| Message ID | 20230716164925.1858-1-jszhang@kernel.org (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 15e062726f551e4acbe2739763d6e66562ec0a41 |
| Headers | show |
| Series | [v2] riscv: support PREEMPT_DYNAMIC with static keys | expand |
| Context | Check | Description |
|---|---|---|
| conchuod/cover_letter | success | Single patches do not need cover letters |
| conchuod/tree_selection | success | Guessed tree name to be for-next at HEAD 471aba2e4760 |
| conchuod/fixes_present | success | Fixes tag not required for -next series |
| conchuod/maintainers_pattern | success | MAINTAINERS pattern errors before the patch: 4 and now 4 |
| conchuod/verify_signedoff | success | Signed-off-by tag matches author and committer |
| conchuod/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| conchuod/build_rv64_clang_allmodconfig | success | Errors and warnings before: 2775 this patch: 2773 |
| conchuod/module_param | success | Was 0 now: 0 |
| conchuod/build_rv64_gcc_allmodconfig | success | Errors and warnings before: 15778 this patch: 15770 |
| conchuod/build_rv32_defconfig | success | Build OK |
| conchuod/dtb_warn_rv64 | success | Errors and warnings before: 3 this patch: 3 |
| conchuod/header_inline | success | No static functions without inline keyword in header files |
| conchuod/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 29 lines checked |
| conchuod/build_rv64_nommu_k210_defconfig | success | Build OK |
| conchuod/verify_fixes | success | No Fixes tag |
| conchuod/build_rv64_nommu_virt_defconfig | success | Build OK |
On Mon, Jul 17, 2023 at 12:49:25AM +0800, Jisheng Zhang wrote: > 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 99cf983cc8bc ("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> > --- > since v1: > - keep Kconfig entries sorted > - group asm-generic modifications under CONFIG_PREEMPT_DYNAMIC && > CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) > > arch/riscv/Kconfig | 1 + > include/asm-generic/preempt.h | 14 +++++++++++++- > 2 files changed, 14 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig > index 4c07b9189c86..686df6902947 100644 > --- a/arch/riscv/Kconfig > +++ b/arch/riscv/Kconfig > @@ -130,6 +130,7 @@ config RISCV > select HAVE_PERF_REGS > select HAVE_PERF_USER_STACK_DUMP > select HAVE_POSIX_CPU_TIMERS_TASK_WORK > + select HAVE_PREEMPT_DYNAMIC_KEY if !XIP_KERNEL Had a go of this, and it seems fine to me, as do the asm-generic bits seem fine from a single arch perspective. Reviewed-by: Conor Dooley <conor.dooley@microchip.com> Thanks, Conor.
Hello: This patch was applied to riscv/linux.git (for-next) by Palmer Dabbelt <palmer@rivosinc.com>: On Mon, 17 Jul 2023 00:49:25 +0800 you wrote: > 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 99cf983cc8bc ("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. > > [...] Here is the summary with links: - [v2] riscv: support PREEMPT_DYNAMIC with static keys https://git.kernel.org/riscv/c/15e062726f55 You are awesome, thank you!
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig index 4c07b9189c86..686df6902947 100644 --- a/arch/riscv/Kconfig +++ b/arch/riscv/Kconfig @@ -130,6 +130,7 @@ config RISCV select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP select HAVE_POSIX_CPU_TIMERS_TASK_WORK + select HAVE_PREEMPT_DYNAMIC_KEY if !XIP_KERNEL select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_RETHOOK if !XIP_KERNEL select HAVE_RSEQ diff --git a/include/asm-generic/preempt.h b/include/asm-generic/preempt.h index b4d43a4af5f7..51f8f3881523 100644 --- a/include/asm-generic/preempt.h +++ b/include/asm-generic/preempt.h @@ -80,9 +80,21 @@ static __always_inline bool should_resched(int preempt_offset) #ifdef CONFIG_PREEMPTION extern asmlinkage void preempt_schedule(void); -#define __preempt_schedule() preempt_schedule() extern asmlinkage void preempt_schedule_notrace(void); + +#if defined(CONFIG_PREEMPT_DYNAMIC) && defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) + +void dynamic_preempt_schedule(void); +void dynamic_preempt_schedule_notrace(void); +#define __preempt_schedule() dynamic_preempt_schedule() +#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() + +#else /* !CONFIG_PREEMPT_DYNAMIC || !CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/ + +#define __preempt_schedule() preempt_schedule() #define __preempt_schedule_notrace() preempt_schedule_notrace() + +#endif /* CONFIG_PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_KEY*/ #endif /* CONFIG_PREEMPTION */ #endif /* __ASM_PREEMPT_H */
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 99cf983cc8bc ("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> --- since v1: - keep Kconfig entries sorted - group asm-generic modifications under CONFIG_PREEMPT_DYNAMIC && CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) arch/riscv/Kconfig | 1 + include/asm-generic/preempt.h | 14 +++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-)