Ian, thank you very much for the suggestion to use atomics.
Unfortunately, for a standard SPSC ring buffer, I don't think it does the
trick.
I am attaching a simple ring buffer program at the end.
If you run 'go run -race main.go' on the example,
a race will occur.
The race that occurs is a write, then read to the
same element of a slice on two different goroutines.
Of course a race-detected is expected.
This can be fixed by mutexing Put() and Get(),
because through some magic, mutexs affect the tables/tags
the race detector maintains in order to catch races.
Using sync.atomic on the ring buffer indexes doesn't
affect the race-detector state for read and writes.
I spent more time investigating, it seems there are
two ways to make a traditional ring buffer compatible
with the race detector:
1. Use build tags to conditionally Lock/Unlock mutexes
where you would not actually need them, in order to reset
the race detector on the object crossing goroutines.
2. Use the pragma //go:linkname to get access to the 'runtime.race'
functions, in order to call Enable()/Disable/ReleaseMerge/Aquire
as sync.Pool does in order to make the race detector happy.
If there are other methods, please let me know!
Thanks for any feedback!
Cameron/Seattle
package main
import (
"sync/atomic"
"time"
)
type RB struct {
//mu sync.Mutex
buf []interface{}
start, end int64
}
const N = 10
func NewRB() *RB {
return &RB{buf: make([]interface{}, N)}
}
func (r *RB) Put(x interface{}) {
// mu.Lock()
// defer mu.Unlock()
r.buf[r.end] = x
atomic.AddInt64(&r.end,1)
//r.end++
r.end %= N
}
func (r *RB) Get() interface{} {
// mu.Lock()
// defer mu.Unlock()
v := r.buf[r.start]
atomic.AddInt64(&r.start,1)
//r.start++
r.start %= N
return v
}
func main() {
r := NewRB()
go func() {
r.Put(12345)
}()
time.Sleep(time.Millisecond)
a := r.Get().(int)
println(a)
}
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