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Date: Wed, 29 May 2024 08:11:10 -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 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

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