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

go version go1.9.1 linux/arm64

Does this issue reproduce with the latest release?

Yes (reproduced on current tip).

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

GOARCH="arm64"
GOBIN=""
GOEXE=""
GOHOSTARCH="arm64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/tklauser/gopath"
GORACE=""
GOROOT="/home/tklauser/go"
GOTOOLDIR="/home/tklauser/go/pkg/tool/linux_arm64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build256498452=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"

What did you do?

Consider the following program which uses syscall.Select to unconditionally sleep for 2 milliseconds:

package main

import (
        "fmt"
        "syscall"
        "time"
)

func main() {
        t := syscall.Timeval{0 /*sec*/, 2000 /*usec*/}

        start := time.Now()
        _, err := syscall.Select(0, nil, nil, nil, &t)
        end := time.Now()

        if err == nil {
                fmt.Printf("select returned after %v\n", end.Sub(start))
        }
}

What did you expect to see?

I'd expect the program to print something similar to select returned after 2.0535ms (the exact number may obviously vary, but should be around 2ms). Running the program e.g. on linux/amd64 indeed produces the expected output.

What did you see instead?

Running the above program on linux/arm64 produces the output select returned after 249.68µs, i.e. the expired timeout is much less than 2ms.

The cause for this is that syscall.Select uses the SYS_PSELECT6 on linux/arm64 (and linux/mips64 for that matter, but I didn't check there). pselect6 expects the timeout argument of type struct timespec with nanosecond precision, while the classic select syscall expects a struct timeval with microsecond precision (see http://man7.org/linux/man-pages/man2/select.2.html, section "The timeout" for details).

Indeed, changing t := syscall.Timeval{0 /*sec*/, 2000 /*usec*/} to t := syscall.Timeval{0 /*sec*/, 2000 * 1000 /*usec*/} in the program above produces the expected output.

SYS_SELECT or SYS__NEWSELECT don't exist on linux/arm64, so the easiest solution is probably to add syscall.pselect and make syscall.Select a wrapper around it, converting the timeout argument. FWIW this is what glibc also does if neither __NR_select nor __NR__newselect is defined for a particular architecture.

Note that the same problem also exists in golang.org/x/sys/unix