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

Miroslav Benes
2021-10-26T09:35:24Z

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