github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/runtime/race/sched_test.go (about)

     1  // Copyright 2015 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  //go:build race
     6  // +build race
     7  
     8  package race_test
     9  
    10  import (
    11  	"bytes"
    12  	"fmt"
    13  	"reflect"
    14  	"runtime"
    15  	"testing"
    16  )
    17  
    18  func TestRandomScheduling(t *testing.T) {
    19  	// Scheduler is most consistent with GOMAXPROCS=1.
    20  	// Use that to make the test most likely to fail.
    21  	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
    22  	const N = 10
    23  	out := make([][]int, N)
    24  	for i := 0; i < N; i++ {
    25  		c := make(chan int, N)
    26  		for j := 0; j < N; j++ {
    27  			go func(j int) {
    28  				c <- j
    29  			}(j)
    30  		}
    31  		row := make([]int, N)
    32  		for j := 0; j < N; j++ {
    33  			row[j] = <-c
    34  		}
    35  		out[i] = row
    36  	}
    37  
    38  	for i := 0; i < N; i++ {
    39  		if !reflect.DeepEqual(out[0], out[i]) {
    40  			return // found a different order
    41  		}
    42  	}
    43  
    44  	var buf bytes.Buffer
    45  	for i := 0; i < N; i++ {
    46  		fmt.Fprintf(&buf, "%v\n", out[i])
    47  	}
    48  	t.Fatalf("consistent goroutine execution order:\n%v", buf.String())
    49  }