[release-branch.go1.4] undo CL 131750044 / 2d6d44ceb80e

««« CL 174450043 / 699cc091a16d
undo CL 131750044 / 2d6d44ceb80e

Breaks reading from stdin in parent after exec with SysProcAttr{Setpgid: true}.

package main

import (
        "fmt"
        "os"
        "os/exec"
        "syscall"
)

func main() {
        cmd := exec.Command("true")
        cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
        cmd.Run()

        fmt.Printf("Hit enter:")
        os.Stdin.Read(make([]byte, 100))
        fmt.Printf("Bye\n")
}

In go1.3, I type enter at the prompt and the program exits.
With the CL being rolled back, the program wedges at the
prompt.

««« original CL description
syscall: SysProcAttr job control changes

Making the child's process group the foreground process group and
placing the child in a specific process group involves co-ordination
between the parent and child that must be done post-fork but pre-exec.

LGTM=iant
R=golang-codereviews, gobot, iant, mikioh.mikioh
CC=golang-codereviews
https://golang.org/cl/131750044

»»»

LGTM=minux, dneil
R=dneil, minux
CC=golang-codereviews, iant, michael.p.macinnis
https://golang.org/cl/174450043
»»»

LGTM=minux
R=dneil, minux
CC=golang-codereviews
https://golang.org/cl/179970043

diff --git a/src/syscall/exec_bsd.go b/src/syscall/exec_bsd.go
index 7c2c1f7071a8094a43ff89ccb73a42ea103849ef..ff78f197f1fb30af337e1618264f56aa701a1302 100644 (file)
--- a/src/syscall/exec_bsd.go
+++ b/src/syscall/exec_bsd.go
@@ -19,8 +19,6 @@ type SysProcAttr struct {
        Setpgid    bool        // Set process group ID to new pid (SYSV setpgrp)
        Setctty    bool        // Set controlling terminal to fd 0
        Noctty     bool        // Detach fd 0 from controlling terminal
-       Foreground bool        // Set foreground process group to child's pid. (Implies Setpgid. Stdin should be a TTY)
-       Joinpgrp   int         // If != 0, child's process group ID. (Setpgid must not be set)
 }
 
 // Implemented in runtime package.
@@ -81,22 +79,7 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
        if r1 != 0 {
                // parent; return PID
                runtime_AfterFork()
-               pid = int(r1)
-
-               if sys.Joinpgrp != 0 {
-                       // Place the child in the specified process group.
-                       RawSyscall(SYS_SETPGID, r1, uintptr(sys.Joinpgrp), 0)
-               } else if sys.Foreground || sys.Setpgid {
-                       // Place the child in a new process group.
-                       RawSyscall(SYS_SETPGID, 0, 0, 0)
-
-                       if sys.Foreground {
-                               // Set new foreground process group.
-                               RawSyscall(SYS_IOCTL, uintptr(Stdin), TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
-                       }
-               }
-
-               return pid, 0
+               return int(r1), 0
        }
 
        // Fork succeeded, now in child.
@@ -118,30 +101,11 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
        }
 
        // Set process group
-       if sys.Joinpgrp != 0 {
-               // Place the child in the specified process group.
-               _, _, err1 = RawSyscall(SYS_SETPGID, r1, uintptr(sys.Joinpgrp), 0)
-               if err1 != 0 {
-                       goto childerror
-               }
-       } else if sys.Foreground || sys.Setpgid {
-               // Place the child in a new process group.
+       if sys.Setpgid {
                _, _, err1 = RawSyscall(SYS_SETPGID, 0, 0, 0)
                if err1 != 0 {
                        goto childerror
                }
-
-               if sys.Foreground {
-                       r1, _, _ = RawSyscall(SYS_GETPID, 0, 0, 0)
-
-                       pid := int(r1)
-
-                       // Set new foreground process group.
-                       _, _, err1 = RawSyscall(SYS_IOCTL, uintptr(Stdin), TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
-                       if err1 != 0 {
-                               goto childerror
-                       }
-               }
        }
 
        // Chroot

diff --git a/src/syscall/exec_linux.go b/src/syscall/exec_linux.go
index 72e2f0b69c82f64bf191515d6af4d5bc9d8949b6..042c20a46812feb1d88e0f928e7e61382480e64a 100644 (file)
--- a/src/syscall/exec_linux.go
+++ b/src/syscall/exec_linux.go
@@ -29,8 +29,6 @@ type SysProcAttr struct {
        Ctty        int            // Controlling TTY fd (Linux only)
        Pdeathsig   Signal         // Signal that the process will get when its parent dies (Linux only)
        Cloneflags  uintptr        // Flags for clone calls (Linux only)
-       Foreground  bool           // Set foreground process group to child's pid. (Implies Setpgid. Stdin should be a TTY)
-       Joinpgrp    int            // If != 0, child's process group ID. (Setpgid must not be set)
        UidMappings []SysProcIDMap // User ID mappings for user namespaces.
        GidMappings []SysProcIDMap // Group ID mappings for user namespaces.
 }
@@ -105,19 +103,6 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
                        Close(p[1])
                }
 
-               if sys.Joinpgrp != 0 {
-                       // Place the child in the specified process group.
-                       RawSyscall(SYS_SETPGID, r1, uintptr(sys.Joinpgrp), 0)
-               } else if sys.Foreground || sys.Setpgid {
-                       // Place the child in a new process group.
-                       RawSyscall(SYS_SETPGID, 0, 0, 0)
-
-                       if sys.Foreground {
-                               // Set new foreground process group.
-                               RawSyscall(SYS_IOCTL, uintptr(Stdin), TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
-                       }
-               }
-
                return pid, 0
        }
 
@@ -179,30 +164,11 @@ func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr
        }
 
        // Set process group
-       if sys.Joinpgrp != 0 {
-               // Place the child in the specified process group.
-               _, _, err1 = RawSyscall(SYS_SETPGID, r1, uintptr(sys.Joinpgrp), 0)
-               if err1 != 0 {
-                       goto childerror
-               }
-       } else if sys.Foreground || sys.Setpgid {
-               // Place the child in a new process group.
+       if sys.Setpgid {
                _, _, err1 = RawSyscall(SYS_SETPGID, 0, 0, 0)
                if err1 != 0 {
                        goto childerror
                }
-
-               if sys.Foreground {
-                       r1, _, _ = RawSyscall(SYS_GETPID, 0, 0, 0)
-
-                       pid := int(r1)
-
-                       // Set new foreground process group.
-                       _, _, err1 = RawSyscall(SYS_IOCTL, uintptr(Stdin), TIOCSPGRP, uintptr(unsafe.Pointer(&pid)))
-                       if err1 != 0 {
-                               goto childerror
-                       }
-               }
        }
 
        // Chroot