runtime: tight loop hangs process completely after some time #15442
Description
Please answer these questions before submitting your issue. Thanks!
- What version of Go are you using (
go version)?
go version go1.6.2 windows/amd64 - What operating system and processor architecture are you using (
go env)?
Windows 10.0.10586 am64 - What did you do?
Ran this code
package main
import (
"log"
"runtime"
)
func main() {
runtime.GOMAXPROCS(2)
ch := make(chan bool)
go func() {
for {
ch <- true
log.Println("sent")
}
}()
go func() {
for {
<-ch
log.Println("received")
}
}()
for {
}
}
- What did you expect to see?
Process printing "sent" and "received" until terminated - What did you see instead?
Process runs and prints as expected for about 2 seconds and then hangs. Nothing is printed after that, process just eats up CPU. No panics or anything.
I put runtime.GOMAXPROCS(2) to make sure that there're multiple threads that goroutines can ran on. Obviously with runtime.GOMAXPROCS(1) process would hang immediately as expected - for loop will not yield execution.
I tried to replace the for loop with this so that main goroutine can yield execution:
go func() {
for {
}
}()
select {}
But exactly the same thing happens. Now, if I put time.Sleep(10 * time.Millisecond) or longer after log.Println("sent") then process no longer hangs. I ran it for a minute and it's just kept going. Don't know, maybe it will still hang much later. If I change it to 2 ms then it hangs after 30 seconds. I tried to collect trace data but it looks like it gets corrupted because trace doesn't finish. When I try to view the trace it says "failed to parse trace: no EvFrequency event".
Everything behaves exactly the same on Mac OSX El capitan 10.11.4 (15E65) Go 1.6.2
I read the #10958 but here the weird thing is that it actually runs for awhile completely fine and only after that it hangs.