net: TCPConn.ReadFrom hangs when io.Reader is TCPConn or UnixConn, Linux kernel < 5.1 [1.21 backport]

[gopherbot]

@panjf2000 requested issue #63795 to be considered for backport to the next 1.21 minor release.

@sebastien-rosset Thanks for your efforts here.

Although this problem was caused by the CL in #59041, that issue focused on another problem originally, therefore I asked to open a new issue for this problem solely, for tracking purposes.

@gopherbot please consider this for backport to go1.21, it's a regression.

[gopherbot]

Change https://go.dev/cl/538117 mentions this issue: [release-branch.go1.21] internal/poll: add SPLICE_F_NONBLOCK flag for splice to avoid inconsistency with O_NONBLOCK

[cherrymui]

waiting for #63795 to be fixed.

[sebastien-rosset]

I see the fix has been committed to master: https://go-review.googlesource.com/c/go/+/536015, presumably it needs to be back-ported to 1.21.x and 1.22.x.

[cherrymui]

@sebastien-rosset Go 1.22 is not released yet, so there is no backport to Go 1.22.x. #63795 is still open, and it is not really clear if there is anything more needed to be done. We will take another look next week if things are clear by then. Thanks.

[sebastien-rosset]

Thanks. How about back porting to 1.21?

[cherrymui]

Backporting to 1.21 is this issue. We are waiting for #63795 to be closed.

[rabadin]

@cherrymui Looks like #63795 is fixed now... will the backport to 1.21 (https://go-review.googlesource.com/c/go/+/538117) be included in the upcoming 1.21.* release?

[bcmills]

@rabadin, I would expect that it will not be, since the backport change is not yet merged. Probably the next 1.21.* point release after this one.

[cherrymui]

Thanks for the update.

[rabadin]

Thanks the the heads up @bcmills.