code review 6037048: runtime: use __tfork() syscall on openbsd

runtime: use __tfork() syscall on openbsd

Switch from using the rfork() syscall on OpenBSD, to the __tfork()
syscall.  The __tfork() syscall is the preferred way of creating
system threads and the rfork() syscall has recently been removed.

Note: this will break compatibility with OpenBSD releases prior to 5.1.

[jsing, 2012-04-23 16:41:24]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://go.googlecode.com/hg/

[jsing, 2012-04-23 17:22:07]

FTR OpenBSD 5.1 is the next stable release, which will be available from the 1st
of May 2012. If there is sufficient demand we can support both rfork() and
__tfork(), selecting the correct syscall based on the kernel version detected at
runtime.

However, since Go is not officially supported on OpenBSD (yet), I think that
breaking backwards compatibility is reasonable. If anything, I would suggest
targeting OpenBSD 5.2 (due for release 1st November 2012) since, at this stage,
rthreads will be enabled by default and we should be able to support/enable cgo.

[bradfitz, 2012-04-23 17:27:16]

Out of curiosity, do OpenBSD users tend to follow the latest releases
pretty closely?

On Mon, Apr 23, 2012 at 10:22 AM, <jsing@google.com> wrote:

> FTR OpenBSD 5.1 is the next stable release, which will be available from
> the 1st of May 2012. If there is sufficient demand we can support both
> rfork() and __tfork(), selecting the correct syscall based on the kernel
> version detected at runtime.
>
> However, since Go is not officially supported on OpenBSD (yet), I think
> that breaking backwards compatibility is reasonable. If anything, I
> would suggest targeting OpenBSD 5.2 (due for release 1st November 2012)
> since, at this stage, rthreads will be enabled by default and we should
> be able to support/enable cgo.
>
>
http://codereview.appspot.com/**6037048/<http://codereview.appspot.com/6037048/>
>

[dho, 2012-04-23 17:32:35]

Op 23 april 2012 13:27 heeft Brad Fitzpatrick <bradfitz@golang.org>
het volgende geschreven:
> Out of curiosity, do OpenBSD users tend to follow the latest releases pretty
> closely?

In my experience some do, some don't. Depends on the policy of where
ever they're running. Corporate tends to lag behind, people I know
tend to go so far as to run snapshot releases (but I know more OpenBSD
developers than vanilla users, so this might be skewed). I would say
that this really doesn't matter much until rthreads are enabled by
default as Go can't work effectively until then and it's hard to say
you support an OS if it's not working OOTB.

LGTM and /agree with targeting 5.2.

--dho

> On Mon, Apr 23, 2012 at 10:22 AM, <jsing@google.com> wrote:
>>
>> FTR OpenBSD 5.1 is the next stable release, which will be available from
>> the 1st of May 2012. If there is sufficient demand we can support both
>> rfork() and __tfork(), selecting the correct syscall based on the kernel
>> version detected at runtime.
>>
>> However, since Go is not officially supported on OpenBSD (yet), I think
>> that breaking backwards compatibility is reasonable. If anything, I
>> would suggest targeting OpenBSD 5.2 (due for release 1st November 2012)
>> since, at this stage, rthreads will be enabled by default and we should
>> be able to support/enable cgo.
>>
>> http://codereview.appspot.com/6037048/
>
>

[rsc, 2012-04-25 03:19:47]

LGTM

[jsing, 2012-04-25 13:50:38]

On 24 April 2012 03:27, Brad Fitzpatrick <bradfitz@golang.org> wrote:

> Out of curiosity, do OpenBSD users tend to follow the latest releases
> pretty closely?
>

Basically what Devon said :)

There are generally two groups of users - the first are
developers/enthusiasts who run -current and regularly update to current
snapshots, the second are industry/regular users who run stable releases.
Only the last two stable releases are officially supported by the OpenBSD
project, which means that regular users are expected to be running either
4.9 or 5.0 (or 5.0 and 5.1 as soon as 5.1 is released).

If someone wants to run Go on OpenBSD, upgrading to 5.1 is not that big of
a challenge and it means that we do not have to provide backwards
compatibility cruft (they would still need to enable rthreads manually).
However, since rthreads should be on by default in 5.2, we probably should
target 5.2 as a Go supported release.


> On Mon, Apr 23, 2012 at 10:22 AM, <jsing@google.com> wrote:
>
>> FTR OpenBSD 5.1 is the next stable release, which will be available from
>> the 1st of May 2012. If there is sufficient demand we can support both
>> rfork() and __tfork(), selecting the correct syscall based on the kernel
>> version detected at runtime.
>>
>> However, since Go is not officially supported on OpenBSD (yet), I think
>> that breaking backwards compatibility is reasonable. If anything, I
>> would suggest targeting OpenBSD 5.2 (due for release 1st November 2012)
>> since, at this stage, rthreads will be enabled by default and we should
>> be able to support/enable cgo.
>>
>>
http://codereview.appspot.com/**6037048/<http://codereview.appspot.com/6037048/>
>>
>
>

[jsing, 2012-04-25 14:08:15]

*** Submitted as http://code.google.com/p/go/source/detail?r=34a544cf1583 ***

runtime: use __tfork() syscall on openbsd

Switch from using the rfork() syscall on OpenBSD, to the __tfork()
syscall.  The __tfork() syscall is the preferred way of creating
system threads and the rfork() syscall has recently been removed.

Note: this will break compatibility with OpenBSD releases prior to 5.1.

R=golang-dev, bradfitz, devon.odell, rsc
CC=golang-dev
http://codereview.appspot.com/6037048