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lib/osutil: Check PGID before trying to set it (fixes #4679) 

Fixes "permission denied" return when are already process group /
session leader.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4678
This commit is contained in:
Jakob Borg 2018-01-17 12:32:11 +00:00
parent 582539a1e6
commit e147db5233
1 changed files with 10 additions and 2 deletions
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12
lib/osutil/lowprio_linux.go
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@ -7,6 +7,7 @@
package osutil
import (
"os"
"syscall"
"github.com/pkg/errors"
@ -44,8 +45,15 @@ func SetLowPriority() error {
// Move ourselves to a new process group so that we can use the process
// group variants of Setpriority etc to affect all of our threads in one
// go. If this fails, bail, so that we don't affect things we shouldn't.
if err := syscall.Setpgid(0, 0); err != nil {
return errors.Wrap(err, "set process group")
// If we are already the leader of our own process group, do nothing.
if pgid, err := syscall.Getpgid(0); err != nil {
// This error really shouldn't happen
return errors.Wrap(err, "get process group")
} else if pgid != os.Getpid() {
// We are not process group leader. Elevate!
if err := syscall.Setpgid(0, 0); err != nil {
return errors.Wrap(err, "set process group")
}
}
// Process zero is "self", niceness value 9 is something between 0