Re: [PATCH 5/8] x86,tracing: Mark debug_stack_{set_zero,reset)() notrace

Steven Rostedt
2020-02-12T14:25:43Z

On Wed, 12 Feb 2020 10:32:15 +0100
Peter Zijlstra <peterz@infradead.org> wrote:

> Because do_nmi() must not call into tracing outside of
> nmi_enter()/nmi_exit(), these functions must be notrace.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
> arch/x86/kernel/cpu/common.c | 4 ++--
> arch/x86/kernel/nmi.c | 6 ++++++
> 2 files changed, 8 insertions(+), 2 deletions(-)
>
> --- a/arch/x86/kernel/cpu/common.c
> +++ b/arch/x86/kernel/cpu/common.c

This entire file is notrace:

arch/x86/kernel/cpu/Makefile:

CFLAGS_REMOVE_common.o = -pg

-- Steve

> @@ -1690,14 +1690,14 @@ void syscall_init(void)
> DEFINE_PER_CPU(int, debug_stack_usage);
> DEFINE_PER_CPU(u32, debug_idt_ctr);
>
> -void debug_stack_set_zero(void)
> +void notrace debug_stack_set_zero(void)
> {
> this_cpu_inc(debug_idt_ctr);
> load_current_idt();
> }
> NOKPROBE_SYMBOL(debug_stack_set_zero);
>
> -void debug_stack_reset(void)
> +void notrace debug_stack_reset(void)
> {
> if (WARN_ON(!this_cpu_read(debug_idt_ctr)))
> return;
> --- a/arch/x86/kernel/nmi.c
> +++ b/arch/x86/kernel/nmi.c
> @@ -534,6 +534,9 @@ do_nmi(struct pt_regs *regs, long error_
> }
> #endif
>
> + /*
> + * It is important that no tracing happens before nmi_enter()!
> + */
> nmi_enter();
>
> inc_irq_stat(__nmi_count);
> @@ -542,6 +545,9 @@ do_nmi(struct pt_regs *regs, long error_
> default_do_nmi(regs);
>
> nmi_exit();
> + /*
> + * No tracing after nmi_exit()!
> + */
>
> #ifdef CONFIG_X86_64
> if (unlikely(this_cpu_read(update_debug_stack))) {
>