Re: [PATCH v5 1/2] ftrace: disable preemption when recursion locked

[Miroslav Benes]

Hi,

> diff --git a/include/linux/trace_recursion.h b/include/linux/trace_recursion.h
> index abe1a50..2bc1522 100644
> --- a/include/linux/trace_recursion.h
> +++ b/include/linux/trace_recursion.h
> @@ -135,6 +135,9 @@ static __always_inline int trace_get_context_bit(void)
>  # define do_ftrace_record_recursion(ip, pip)	do { } while (0)
>  #endif
> 
> +/*
> + * Preemption is promised to be disabled when return bit > 0.
> + */
>  static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsigned long pip,
>  							int start)
>  {
> @@ -162,11 +165,17 @@ static __always_inline int trace_test_and_set_recursion(unsigned long ip, unsign
>  	current->trace_recursion = val;
>  	barrier();
> 
> +	preempt_disable_notrace();
> +
>  	return bit;
>  }
> 
> +/*
> + * Preemption will be enabled (if it was previously enabled).
> + */
>  static __always_inline void trace_clear_recursion(int bit)
>  {
> +	preempt_enable_notrace();
>  	barrier();
>  	trace_recursion_clear(bit);
>  }

The two comments should be updated too since Steven removed the "bit == 0" 
trick.

> @@ -178,7 +187,7 @@ static __always_inline void trace_clear_recursion(int bit)
>   * tracing recursed in the same context (normal vs interrupt),
>   *
>   * Returns: -1 if a recursion happened.
> - *           >= 0 if no recursion
> + *           > 0 if no recursion.
>   */
>  static __always_inline int ftrace_test_recursion_trylock(unsigned long ip,
>  							 unsigned long parent_ip)

And this change would not be correct now.

Regards
Miroslav