[PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[Josh Triplett]

Normally, system calls return EINVAL for flags they don't support.
Explicitly document that clone does *not* produce an error for these two
obsolete flags.

Signed-off-by: Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>
---
 man2/clone.2 | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/man2/clone.2 b/man2/clone.2
index 91c3684..10cef7d 100644
--- a/man2/clone.2
+++ b/man2/clone.2
@@ -534,7 +534,8 @@ This is good for hacking the system, but otherwise
 of not much use.
 Since 2.3.21 this flag can be
 specified only by the system boot process (PID 0).
-It disappeared in Linux 2.5.16.
+It disappeared in Linux 2.5.16.  Since then, the kernel silently ignores it
+without error.
 .TP
 .BR CLONE_PTRACE " (since Linux 2.2)"
 If
@@ -599,7 +600,8 @@ This flag was
 from Linux 2.6.25 onward,
 and was
 .I removed
-altogether in Linux 2.6.38.
+altogether in Linux 2.6.38.  Since then, the kernel silently ignores it without
+error.
 .\" glibc 2.8 removed this defn from bits/sched.h
 .TP
 .BR CLONE_SYSVSEM " (since Linux 2.5.10)"
-- 
2.1.4

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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[Michael Kerrisk (man-pages)]

On 02/27/2015 01:41 AM, Josh Triplett wrote:
> Normally, system calls return EINVAL for flags they don't support.
> Explicitly document that clone does *not* produce an error for these two
> obsolete flags.

Thanks, Josh! Applied.

Cheers,

Michael



> Signed-off-by: Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>
> ---
>  man2/clone.2 | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/clone.2 b/man2/clone.2
> index 91c3684..10cef7d 100644
> --- a/man2/clone.2
> +++ b/man2/clone.2
> @@ -534,7 +534,8 @@ This is good for hacking the system, but otherwise
>  of not much use.
>  Since 2.3.21 this flag can be
>  specified only by the system boot process (PID 0).
> -It disappeared in Linux 2.5.16.
> +It disappeared in Linux 2.5.16.  Since then, the kernel silently ignores it
> +without error.
>  .TP
>  .BR CLONE_PTRACE " (since Linux 2.2)"
>  If
> @@ -599,7 +600,8 @@ This flag was
>  from Linux 2.6.25 onward,
>  and was
>  .I removed
> -altogether in Linux 2.6.38.
> +altogether in Linux 2.6.38.  Since then, the kernel silently ignores it without
> +error.
>  .\" glibc 2.8 removed this defn from bits/sched.h
>  .TP
>  .BR CLONE_SYSVSEM " (since Linux 2.5.10)"
> 


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[josh-iaAMLnmF4UmaiuxdJuQwMA]

On Fri, Feb 27, 2015 at 07:42:44AM +0100, Michael Kerrisk (man-pages) wrote:
> On 02/27/2015 01:41 AM, Josh Triplett wrote:
> > Normally, system calls return EINVAL for flags they don't support.
> > Explicitly document that clone does *not* produce an error for these two
> > obsolete flags.
> 
> Thanks, Josh! Applied.

Doesn't appear to be in the current git repository.

- Josh Triplett
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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[Michael Kerrisk (man-pages)]

On 27 February 2015 at 17:31,  <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org> wrote:
> On Fri, Feb 27, 2015 at 07:42:44AM +0100, Michael Kerrisk (man-pages) wrote:
>> On 02/27/2015 01:41 AM, Josh Triplett wrote:
>> > Normally, system calls return EINVAL for flags they don't support.
>> > Explicitly document that clone does *not* produce an error for these two
>> > obsolete flags.
>>
>> Thanks, Josh! Applied.
>
> Doesn't appear to be in the current git repository.

Pushed now, Josh. (I needed to get another release out of the way first.)

