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net: ReadFromUDP falls into busy waiting on empty UDP packet #59704

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fumiama opened this issue Apr 19, 2023 · 1 comment
Closed

net: ReadFromUDP falls into busy waiting on empty UDP packet #59704

fumiama opened this issue Apr 19, 2023 · 1 comment

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@fumiama
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fumiama commented Apr 19, 2023

What version of Go are you using (go version)?

$ go version
go version go1.20.3 darwin/amd64

Does this issue reproduce with the latest release?

Yes, this is the latest version.

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE="auto"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/rumia/Library/Caches/go-build"
GOENV="/Users/rumia/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/rumia/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/rumia/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.20.3"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/rumia/Documents/src/alpacapi/go.mod"
GOWORK=""
CGO_CFLAGS="-O2 -g"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-O2 -g"
CGO_FFLAGS="-O2 -g"
CGO_LDFLAGS="-O2 -g"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/45/fs2wrr5548dbhlwc0j99_js40000gp/T/go-build815319731=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Here is a small test.

package main

import (
	"net"
	"net/netip"
	"testing"
)

func TestOnEmptyUDP(t *testing.T) {
	listener, err := net.ListenUDP("udp", net.UDPAddrFromAddrPort(netip.MustParseAddrPort("127.0.0.1:8888")))
	if err != nil {
		t.Fatal(err)
	}
	t.Log("listening on", listener.LocalAddr())
	buf := make([]byte, 4096)
	nzerocnt := 0
	go func() {
		conn, err := net.DialUDP("udp", nil, net.UDPAddrFromAddrPort(netip.MustParseAddrPort("127.0.0.1:8888")))
		if err != nil {
			panic(err)
		}
		_, _ = conn.Write(nil)
		_ = conn.Close()
	}()
	for n, remo, err := listener.ReadFromUDP(buf); err == nil; t.Log("recv from", remo) {
		if n == 0 {
			nzerocnt++
			if nzerocnt >= 4096 {
				t.Fatal("unexpected zero-loop")
			}
		}
	}
}

What did you expect to see?

The test will reach a timeout after 30s.

What did you see instead?

unexpected zero-loop triggered.

2CA8C6160F87B321A9BD489362031A32

8A4FC8D40991F39F54DD717D63732B8E

D2C6284B4782CF7FF1F4A096DCE000E9

B8AC2FA74D32B5E5C4A4120C8B77AFD8
@fumiama
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fumiama commented Apr 19, 2023

i got a mistake. sorry.

@fumiama fumiama closed this as completed Apr 19, 2023
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@fumiama