So the Go 1 memory model really make no guarantees that the following
program will print 1?
package main
import "fmt"
import "sync/atomic"
import "runtime"
func main() {
runtime.GOMAXPROCS(1)
var a, b int32 = 0, 0
go func() {
a = 1
atomic.AddInt32(&b, 1)
}()
for {
if n := atomic.LoadInt32(&b); n == 1 {
fmt.Println(a) // always print 1?
break
}
runtime.Gosched()
}
On Sunday, October 22, 2017 at 6:33:42 AM UTC-4, T L wrote:
>
>
>
> On Sunday, October 22, 2017 at 5:55:54 AM UTC-4, Jan Mercl wrote:
>>
>> On Sun, Oct 22, 2017 at 9:19 AM T L <tapi...@gmail.com> wrote:
>>
>> > why?
>>
>> The OP code with line numbes: https://play.golang.org/p/4fmiWqDDc1
>>
>> The main goroutine busy loops at lines 15-20. Because of that the
>> goroutine at line 10 may never run and thus line 17 may never get executed.
>> If so, line 18 and thus also lines 27 and above may also never get executed.
>>
>> --
>>
>> -j
>>
>
> Aha, yes, if GOMAXPROCS is 1, then the main goroutine will become greedy.
>
>
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