runtime: selectgo need not lock all the channels involved in the select

[dreamerjackson]

i read the select function:

func selectgo(cas0 *scase, order0 *uint16, ncases int) (int, bool) {
   ...
	// lock all the channels involved in the select
	sellock(scases, lockorder)

}

why we should lock all the channels?
i think lock one by one when loop may be better , because it will quickly

[randall77]

Dmitry tried this a while ago: https://go-review.googlesource.com/c/go/+/7570
TL; DR it is tricky to get right. We never convinced ourselves it was correct.

[dreamerjackson]

Dmitry tried this a while ago: https://go-review.googlesource.com/c/go/+/7570
TL; DR it is tricky to get right. We never convinced ourselves it was correct.

most case it may will work ok,but select is one of the most important role in go, when channel in select increase and Concurrent oparate the channels, the performance will down.

[navytux]

See also: #8896