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os: EINTR on Darwin when reading from os.Stdin #22838

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tibbes opened this issue Nov 21, 2017 · 4 comments
Closed

os: EINTR on Darwin when reading from os.Stdin #22838

tibbes opened this issue Nov 21, 2017 · 4 comments
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FrozenDueToAge NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
Milestone
Go1.10

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@tibbes
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tibbes commented Nov 21, 2017 •
edited

What did you do?

I built this program on a Mac, and also cross-compiled it using GOOS=linux, then ran it on both platforms to see what happened when I hit Ctrl-Z and resumed the program using fg 1.

package main

import (
        "bufio"
        "fmt"
        "os"
)

func main() {
        scanner := bufio.NewScanner(os.Stdin)
        for scanner.Scan() {
        }
        fmt.Println(scanner.Err())
}

What did you see on Linux?

$ ./tmp
^Z
[1]+  Stopped                 ./tmp
$ fg 1
./tmp

What did you see on Darwin (macOS)?

$ ./tmp
^Z
[1]+  Stopped                 ./tmp
$ fg 1
./tmp
read /dev/stdin: interrupted system call
$

What would you expect?

I would expect the behaviour to be the same on both platforms. A search of other issues indicated that the following may be relevant:

System details

go version go1.9.2 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/julian/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.9.2/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.9.2/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/x1/vfmlq7554nx8t6hzhl8804p40000gn/T/go-build975276148=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
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"
GOROOT/bin/go version: go version go1.9.2 darwin/amd64
GOROOT/bin/go tool compile -V: compile version go1.9.2
uname -v: Darwin Kernel Version 17.2.0: Fri Sep 29 18:27:05 PDT 2017; root:xnu-4570.20.62~3/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.13.1
BuildVersion:	17B48
lldb --version: lldb-900.0.57
  Swift-4.0
@bradfitz bradfitz changed the title EINTR on Darwin when reading from os.Stdin os: EINTR on Darwin when reading from os.Stdin Nov 21, 2017
@bradfitz bradfitz added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Nov 21, 2017
@bradfitz bradfitz added this to the Go1.10 milestone Nov 21, 2017
@bradfitz
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I can reproduce on Go tip (after Go 1.9) and on a macOS version one before yours:

brad5k:~ $ ./in 
^Z
[1]+  Stopped                 ./in
brad5k:~ $ fg
./in
read /dev/stdin: interrupted system call
brad5k:~ $ sw_vers 
ProductName:	Mac OS X
ProductVersion:	10.12.6
BuildVersion:	16G1036

@ianlancetaylor
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That is rather annoying. We don't install a SIGTSTP signal, nor should we. So we just take the default action. It looks like on GNU/Linux the default action is to not interrupt a read, but on MacOS it is.

@ianlancetaylor
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The fix took 10 seconds, the test case took five hours.

@gopherbot
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Change https://golang.org/cl/79215 mentions this issue: internal/poll: loop on EINTR in Read on Darwin

@golang golang locked and limited conversation to collaborators Nov 22, 2018
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@bradfitz @ianlancetaylor @tibbes @gopherbot