From: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>,
akpm@linux-foundation.org, viro@zeniv.linux.org.uk,
torvalds@linux-foundation.org, drepper@gmail.com,
linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH] nextfd(2)
Date: Tue, 10 Apr 2012 20:09:56 -0400 [thread overview]
Message-ID: <CAHGf_=rsJ8o8Fnd2z5Z8jHGc=cz370ay0_t3bhkiYRCBh3puVw@mail.gmail.com> (raw)
In-Reply-To: <4F7F1864.8090606@zytor.com>
On Fri, Apr 6, 2012 at 12:23 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 04/06/2012 02:54 AM, Alexey Dobriyan wrote:
>>
>> Without proc knowledge about fdtable is gathered linearly and still unreliable.
>> With nextfd(2), even procful environments could lose several failure branches.
>> And they can keep old dumb fd++ or smart /proc/self/fd loops for a change.
>>
>
> Incidentally, if we were to create a system call for this -- which I so
> far see no reason for -- I would make it return a select-style bitmask
> of file descriptors in use, not a "next fd" which would require a system
> call per iteration.
I know the reason. fcntl(F_NEXT) is one of a proposal of next SUS enhancement.
http://austingroupbugs.net/view.php?id=149
nextfd() has a semantics of F_NEXT.
Next, why shoundn't we implement fcntl(F_NEXT) in our kernel? I think
we have two reason.
1) As linus pointed out, linux specific "flags" argument may be useful.
2) The name of F_NEXT is not fixed yet. another url of the austin says
it is FD_NEXT.
So, we can't choose right name yet. Moreover, A meanings of 3rd
argument of F_NEXT
haven't been fixed.
I dont think following #ifdef is insane. but glibc also can provide
correct F_NEXT when next SUS is published.
#ifdef FOO
#define NEXTFD(fd) nextfd(fd, flags)
#else
#define NEXTFD(fd) fcntl(fd, F_NEXT, O_FDWR)
#endif
In short, kernel developer don't care any standard at all. but
application programmer usually care it.
next prev parent reply other threads:[~2012-04-11 0:10 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-01 12:57 [PATCH] nextfd(2) Alexey Dobriyan
2012-04-01 13:58 ` Konstantin Khlebnikov
2012-04-01 21:30 ` Alexey Dobriyan
2012-04-02 0:09 ` Alan Cox
2012-04-02 8:38 ` Konstantin Khlebnikov
2012-04-02 9:26 ` Cyrill Gorcunov
2012-04-01 15:43 ` Eric Dumazet
2012-04-01 21:31 ` Alexey Dobriyan
2012-04-01 21:36 ` Alan Cox
2012-04-01 17:20 ` Linus Torvalds
2012-04-01 18:28 ` Valentin Nechayev
2012-04-01 21:33 ` Alexey Dobriyan
2012-04-01 19:21 ` Arnd Bergmann
2012-04-01 21:35 ` Alexey Dobriyan
2012-04-01 22:05 ` H. Peter Anvin
2012-04-04 12:13 ` Arnd Bergmann
2012-04-01 22:03 ` H. Peter Anvin
2012-04-01 22:13 ` H. Peter Anvin
2012-04-02 0:08 ` Alan Cox
2012-04-30 9:58 ` Valentin Nechayev
2012-04-02 1:19 ` Kyle Moffett
2012-04-02 1:37 ` H. Peter Anvin
2012-04-02 11:37 ` Ulrich Drepper
2012-04-06 9:54 ` Alexey Dobriyan
2012-04-06 15:27 ` Colin Walters
2012-04-06 16:14 ` H. Peter Anvin
2012-04-06 20:16 ` Alexey Dobriyan
2012-04-06 20:33 ` H. Peter Anvin
2012-04-06 21:02 ` H. Peter Anvin
2012-04-12 10:54 ` Alexey Dobriyan
2012-04-12 11:11 ` Alan Cox
2012-04-12 13:35 ` Alexey Dobriyan
2012-04-12 13:51 ` H. Peter Anvin
2012-04-12 19:21 ` Alexey Dobriyan
2012-04-12 14:09 ` Eric Dumazet
2012-04-06 16:23 ` H. Peter Anvin
2012-04-07 21:21 ` Ben Pfaff
2012-04-11 0:12 ` KOSAKI Motohiro
2012-04-11 0:09 ` KOSAKI Motohiro [this message]
2012-04-11 17:58 ` H. Peter Anvin
2012-04-11 18:04 ` Linus Torvalds
2012-04-11 18:11 ` H. Peter Anvin
2012-04-11 19:46 ` KOSAKI Motohiro
2012-04-11 19:49 ` H. Peter Anvin
2012-04-11 20:23 ` KOSAKI Motohiro
2012-04-11 20:32 ` H. Peter Anvin
2012-04-17 18:12 ` KOSAKI Motohiro
2012-04-11 18:00 ` H. Peter Anvin
2012-04-11 19:20 ` KOSAKI Motohiro
2012-04-11 19:22 ` H. Peter Anvin
2012-04-11 19:26 ` KOSAKI Motohiro
2012-04-11 19:28 ` H. Peter Anvin
2012-04-11 19:31 ` KOSAKI Motohiro
2012-04-11 19:32 ` H. Peter Anvin
2012-04-02 23:17 ` KOSAKI Motohiro
2012-04-02 23:56 ` H. Peter Anvin
2012-04-04 11:51 ` Ulrich Drepper
2012-04-04 16:38 ` KOSAKI Motohiro
2012-04-04 16:43 ` Ulrich Drepper
2012-04-04 17:07 ` KOSAKI Motohiro
2012-04-04 17:49 ` Ulrich Drepper
2012-04-04 18:08 ` KOSAKI Motohiro
2012-04-04 16:31 ` KOSAKI Motohiro
2012-04-04 17:10 ` Colin Walters
2012-04-04 17:25 ` Colin Walters
2012-04-04 23:35 ` KOSAKI Motohiro
2012-04-04 18:44 ` H. Peter Anvin
2012-04-03 19:21 ` Colin Walters
2012-04-04 3:01 ` Al Viro
2012-04-04 17:10 ` KOSAKI Motohiro
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