Messages in this thread Patch in this message | | | From | Catalin Marinas <> | Subject | [RFC PATCH 6/6] ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs | Date | Tue, 29 Nov 2011 12:22:32 +0000 |
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This patch removes the __ARCH_WANT_INTERRUPTS_ON_CTXSW definition for ARMv5 and earlier processors. On such processors, the context switch requires a full cache flush. To avoid high interrupt latencies, this patch defers the mm switching is deferred to the post-lock switch hook.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Russell King <linux@arm.linux.org.uk> --- arch/arm/include/asm/mmu_context.h | 26 +++++++++++++++++++++----- arch/arm/include/asm/system.h | 9 --------- 2 files changed, 21 insertions(+), 14 deletions(-)
diff --git a/arch/arm/include/asm/mmu_context.h b/arch/arm/include/asm/mmu_context.h index 56710d8..f52729c 100644 --- a/arch/arm/include/asm/mmu_context.h +++ b/arch/arm/include/asm/mmu_context.h @@ -99,19 +99,35 @@ static inline void finish_arch_post_lock_switch(void) #else /* !CONFIG_CPU_HAS_ASID */ +#ifdef CONFIG_MMU + static inline void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk) { -#ifdef CONFIG_MMU if (unlikely(mm->context.kvm_seq != init_mm.context.kvm_seq)) __check_kvm_seq(mm); - cpu_switch_mm(mm->pgd, mm); -#endif + + /* + * Defer the cpu_switch_mm() call and continue running with the old + * mm. Since we only support UP systems on non-ASID CPUs, the old mm + * will remain valid until the finish_arch_post_lock_switch() call. + */ + set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM); } -#define init_new_context(tsk,mm) 0 +#define finish_arch_post_lock_switch \ + finish_arch_post_lock_switch +static inline void finish_arch_post_lock_switch(void) +{ + if (test_and_clear_thread_flag(TIF_SWITCH_MM)) { + struct mm_struct *mm = current->mm; + cpu_switch_mm(mm->pgd, mm); + } +} -#define finish_arch_post_lock_switch() do { } while (0) +#endif /* CONFIG_MMU */ + +#define init_new_context(tsk,mm) 0 #endif /* CONFIG_CPU_HAS_ASID */ diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h index 3daebde..ac7fade 100644 --- a/arch/arm/include/asm/system.h +++ b/arch/arm/include/asm/system.h @@ -218,15 +218,6 @@ static inline void set_copro_access(unsigned int val) } /* - * switch_mm() may do a full cache flush over the context switch, - * so enable interrupts over the context switch to avoid high - * latency. - */ -#ifndef CONFIG_CPU_HAS_ASID -#define __ARCH_WANT_INTERRUPTS_ON_CTXSW -#endif - -/* * switch_to(prev, next) should switch from task `prev' to `next' * `prev' will never be the same as `next'. schedule() itself * contains the memory barrier to tell GCC not to cache `current'.
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