code review 7308102: runtime: fix running under nohup

runtime: fix running under nohup

There are two ways nohup(1) might be implemented:
it might mask away the signal, or it might set the handler
to SIG_IGN, both of which are inherited across fork+exec.
So two fixes:

* Make sure to preserve the inherited signal mask at
minit instead of clearing it.

* If the SIGHUP handler is SIG_IGN, leave it that way.

Fixes issue 4491.

[rsc, 2013-02-15 05:49:36]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go/

[mikio, 2013-02-15 09:04:57]

https://codereview.appspot.com/7308102/diff/4001/src/pkg/runtime/signal_freeb...
File src/pkg/runtime/signal_freebsd_amd64.c (right):

https://codereview.appspot.com/7308102/diff/4001/src/pkg/runtime/signal_freeb...
src/pkg/runtime/signal_freebsd_amd64.c:141: if(i == SIGHUP) {
perhaps you mean;
if(m != &runtime.m0 && i == SIGHUP) {

[mikio, 2013-02-15 09:10:33]

runtime+cgo test still fails on freebsd, hm.

[iant, 2013-02-15 15:56:09]

LGTM

[rsc, 2013-02-15 16:00:45]

FWIW I do expect this to break on some systems. That's what the dashboard is
for.

https://codereview.appspot.com/7308102/diff/4001/src/pkg/runtime/signal_freeb...
File src/pkg/runtime/signal_freebsd_amd64.c (right):

https://codereview.appspot.com/7308102/diff/4001/src/pkg/runtime/signal_freeb...
src/pkg/runtime/signal_freebsd_amd64.c:141: if(i == SIGHUP) {
On 2013/02/15 09:04:57, mikio wrote:
> perhaps you mean;
> if(m != &runtime.m0 && i == SIGHUP) {

I really do mean no matter what. Except for uses of os/signal, this only runs on
m0 anyway.

[rsc, 2013-02-15 16:19:05]

*** Submitted as https://code.google.com/p/go/source/detail?r=a61065d9bf0b ***

runtime: fix running under nohup

There are two ways nohup(1) might be implemented:
it might mask away the signal, or it might set the handler
to SIG_IGN, both of which are inherited across fork+exec.
So two fixes:

* Make sure to preserve the inherited signal mask at
minit instead of clearing it.

* If the SIGHUP handler is SIG_IGN, leave it that way.

Fixes issue 4491.

R=golang-dev, mikioh.mikioh, iant
CC=golang-dev
https://codereview.appspot.com/7308102