On 25/06/2015 20:45, Andrew Jones wrote:
> spinlock torture tests made it clear that checking mmu_enabled()
> every time we call spin_lock is a bad idea. As most tests will
> want the MMU enabled the entire time, then we can inline a light
> weight "nobody disabled the mmu" check, and bail out early.
>
> Adding a light weight inlined check vs. a compile-time flag
> suggested by Paolo.
>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> lib/arm/asm/mmu-api.h | 7 ++++++-
> lib/arm/mmu.c | 9 +++++++--
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/lib/arm/asm/mmu-api.h b/lib/arm/asm/mmu-api.h
> index 12fdc57918c27..b2fc900a30add 100644
> --- a/lib/arm/asm/mmu-api.h
> +++ b/lib/arm/asm/mmu-api.h
> @@ -1,7 +1,12 @@
> #ifndef __ASMARM_MMU_API_H_
> #define __ASMARM_MMU_API_H_
> extern pgd_t *mmu_idmap;
> -extern bool mmu_enabled(void);
> +extern unsigned int mmu_disabled_cpu_count;
> +extern bool __mmu_enabled(void);
> +static inline bool mmu_enabled(void)
> +{
> + return mmu_disabled_cpu_count == 0 || __mmu_enabled();
> +}
> extern void mmu_enable(pgd_t *pgtable);
> extern void mmu_disable(void);
> extern void mmu_enable_idmap(void);
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index ad558e177dd1c..e661d4f26e4b7 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -15,8 +15,9 @@ extern unsigned long etext;
> pgd_t *mmu_idmap;
>
> static cpumask_t mmu_disabled_cpumask;
> +unsigned int mmu_disabled_cpu_count;
>
> -bool mmu_enabled(void)
> +bool __mmu_enabled(void)
> {
> int cpu = current_thread_info()->cpu;
>
> @@ -30,7 +31,9 @@ void mmu_enable(pgd_t *pgtable)
>
> asm_mmu_enable(__pa(pgtable));
> flush_tlb_all();
> - cpumask_clear_cpu(cpu, &mmu_disabled_cpumask);
> +
> + if (cpumask_test_and_clear_cpu(cpu, &mmu_disabled_cpumask))
> + --mmu_disabled_cpu_count;
> }
>
> extern void asm_mmu_disable(void);
> @@ -39,6 +42,8 @@ void mmu_disable(void)
> int cpu = current_thread_info()->cpu;
>
> cpumask_set_cpu(cpu, &mmu_disabled_cpumask);
> + ++mmu_disabled_cpu_count;
> +
> asm_mmu_disable();
> }
>
>
Applied, thanks.
Paolo
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