On Sat, 19 Jun 2021 14:29:19 +0800
Tiezhu Yang <yangtiezhu@xxxxxxxxxxx> wrote:
> If set CONFIG_FUNCTION_TRACER=y, we can use the following command to
> disable ftrace after boot up:
> echo 0 > /proc/sys/kernel/ftrace_enabled
I'd love to just remove that. It's original purpose was to stop function
tracing when the latency tracers were active. That's now done via a tracefs
option. The "ftrace_enabled" really has no use anymore.
>
> ftrace_disabled is much stronger than ftrace_enabled, introduce a new
> cmdline argument ftrace_disabled for user to control whether to disable
> ftrace when boot up.
"ftrace_disabled" is triggered when an anomaly is detected, and for the
safety of the system, ftrace shuts down. It was never meant to be a user
triggered event.
You have no rationale for this change. What's the purpose of this?
-- Steve
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@xxxxxxxxxxx>
> ---
> kernel/trace/ftrace.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 72ef4dc..a015699 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5517,6 +5517,14 @@ static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
> /* Used by function selftest to not test if filter is set */
> bool ftrace_filter_param __initdata;
>
> +static int __init set_ftrace_disabled(char *str)
> +{
> + pr_info("Set ftrace_disabled to disable ftrace\n");
> + ftrace_disabled = 1;
> + return 1;
> +}
> +__setup("ftrace_disabled", set_ftrace_disabled);
> +
> static int __init set_ftrace_notrace(char *str)
> {
> ftrace_filter_param = true;
