Potential unprotected critical zone?

[abbychau]

Wanna know if it is an unprotected critical zone between 121 and 122

go-ringbuf/mpmc/rb.go

Line 122 in 73252d2

if atomic.LoadUint64(&holder.readWrite) == 0 {

[hedzr]

the ever original idea is:

cas holder.readweite from 0 to 2 must not be failed, logically. so, line 122 would never get in control.
line 122-126 is just a defensive block. it could be remove safely.

if it really reached, the enqueue or dequeue would be failure.

[abbychau]

120-123 looks like a potential spinlock to me, but 122 looks like getting away from the spin. so i asked why 121 and 122 works like this.
Kind of unclear to me about the whole retry block ^^; Could you give a bit explanation?