On Thu, Jun 25, 2015 at 06:12:18PM +0200, Andrew Jones wrote:
> spinlock torture tests made it clear that checking mmu_enabled()
> every time we call spin_lock is a bad idea.
why a bad idea? Does it break, is it slow?
> As most tests will
> want the MMU enabled the entire time, then just hard code
> mmu_enabled() to true. Tests that want to play with the MMU can
> be compiled with CONFIG_MAY_DISABLE_MMU to get the actual check
> back.
If we don't care about performance, why this added complexity?
>
> Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> ---
> lib/arm/asm/mmu-api.h | 4 ++++
> lib/arm/mmu.c | 3 +++
> 2 files changed, 7 insertions(+)
>
> diff --git a/lib/arm/asm/mmu-api.h b/lib/arm/asm/mmu-api.h
> index 68dc707d67241..1a4d91163c398 100644
> --- a/lib/arm/asm/mmu-api.h
> +++ b/lib/arm/asm/mmu-api.h
> @@ -1,7 +1,11 @@
> #ifndef __ASMARM_MMU_API_H_
> #define __ASMARM_MMU_API_H_
> extern pgd_t *mmu_idmap;
> +#ifdef CONFIG_MAY_DISABLE_MMU
> extern bool mmu_enabled(void);
> +#else
> +#define mmu_enabled() (1)
> +#endif
> extern void mmu_set_enabled(void);
> extern void mmu_enable(pgd_t *pgtable);
> extern void mmu_enable_idmap(void);
> diff --git a/lib/arm/mmu.c b/lib/arm/mmu.c
> index 732000a8eb088..405717b6332bf 100644
> --- a/lib/arm/mmu.c
> +++ b/lib/arm/mmu.c
> @@ -15,11 +15,14 @@ extern unsigned long etext;
> pgd_t *mmu_idmap;
>
> static cpumask_t mmu_enabled_cpumask;
> +
> +#ifdef CONFIG_MAY_DISABLE_MMU
> bool mmu_enabled(void)
> {
> struct thread_info *ti = current_thread_info();
> return cpumask_test_cpu(ti->cpu, &mmu_enabled_cpumask);
> }
> +#endif
>
> void mmu_set_enabled(void)
> {
> --
> 2.4.3
>
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