1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
|
// $G $D/$F.go && $L $F.$A && ./$A.out
// Copyright 2009 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.
// This test is designed to flush out the case where two cases of a select can
// both end up running. See http://codereview.appspot.com/180068.
package main
import (
"flag"
"runtime"
)
var iterations *int = flag.Int("n", 100000, "number of iterations")
// sender sends a counter to one of four different channels. If two
// cases both end up running in the same iteration, the same value will be sent
// to two different channels.
func sender(n int, c1, c2, c3, c4 chan<- int) {
defer close(c1)
defer close(c2)
for i := 0; i < n; i++ {
select {
case c1 <- i:
case c2 <- i:
case c3 <- i:
case c4 <- i:
}
}
}
// mux receives the values from sender and forwards them onto another channel.
// It would be simplier to just have sender's four cases all be the same
// channel, but this doesn't actually trigger the bug.
func mux(out chan<- int, in <-chan int) {
for {
v := <-in
if closed(in) {
close(out)
break
}
out <- v
}
}
// recver gets a steam of values from the four mux's and checks for duplicates.
func recver(in <-chan int) {
seen := make(map[int]bool)
for {
v := <-in
if closed(in) {
break
}
if _, ok := seen[v]; ok {
println("got duplicate value: ", v)
panic("fail")
}
seen[v] = true
}
}
func main() {
runtime.GOMAXPROCS(2)
c1 := make(chan int)
c2 := make(chan int)
c3 := make(chan int)
c4 := make(chan int)
cmux := make(chan int)
go sender(*iterations, c1, c2, c3, c4)
go mux(cmux, c1)
go mux(cmux, c2)
go mux(cmux, c3)
go mux(cmux, c4)
// We keep the recver because it might catch more bugs in the future.
// However, the result of the bug linked to at the top is that we'll
// end up panicing with: "throw: bad g->status in ready".
recver(cmux)
print("PASS\n")
}
|
