Re: [PATCH v1 1/2] linux: Implement sched_yield in C

["H.J. Lu" <hjl.tools@gmail.com>]

On Wed, Jun 7, 2023 at 12:46 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
>
> This is in preperation for a minor optimization before expected
> context switches.
> ---
>  sysdeps/unix/sysv/linux/sched_yield.c | 27 +++++++++++++++++++++++++++
>  sysdeps/unix/sysv/linux/syscalls.list |  1 -
>  2 files changed, 27 insertions(+), 1 deletion(-)
>  create mode 100644 sysdeps/unix/sysv/linux/sched_yield.c
>
> diff --git a/sysdeps/unix/sysv/linux/sched_yield.c b/sysdeps/unix/sysv/linux/sched_yield.c
> new file mode 100644
> index 0000000000..154bf725b0
> --- /dev/null
> +++ b/sysdeps/unix/sysv/linux/sched_yield.c
> @@ -0,0 +1,27 @@
> +/* Yield current process.  Linux specific syscall.
> +   Copyright (C) 2023 Free Software Foundation, Inc.
> +   This file is part of the GNU C Library.
> +
> +   The GNU C Library is free software; you can redistribute it and/or
> +   modify it under the terms of the GNU Lesser General Public
> +   License as published by the Free Software Foundation; either
> +   version 2.1 of the License, or (at your option) any later version.
> +
> +   The GNU C Library is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> +   Lesser General Public License for more details.
> +
> +   You should have received a copy of the GNU Lesser General Public
> +   License along with the GNU C Library; if not, see
> +   <https://www.gnu.org/licenses/>.  */
> +
> +#include <sysdep.h>
> +
> +int
> +__sched_yield (void)
> +{
> +    return INLINE_SYSCALL_CALL (sched_yield);
> +}
> +libc_hidden_def (__sched_yield);
> +weak_alias (__sched_yield, sched_yield)
> diff --git a/sysdeps/unix/sysv/linux/syscalls.list b/sysdeps/unix/sysv/linux/syscalls.list
> index 73e941ef89..5f571df937 100644
> --- a/sysdeps/unix/sysv/linux/syscalls.list
> +++ b/sysdeps/unix/sysv/linux/syscalls.list
> @@ -59,7 +59,6 @@ sched_primax  -       sched_get_priority_max  i:i     __sched_get_priority_max        sched_get_pri
>  sched_primin   -       sched_get_priority_min  i:i     __sched_get_priority_min        sched_get_priority_min
>  sched_setp     -       sched_setparam  i:ip    __sched_setparam        sched_setparam
>  sched_sets     -       sched_setscheduler      i:iip   __sched_setscheduler    sched_setscheduler
> -sched_yield    -       sched_yield     i:      __sched_yield   sched_yield
>  setfsgid       EXTRA   setfsgid        i:i     setfsgid
>  setfsuid       EXTRA   setfsuid        i:i     setfsuid
>  setpgid                -       setpgid         i:ii    __setpgid       setpgid
> --
> 2.34.1


Is this really needed?   We can add x86-64 specific sched_yield.c.


-- 
H.J.