[PATCH v2 13/14] powerpc/64s: system reset do not trace

[Christophe Leroy]

Le 03/04/2020 à 15:26, Nicholas Piggin a écrit :
> Similarly to the previous patch, do not trace system reset. This code
> is used when there is a crash or hang, and tracing disturbs the system
> more and has been known to crash in the crash handling path.
> 
> Acked-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>
> Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> ---
>   arch/powerpc/kernel/traps.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 1845fd7e161a..ed7b7a6e2dc0 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -443,6 +443,9 @@ void system_reset_exception(struct pt_regs *regs)
>   	unsigned long hsrr0, hsrr1;
>   	bool nested = in_nmi();
>   	bool saved_hsrrs = false;
> +	u8 ftrace_enabled = local_paca->ftrace_enabled;
> +
> +	local_paca->ftrace_enabled = 0;

I predict a build failure here in the near future ...

See 
https://elixir.bootlin.com/linux/v5.6/source/arch/powerpc/kernel/head_8xx.S#L125

>   
>   	/*
>   	 * Avoid crashes in case of nested NMI exceptions. Recoverability
> @@ -524,6 +527,8 @@ void system_reset_exception(struct pt_regs *regs)
>   	if (!nested)
>   		nmi_exit();
>   
> +	local_paca->ftrace_enabled = ftrace_enabled;
> +
>   	/* What should we do here? We could issue a shutdown or hard reset. */
>   }
>   
> 

Christophe