Re: [PATCH v2 08/35] entry: handle lazy rescheduling at user-exit

Peter Zijlstra
2024-05-28T16:12:39Z

On Mon, May 27, 2024 at 05:34:54PM -0700, Ankur Arora wrote:
> The scheduling policy for TIF_NEED_RESCHED_LAZY is to allow the
> running task to voluntarily schedule out, running it to completion.
>
> For archs with GENERIC_ENTRY, do this by adding a check in
> exit_to_user_mode_loop().
>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andy Lutomirski <luto@kernel.org>
> Originally-by: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> ---
> include/linux/entry-common.h | 2 +-
> kernel/entry/common.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/entry-common.h b/include/linux/entry-common.h
> index b0fb775a600d..f5bb19369973 100644
> --- a/include/linux/entry-common.h
> +++ b/include/linux/entry-common.h
> @@ -65,7 +65,7 @@
> #define EXIT_TO_USER_MODE_WORK \
> (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_UPROBE | \
> _TIF_NEED_RESCHED | _TIF_PATCH_PENDING | _TIF_NOTIFY_SIGNAL | \
> - ARCH_EXIT_TO_USER_MODE_WORK)
> + _TIF_NEED_RESCHED_LAZY | ARCH_EXIT_TO_USER_MODE_WORK)

Should we be wanting both TIF_NEED_RESCHED flags side-by-side?