Messages in this thread Patch in this message | | | From | Mark Rutland <> | Subject | [PATCH 6/6] arm64: support PREEMPT_DYNAMIC | Date | Tue, 9 Nov 2021 17:24:08 +0000 |
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This patch enables support for PREEMPT_DYNAMIC on arm64, using static keys to disable the out-of-line forms of the preemption functions. This side-steps a number of pain points highlighted with static calls, and I expect the overhead to be similar (and hopefully lower in some cases) than would be the case for non-inlined static calls, by virtue of effectively inlining the trampolines into the callees.
Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Frederic Weisbecker <frederic@kernel.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Will Deacon <will@kernel.org> --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/preempt.h | 16 ++++++++++++++-- arch/arm64/kernel/entry-common.c | 9 +++++++++ 3 files changed, 24 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index c4207cf9bb17..928b710465ce 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -191,6 +191,7 @@ config ARM64 select HAVE_PERF_EVENTS select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP + select HAVE_PREEMPT_DYNAMIC_KEY select HAVE_REGS_AND_STACK_ACCESS_API select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_FUNCTION_ARG_ACCESS_API diff --git a/arch/arm64/include/asm/preempt.h b/arch/arm64/include/asm/preempt.h index e83f0982b99c..73623f719d7e 100644 --- a/arch/arm64/include/asm/preempt.h +++ b/arch/arm64/include/asm/preempt.h @@ -80,10 +80,22 @@ static inline bool should_resched(int preempt_offset) } #ifdef CONFIG_PREEMPTION +#ifdef CONFIG_PREEMPT_DYNAMIC + +DECLARE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); +void dynamic_preempt_schedule(void); +#define __preempt_schedule() dynamic_preempt_schedule() +void dynamic_preempt_schedule_notrace(void); +#define __preempt_schedule_notrace() dynamic_preempt_schedule_notrace() + +#else + void preempt_schedule(void); -#define __preempt_schedule() preempt_schedule() +#define __preempt_schedule() preempt_schedule() void preempt_schedule_notrace(void); -#define __preempt_schedule_notrace() preempt_schedule_notrace() +#define __preempt_schedule_notrace() preempt_schedule_notrace() + +#endif #endif /* CONFIG_PREEMPTION */ #endif /* __ASM_PREEMPT_H */ diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index f7408edf8571..f096678dd580 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -220,10 +220,19 @@ static void noinstr arm64_exit_el1_dbg(struct pt_regs *regs) lockdep_hardirqs_on(CALLER_ADDR0); } +#ifdef CONFIG_PREEMPT_DYNAMIC +DEFINE_STATIC_KEY_TRUE(sk_dynamic_irqentry_exit_cond_resched); +#endif + static void __sched arm64_preempt_schedule_irq(void) { lockdep_assert_irqs_disabled(); +#ifdef CONFIG_PREEMPT_DYNAMIC + if (!static_branch_unlikely(&sk_dynamic_irqentry_exit_cond_resched)) + return; +#endif + /* * DAIF.DA are cleared at the start of IRQ/FIQ handling, and when GIC * priority masking is used the GIC irqchip driver will clear DAIF.IF -- 2.11.0
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