[patch] Document fork() behaviour for the Linux native AIO io_context

[patch] Document fork() behaviour for the Linux native AIO io_context

[Jeff Moyer]

Hi,

It was noted on lkml that the fork behaviour is documented for the posix
AIO calls, but not for the Linux native calls.  Here is a patch which
adds a small blurb that folks will hopefully find useful.

Signed-off-by: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>

Upon fork, the child process does not inherit the io_context_t data structures
returned by io_setup, and thus cannot submit further asynchronous I/O or
reap event completions for said contexts.
diff --git a/man2/fork.2 b/man2/fork.2
index ce93b3e..fb9008e 100644
--- a/man2/fork.2
+++ b/man2/fork.2
@@ -83,7 +83,9 @@ The child does not inherit timers from its parent
 The child does not inherit outstanding asynchronous I/O operations
 from its parent
 .RB ( aio_read (3),
-.BR aio_write (3)).
+.BR aio_write (3)),
+nor does it inherit the asynchronous io_context returned by
+.BR io_setup (2).
 .PP
 The process attributes in the preceding list are all specified
 in POSIX.1-2001.
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Re: [patch] Document fork() behaviour for the Linux native AIO io_context

[Michael Kerrisk]

Hi Jeff,

On Wed, Apr 15, 2009 at 5:54 AM, Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> Hi,
>
> It was noted on lkml that the fork behaviour is documented for the posix
> AIO calls, but not for the Linux native calls.  Here is a patch which
> adds a small blurb that folks will hopefully find useful.
>
> Signed-off-by: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>
> Upon fork, the child process does not inherit the io_context_t data structures
> returned by io_setup, and thus cannot submit further asynchronous I/O or
> reap event completions for said contexts.

Thanks.  I tweaked that very slightly, and have applied for man-pages-3.22.

Cheers,

Michael

--- a/man2/fork.2
+++ b/man2/fork.2
@@ -83,7 +83,9 @@ The child does not inherit timers from its parent
 The child does not inherit outstanding asynchronous I/O operations
 from its parent
 .RB ( aio_read (3),
-.BR aio_write (3)).
+.BR aio_write (3)),
+nor does it inherit outstanding asynchronous I/O context from its parent
+.RB ( io_setup (2)).
 .PP
 The process attributes in the preceding list are all specified
 in POSIX.1-2001.



> diff --git a/man2/fork.2 b/man2/fork.2
> index ce93b3e..fb9008e 100644
> --- a/man2/fork.2
> +++ b/man2/fork.2
> @@ -83,7 +83,9 @@ The child does not inherit timers from its parent
>  The child does not inherit outstanding asynchronous I/O operations
>  from its parent
>  .RB ( aio_read (3),
> -.BR aio_write (3)).
> +.BR aio_write (3)),
> +nor does it inherit the asynchronous io_context returned by
> +.BR io_setup (2).
>  .PP
>  The process attributes in the preceding list are all specified
>  in POSIX.1-2001.
>



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
git://git.kernel.org/pub/scm/docs/man-pages/man-pages.git
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html
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Re: [patch] Document fork() behaviour for the Linux native AIO io_context

[Jeff Moyer]

Michael Kerrisk <mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> writes:

> Hi Jeff,
>
> On Wed, Apr 15, 2009 at 5:54 AM, Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>> Hi,
>>
>> It was noted on lkml that the fork behaviour is documented for the posix
>> AIO calls, but not for the Linux native calls.  Here is a patch which
>> adds a small blurb that folks will hopefully find useful.
>>
>> Signed-off-by: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>
>> Upon fork, the child process does not inherit the io_context_t data structures
>> returned by io_setup, and thus cannot submit further asynchronous I/O or
>> reap event completions for said contexts.
>
> Thanks.  I tweaked that very slightly, and have applied for man-pages-3.22.

Your tweak doesn't really make sense, and it isn't grammatically
correct.  How about:

nor does it inherit any asynchronous I/O contexts from its parent.

You can add in "see io_setup" if you like.

Thanks!
Jeff

> Cheers,
>
> Michael
>
> --- a/man2/fork.2
> +++ b/man2/fork.2
> @@ -83,7 +83,9 @@ The child does not inherit timers from its parent
>  The child does not inherit outstanding asynchronous I/O operations
>  from its parent
>  .RB ( aio_read (3),
> -.BR aio_write (3)).
> +.BR aio_write (3)),
> +nor does it inherit outstanding asynchronous I/O context from its parent
> +.RB ( io_setup (2)).
>  .PP
>  The process attributes in the preceding list are all specified
>  in POSIX.1-2001.
>
>
>
>> diff --git a/man2/fork.2 b/man2/fork.2
>> index ce93b3e..fb9008e 100644
>> --- a/man2/fork.2
>> +++ b/man2/fork.2
>> @@ -83,7 +83,9 @@ The child does not inherit timers from its parent
>>  The child does not inherit outstanding asynchronous I/O operations
>>  from its parent
>>  .RB ( aio_read (3),
>> -.BR aio_write (3)).
>> +.BR aio_write (3)),
>> +nor does it inherit the asynchronous io_context returned by
>> +.BR io_setup (2).
>>  .PP
>>  The process attributes in the preceding list are all specified
>>  in POSIX.1-2001.
>>
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Re: [patch] Document fork() behaviour for the Linux native AIO io_context

[Michael Kerrisk]

Hi Jeff,

On Tue, Apr 28, 2009 at 12:46 AM, Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
> Michael Kerrisk <mtk.manpages-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> writes:
>
>> Hi Jeff,
>>
>> On Wed, Apr 15, 2009 at 5:54 AM, Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> wrote:
>>> Hi,
>>>
>>> It was noted on lkml that the fork behaviour is documented for the posix
>>> AIO calls, but not for the Linux native calls.  Here is a patch which
>>> adds a small blurb that folks will hopefully find useful.
>>>
>>> Signed-off-by: Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
>>>
>>> Upon fork, the child process does not inherit the io_context_t data structures
>>> returned by io_setup, and thus cannot submit further asynchronous I/O or
>>> reap event completions for said contexts.
>>
>> Thanks.  I tweaked that very slightly, and have applied for man-pages-3.22.
>
> Your tweak doesn't really make sense, and it isn't grammatically
> correct.  How about:
>
> nor does it inherit any asynchronous I/O contexts from its parent.
>
> You can add in "see io_setup" if you like.

Thanks for catching that.  I must have wrongly grabbed "outstanding"
from the previous phrase in the page.  I've made the change as below.

By the way, this raises a parallel question: what happens to
asynchronous I/O contexts on an execve(2)?

Cheers,

Michael

--- a/man2/fork.2
+++ b/man2/fork.2
@@ -83,7 +83,9 @@ The child does not inherit timers from its parent
 The child does not inherit outstanding asynchronous I/O operations
 from its parent
 .RB ( aio_read (3),
-.BR aio_write (3)).
+.BR aio_write (3)),
+nor does it inherit any asynchronous I/O contexts from its parent
+.RB ( see io_setup (2)).
 .PP
 The process attributes in the preceding list are all specified
 in POSIX.1-2001.
--
To unsubscribe from this list: send the line "unsubscribe linux-man" in
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