Jisheng Zhang 4e90d0522a riscv: support PREEMPT_DYNAMIC with static keys ... Currently, each architecture can support PREEMPT_DYNAMIC through either static calls or static keys. To support PREEMPT_DYNAMIC on riscv, we face three choices: 1. only add static calls support to riscv As Mark pointed out in commit 99cf983cc8 ("sched/preempt: Add PREEMPT_DYNAMIC using static keys"), static keys "...should have slightly lower overhead than non-inline static calls, as this effectively inlines each trampoline into the start of its callee. This may avoid redundant work, and may integrate better with CFI schemes." So even we add static calls(without inline static calls) to riscv, static keys is still a better choice. 2. add static calls and inline static calls to riscv Per my understanding, inline static calls requires objtool support which is not easy. 3. use static keys While riscv doesn't have static calls support, it supports static keys perfectly. So this patch selects HAVE_PREEMPT_DYNAMIC_KEY to enable support for PREEMPT_DYNAMIC on riscv, so that the preemption model can be chosen at boot time. It also patches asm-generic/preempt.h, mainly to add __preempt_schedule() and __preempt_schedule_notrace() macros for PREEMPT_DYNAMIC case. Other architectures which use generic preempt.h can also benefit from this patch by simply selecting HAVE_PREEMPT_DYNAMIC_KEY to enable PREEMPT_DYNAMIC if they supports static keys. Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Link: https://lore.kernel.org/r/20230716164925.1858-1-jszhang@kernel.org Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>		2023-08-31 00:18:34 -07:00
..
boot	RISC-V Devicetrees for v6.5 Part 2	2023-06-20 23:06:54 +02:00
configs	RISC-V Patches for the 6.5 Merge Window, Part 1	2023-06-30 09:37:26 -07:00
errata	Merge patch series "riscv: some CMO alternative related clean up"	2023-07-06 10:32:38 -07:00
include	Merge patch series "riscv: support ELF format binaries in nommu mode"	2023-08-31 00:18:33 -07:00
kernel	Merge patch series "riscv: KCFI support"	2023-08-31 00:18:32 -07:00
kvm	ARM64:	2023-07-03 15:32:22 -07:00
lib	riscv: Allow to downgrade paging mode from the command line	2023-04-26 07:30:52 -07:00
mm	riscv: Move create_tmp_mapping() to init sections	2023-08-31 00:18:31 -07:00
net	Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net	2023-03-09 22:22:11 -08:00
purgatory	riscv/purgatory: Disable CFI	2023-08-23 14:16:40 -07:00
tools	riscv: Check relocations at compile time	2023-04-19 07:46:32 -07:00
Kbuild	riscv: move errata/ and kvm/ builds to arch/riscv/Kbuild	2022-06-01 22:26:32 -07:00
Kconfig	riscv: support PREEMPT_DYNAMIC with static keys	2023-08-31 00:18:34 -07:00
Kconfig.debug
Kconfig.errata	Merge patch series "RISC-V: Fixes for riscv_has_extension[un]likely()'s alternative dependency"	2023-03-29 12:26:38 -07:00
Kconfig.socs	RISC-V: make ARCH_THEAD preclude XIP_KERNEL	2023-07-05 22:21:23 +02:00
Makefile	riscv: Require FRAME_POINTER for some configurations	2023-08-23 09:07:26 -07:00
Makefile.postlink	riscv: Use --emit-relocs in order to move .rela.dyn in init	2023-04-19 07:46:33 -07:00