From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: [PATCH v2] riscv: support PREEMPT_DYNAMIC with static keys Date: Mon, 17 Jul 2023 00:49:25 +0800 [thread overview] Message-ID: <20230716164925.1858-1-jszhang@kernel.org> (raw) 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 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 */ -- 2.40.1
WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu>, Arnd Bergmann <arnd@arndb.de> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org Subject: [PATCH v2] riscv: support PREEMPT_DYNAMIC with static keys Date: Mon, 17 Jul 2023 00:49:25 +0800 [thread overview] Message-ID: <20230716164925.1858-1-jszhang@kernel.org> (raw) 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 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 */ -- 2.40.1 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next reply other threads:[~2023-07-16 17:01 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-07-16 16:49 Jisheng Zhang [this message] 2023-07-16 16:49 ` [PATCH v2] riscv: support PREEMPT_DYNAMIC with static keys Jisheng Zhang 2023-07-24 9:59 ` Conor Dooley 2023-07-24 9:59 ` Conor Dooley 2023-08-30 13:20 ` patchwork-bot+linux-riscv 2023-08-30 13:20 ` patchwork-bot+linux-riscv
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