Re: [PATCH v2 0/6] sched: dynamic: Simplify PREEMPT_DYNAMIC

[Jinjie Ruan]

在 2026/8/4 3:17, Mark Rutland 写道:
> All architectures which currently suppoort PREEMPT_DYNAMIC select
> ARCH_HAS_PREEMPT_LAZY.  On architectures which select
> ARCH_HAS_PREEMPT_LAZY, it has not been possible to select the NONE and
> VOLUNTARY preemption models since v7.0 due to commit:
> 
>   7dadeaa6e851 ("sched: Further restrict the preemption modes")
> 
> Hence in practice PREEMPT_DYNAMIC no longer supports the NONE or
> VOLUNTARY preemption models.
> 
> This series makes the de-facto situation official by making
> PREEMPT_DYNAMIC depend on ARCH_HAS_PREEMPT_LAZY, and removing redundant
> code.
> 
> Since v1, I've had to rebase atop v7.2-rc4 to avoid a conflict with
> commit:
> 
>   a2c02aa0c6ca ("powerpc: Remove dead non-preemption code")
> 
> Given this is now late in the cycle, and given the tip:sched/core branch
> is based on v7.2-rc1, I suspect tip folk might not want to queue this
> now. Please let me know what you'd prefer; I'm happy to rebase and
> resend after v7.3-rc1.
> 
> Since v1:
> * Rebase to v7.2-rc4
> * Apply Revied-by tags.
> * Fix typos in commit messages.
> * Add patch to cleanup accessors (per Shrikanth's comment)
> 
> Mark.
> 
> Mark Rutland (6):
>   sched: dynamic: Make PREEMPT_DYNAMIC depend on ARCH_HAS_PREEMPT_LAZY
>   sched: dynamic: Simplify {cond,might}_resched()


Hi Mark,

We also need to update the Doc.

--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5410,8 +5410,6 @@ Kernel parameters

        preempt=        [KNL]
                        Select preemption mode if you have
CONFIG_PREEMPT_DYNAMIC
-                       none - Limited to cond_resched() calls
-                       voluntary - Limited to cond_resched() and
might_sleep() calls
                        full - Any section that isn't explicitly preempt
disabled
                               can be preempted anytime.  Tasks will
also yield
                               contended spinlocks (if the critical
section isn't

Best regards,
Jinjie

>   sched: dynamic: Simplify preempt_schedule{,_notrace}()
>   sched: dynamic: Simplify irqentry_exit_cond_resched()
>   sched: dynamic: Remove HAVE_PREEMPT_DYNAMIC_{CALL,KEY}
>   sched: dynamic: Simplify preempt model accessors
> 
>  arch/Kconfig                     |  38 -------
>  arch/arm64/Kconfig               |   1 -
>  arch/arm64/include/asm/preempt.h |  10 --
>  arch/loongarch/Kconfig           |   1 -
>  arch/powerpc/Kconfig             |   1 -
>  arch/riscv/Kconfig               |   1 -
>  arch/s390/Kconfig                |   1 -
>  arch/s390/include/asm/preempt.h  |  11 --
>  arch/x86/Kconfig                 |   1 -
>  arch/x86/include/asm/preempt.h   |  28 -----
>  include/asm-generic/preempt.h    |  10 --
>  include/linux/irq-entry-common.h |  17 +--
>  include/linux/kernel.h           |  20 ----
>  include/linux/preempt.h          |  20 ++--
>  include/linux/sched.h            |  31 +-----
>  kernel/Kconfig.preempt           |   9 +-
>  kernel/entry/common.c            |  17 +--
>  kernel/sched/core.c              | 180 +------------------------------
>  18 files changed, 23 insertions(+), 374 deletions(-)
>