // Copyright 2018 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package main
     6  
     7  import (
     8  	"bytes"
     9  	"fmt"
    10  	"runtime"
    11  	"strings"
    12  )
    13  
    14  func init() {
    15  	register("TracebackAncestors", TracebackAncestors)
    16  }
    17  
    18  const numGoroutines = 3
    19  const numFrames = 2
    20  
    21  func TracebackAncestors() {
    22  	w := make(chan struct{})
    23  	recurseThenCallGo(w, numGoroutines, numFrames, true)
    24  	<-w
    25  	printStack()
    26  	close(w)
    27  }
    28  
    29  var ignoreGoroutines = make(map[string]bool)
    30  
    31  func printStack() {
    32  	buf := make([]byte, 1024)
    33  	for {
    34  		n := runtime.Stack(buf, true)
    35  		if n < len(buf) {
    36  			tb := string(buf[:n])
    37  
    38  			// Delete any ignored goroutines, if present.
    39  			pos := 0
    40  			for pos < len(tb) {
    41  				next := pos + strings.Index(tb[pos:], "\n\n")
    42  				if next < pos {
    43  					next = len(tb)
    44  				} else {
    45  					next += len("\n\n")
    46  				}
    47  
    48  				if strings.HasPrefix(tb[pos:], "goroutine ") {
    49  					id := tb[pos+len("goroutine "):]
    50  					id = id[:strings.IndexByte(id, ' ')]
    51  					if ignoreGoroutines[id] {
    52  						tb = tb[:pos] + tb[next:]
    53  						next = pos
    54  					}
    55  				}
    56  				pos = next
    57  			}
    58  
    59  			fmt.Print(tb)
    60  			return
    61  		}
    62  		buf = make([]byte, 2*len(buf))
    63  	}
    64  }
    65  
    66  func recurseThenCallGo(w chan struct{}, frames int, goroutines int, main bool) {
    67  	if frames == 0 {
    68  		// Signal to TracebackAncestors that we are done recursing and starting goroutines.
    69  		w <- struct{}{}
    70  		<-w
    71  		return
    72  	}
    73  	if goroutines == 0 {
    74  		// Record which goroutine this is so we can ignore it
    75  		// in the traceback if it hasn't finished exiting by
    76  		// the time we printStack.
    77  		if !main {
    78  			ignoreGoroutines[goroutineID()] = true
    79  		}
    80  
    81  		// Start the next goroutine now that there are no more recursions left
    82  		// for this current goroutine.
    83  		go recurseThenCallGo(w, frames-1, numFrames, false)
    84  		return
    85  	}
    86  	recurseThenCallGo(w, frames, goroutines-1, main)
    87  }
    88  
    89  func goroutineID() string {
    90  	buf := make([]byte, 128)
    91  	runtime.Stack(buf, false)
    92  	const prefix = "goroutine "
    93  	if !bytes.HasPrefix(buf, []byte(prefix)) {
    94  		panic(fmt.Sprintf("expected %q at beginning of traceback:\n%s", prefix, buf))
    95  	}
    96  	buf = buf[len(prefix):]
    97  	n := bytes.IndexByte(buf, ' ')
    98  	return string(buf[:n])
    99  }
   100
View as plain text