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Date: Thu, 26 Mar 2020 22:53:57 +0530
From: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Subject: Re: [PATCH v2 12/12] powerpc/64s: system reset do not trace
To: linuxppc-dev@lists.ozlabs.org, Nicholas Piggin <npiggin@gmail.com>
References: <20200325103410.157573-1-npiggin@gmail.com>
 <20200325103410.157573-13-npiggin@gmail.com>
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Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>,
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Nicholas Piggin wrote:
> 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.
>=20
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  arch/powerpc/kernel/traps.c | 5 +++++
>  1 file changed, 5 insertions(+)

For the ftrace bits:
Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>

>=20
> 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 =3D in_nmi();
>  	bool saved_hsrrs =3D false;
> +	u8 ftrace_enabled =3D local_paca->ftrace_enabled;
> +
> +	local_paca->ftrace_enabled =3D 0;
> =20
>  	/*
>  	 * 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();
> =20
> +	local_paca->ftrace_enabled =3D ftrace_enabled;
> +

I suppose we could add helpers to save/restore the state. But, since we=20
only have these two users as of now, we can revisit that if the need=20
arises.


- Naveen