Re: [PATCH] kernel: context_tracking: use extern function insteadof static inline function for user_enter/exit()

From: Steven Rostedt
Date: Wed Oct 23 2013 - 06:47:37 EST


On Wed, 2013-10-23 at 18:38 +0800, Chen Gang wrote:

>
> Signed-off-by: Chen Gang <gang.chen@xxxxxxxxxxx>
> ---
> include/linux/context_tracking.h | 14 ++------------
> kernel/context_tracking.c | 12 ++++++++++++
> 2 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
> index 1581587..bf220f7 100644
> --- a/include/linux/context_tracking.h
> +++ b/include/linux/context_tracking.h
> @@ -10,23 +10,13 @@
> #ifdef CONFIG_CONTEXT_TRACKING
> extern void context_tracking_cpu_set(int cpu);
>
> +extern void user_enter(void);
> +extern void user_exit(void);
> extern void context_tracking_user_enter(void);
> extern void context_tracking_user_exit(void);
> extern void __context_tracking_task_switch(struct task_struct *prev,
> struct task_struct *next);
>
> -static inline void user_enter(void)
> -{
> - if (static_key_false(&context_tracking_enabled))
> - context_tracking_user_enter();
> -
> -}
> -static inline void user_exit(void)
> -{
> - if (static_key_false(&context_tracking_enabled))
> - context_tracking_user_exit();
> -}
> -
> static inline enum ctx_state exception_enter(void)
> {
> enum ctx_state prev_ctx;
> diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
> index 013161f..c03d0d6 100644
> --- a/kernel/context_tracking.c
> +++ b/kernel/context_tracking.c
> @@ -29,6 +29,18 @@ EXPORT_SYMBOL_GPL(context_tracking_enabled);
> DEFINE_PER_CPU(struct context_tracking, context_tracking);
> EXPORT_SYMBOL_GPL(context_tracking);
>
> +void user_enter(void)
> +{
> + if (static_key_false(&context_tracking_enabled))
> + context_tracking_user_enter();
> +}
> +
> +void user_exit(void)
> +{
> + if (static_key_false(&context_tracking_enabled))
> + context_tracking_user_exit();
> +}
> +
> void context_tracking_cpu_set(int cpu)
> {
> if (!per_cpu(context_tracking.active, cpu)) {

Ug, you just put an unneeded function call into a fast path because of a
failure with a particular arch.

If you need the assembly to call this code, then make yourself a wrapper
function to call that does the user_enter/exit() calls.

void arch_user_enter(void)
{
user_enter();
}

-- Steve


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