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Date: Wed, 12 Jun 2024 10:10:21 -0700
From: Joe Damato <jdamato@...tly.com>
To: Rich Felker <dalias@...c.org>
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH] sys/epoll.h: add epoll ioctls

On Mon, Jun 10, 2024 at 10:15:25AM -0700, Joe Damato wrote:
> On Mon, Jun 10, 2024 at 12:05:52PM -0400, Rich Felker wrote:
> > On Sun, Jun 02, 2024 at 04:05:25PM -0700, Joe Damato wrote:
> > > On Wed, May 29, 2024 at 08:11:13AM -0700, Joe Damato wrote:
> > > > On Wed, May 29, 2024 at 09:17:07AM -0400, Rich Felker wrote:
> > > > > On Wed, May 29, 2024 at 06:49:59AM +0000, Joe Damato wrote:
> > > > > > add two ioctls to get and set struct epoll_params to allow users to
> > > > > > control epoll based busy polling of network sockets.
> > > > > > 
> > > > > > added to uapi in commit 18e2bf0edf4dd88d9656ec92395aa47392e85b61 (Linux
> > > > > > kernel 6.9 and newer).
> > > > > > ---
> > > > > >  include/sys/epoll.h | 12 ++++++++++++
> > > > > >  1 file changed, 12 insertions(+)
> > > > > > 
> > > > > > diff --git a/include/sys/epoll.h b/include/sys/epoll.h
> > > > > > index ac81a841..5f975c4a 100644
> > > > > > --- a/include/sys/epoll.h
> > > > > > +++ b/include/sys/epoll.h
> > > > > > @@ -7,6 +7,7 @@ extern "C" {
> > > > > >  
> > > > > >  #include <stdint.h>
> > > > > >  #include <sys/types.h>
> > > > > > +#include <sys/ioctl.h>
> > > > > >  #include <fcntl.h>
> > > > > >  
> > > > > >  #define __NEED_sigset_t
> > > > > > @@ -54,6 +55,17 @@ __attribute__ ((__packed__))
> > > > > >  #endif
> > > > > >  ;
> > > > > >  
> > > > > > +struct epoll_params {
> > > > > > +	uint32_t busy_poll_usecs;
> > > > > > +	uint16_t busy_poll_budget;
> > > > > > +	uint8_t prefer_busy_poll;
> > > > > > +
> > > > > > +	uint8_t __pad;
> > > > > > +};
> > > > > > +
> > > > > > +#define EPOLL_IOC_TYPE 0x8A
> > > > > > +#define EPIOCSPARAMS _IOW(EPOLL_IOC_TYPE, 0x01, struct epoll_params)
> > > > > > +#define EPIOCGPARAMS _IOR(EPOLL_IOC_TYPE, 0x02, struct epoll_params)
> > > > > >  
> > > > > >  int epoll_create(int);
> > > > > >  int epoll_create1(int);
> > > > > > -- 
> > > > > > 2.34.1
> > > > > 
> > > > > This is probably okay, but we should at least ask if sys/ioctl.h is
> > > > > going to be a namespace mess. Is the intent to bring all of it in, or
> > > > > just to get the EPIOC* macros which depend on _IOW and _IOR?
> > > > 
> > > > Yes, sys/ioctl.h is pulled in for the _IOW and _IOR macros.
> > > > Similar to, for example, sys/mtio.h in musl, which also pulls in
> > > > sys/ioctl.h.
> > > > 
> > > > > On glibc, does it pull in sys/ioctl.h?
> > > > 
> > > > Yes, the code I've submit for glibc does pull in sys/ioctl.h.
> > > > 
> > > > That code has been approved by a glibc committer, but not yet merged
> > > > to the tree (I assume that will happen in a few days):
> > > > 
> > > > https://sourceware.org/pipermail/libc-alpha/2024-May/157166.html
> > > 
> > > Just wanted to follow up on the above.
> > > 
> > > Were you expecting me to make any changes or did you want to wait
> > > until libc takes the code before accepting it?
> > > 
> > > FWIW:
> > > 
> > > uclibc has taken the patch here: 
> > >   https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/commit/?id=8bb33a2e1f2baec2078581d77e181f1ead5f51aa
> > > 
> > > And musl has similar code in include/sys/mount.h:
> > >   https://git.musl-libc.org/cgit/musl/tree/include/sys/mount.h#n8
> > 
> > I think it's okay as-is if this is what everyone else is doing too.
> > This is not a standard header so there aren't strong constraints on
> > what it can do; I just didn't want to be gratuitously more
> > namespace-invasive than on other systems with the same header.
> 
> OK, sure that makes sense.
> 
> BTW, since my email glibc has merged this:
> https://sourceware.org/git/?p=glibc.git;a=commit;h=92c270d32caf3f8d5a02b8e46c7ec5d9d0315158
> 
> Let me know if you'd like me to do anything else to help get this
> merged to musl.

Apologies on bumping the thread again, just wanted to also mention
the man-pages project has also taken the new man page documenting
the interface for glibc:

https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/commit/?h=ioctl&id=e450bcf6e35a5c227c5e80cdb4e44bb89516a5ee

Is there an equivalent documentation I should submit a similar
change to that is musl specific? If so, please let me know and I'd
be happy to do so.

Thanks,
Joe

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