Cheers,

Michael

-- 
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Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[josh-iaAMLnmF4UmaiuxdJuQwMA]

On Mon, Mar 02, 2015 at 05:27:38PM +0100, Michael Kerrisk (man-pages) wrote:
> On 27 February 2015 at 17:31,  <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org> wrote:
> > On Fri, Feb 27, 2015 at 07:42:44AM +0100, Michael Kerrisk (man-pages) wrote:
> >> On 02/27/2015 01:41 AM, Josh Triplett wrote:
> >> > Normally, system calls return EINVAL for flags they don't support.
> >> > Explicitly document that clone does *not* produce an error for these two
> >> > obsolete flags.
> >>
> >> Thanks, Josh! Applied.
> >
> > Doesn't appear to be in the current git repository.
> 
> Pushed now, Josh. (I needed to get another release out of the way first.)

No problem; thanks for the update.

Related issue: the errors section of clone.2 claims it'll return EPERM
for CLONE_PID by something other than PID 0 (meaning, outside the
kernel), but that doesn't actually happen.  Should that be dropped?  (I
can send a patch if so.)

- Josh Triplett
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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[Michael Kerrisk (man-pages)]

Hi Josh,

On 03/02/2015 05:40 PM, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org wrote:
> On Mon, Mar 02, 2015 at 05:27:38PM +0100, Michael Kerrisk (man-pages) wrote:
>> On 27 February 2015 at 17:31,  <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org> wrote:
>>> On Fri, Feb 27, 2015 at 07:42:44AM +0100, Michael Kerrisk (man-pages) wrote:
>>>> On 02/27/2015 01:41 AM, Josh Triplett wrote:
>>>>> Normally, system calls return EINVAL for flags they don't support.
>>>>> Explicitly document that clone does *not* produce an error for these two
>>>>> obsolete flags.
>>>>
>>>> Thanks, Josh! Applied.
>>>
>>> Doesn't appear to be in the current git repository.
>>
>> Pushed now, Josh. (I needed to get another release out of the way first.)
> 
> No problem; thanks for the update.
> 
> Related issue: the errors section of clone.2 claims it'll return EPERM
> for CLONE_PID by something other than PID 0 (meaning, outside the
> kernel), but that doesn't actually happen.  Should that be dropped?  (I
> can send a patch if so.)

I'd take a patch to fix that. (But note, if this is kernel behavior
that has changed over time, it would be valuable to document when
the change occurred.)

Cheers,

Michael

-- 
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Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
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Re: [PATCH] clone.2: Document that clone silently ignores CLONE_PID and CLONE_STOPPED

[Josh Triplett]

On Tue, Mar 03, 2015 at 08:02:23AM +0100, Michael Kerrisk (man-pages) wrote:
> Hi Josh,
> 
> On 03/02/2015 05:40 PM, josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org wrote:
> > On Mon, Mar 02, 2015 at 05:27:38PM +0100, Michael Kerrisk (man-pages) wrote:
> >> On 27 February 2015 at 17:31,  <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org> wrote:
> >>> On Fri, Feb 27, 2015 at 07:42:44AM +0100, Michael Kerrisk (man-pages) wrote:
> >>>> On 02/27/2015 01:41 AM, Josh Triplett wrote:
> >>>>> Normally, system calls return EINVAL for flags they don't support.
> >>>>> Explicitly document that clone does *not* produce an error for these two
> >>>>> obsolete flags.
> >>>>
> >>>> Thanks, Josh! Applied.
> >>>
> >>> Doesn't appear to be in the current git repository.
> >>
> >> Pushed now, Josh. (I needed to get another release out of the way first.)
> > 
> > No problem; thanks for the update.
> > 
> > Related issue: the errors section of clone.2 claims it'll return EPERM
> > for CLONE_PID by something other than PID 0 (meaning, outside the
> > kernel), but that doesn't actually happen.  Should that be dropped?  (I
> > can send a patch if so.)
> 
> I'd take a patch to fix that. (But note, if this is kernel behavior
> that has changed over time, it would be valuable to document when
> the change occurred.)

The manpage already documents that earlier, when mentioning CLONE_PID:

       CLONE_PID (obsolete)
              If  CLONE_PID is set, the child process is created with the same
              process ID as the calling process.  This is good for hacking the
              system,  but  otherwise of not much use.  Since 2.3.21 this flag
              can be specified only by the system boot process  (PID  0).   It
              disappeared in Linux 2.5.16.

- Josh Triplett
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