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Date:   Fri, 07 Dec 2018 09:00:10 -0800 (PST)
Subject:     Re: [PATCH 4/4] RISC-V: Fix non-smp kernel boot on SMP systems
In-Reply-To: <1543870651-16669-5-git-send-email-atish.patra@wdc.com>
CC:     linux-kernel@vger.kernel.org, atish.patra@wdc.com,
        aou@eecs.berkeley.edu, daniel.lezcano@linaro.org,
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        robh+dt@kernel.org, tglx@linutronix.de, anup@brainfault.org,
        Damien.LeMoal@wdc.com
From:   Palmer Dabbelt <palmer@sifive.com>
To:     atish.patra@wdc.com
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On Mon, 03 Dec 2018 12:57:31 PST (-0800), atish.patra@wdc.com wrote:
> Currently, clocksource registration happens for an invalid cpu
> for non-smp kernels. This lead to kernel panic as cpu hotplug
> registration will fail for those cpus.
>
> Do not proceed if hartid is invalid. Take this opprtunity to
> print appropriate error strings for different failure cases.
>
> Signed-off-by: Atish Patra <atish.patra@wdc.com>
> ---
>  drivers/clocksource/riscv_timer.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/clocksource/riscv_timer.c b/drivers/clocksource/riscv_timer.c
> index 39de6e49..4af4af47 100644
> --- a/drivers/clocksource/riscv_timer.c
> +++ b/drivers/clocksource/riscv_timer.c
> @@ -108,6 +108,8 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>  	int cpuid, hartid, error;
>
>  	hartid = riscv_of_processor_hartid(n);
> +	if (hartid < 0)
> +		return hartid;

This seems like it's just hiding a bug somewhere else.  We should at least put 
out a WARN here, as I'm not sure the error will propagate anywhere useful.

>  	cpuid = riscv_hartid_to_cpuid(hartid);
>
>  	if (cpuid != smp_processor_id())
> @@ -115,14 +117,19 @@ static int __init riscv_timer_init_dt(struct device_node *n)
>
>  	/* This should be called only for boot cpu */
>  	riscv_timebase = riscv_timebase_frequency(n);
> -	clocksource_register_hz(&riscv_clocksource, riscv_timebase);
> +	error = clocksource_register_hz(&riscv_clocksource, riscv_timebase);
>
> +	if (error) {
> +		pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
> +		       error, cpuid);
> +		return error;
> +	}
>  	error = cpuhp_setup_state(CPUHP_AP_RISCV_TIMER_STARTING,
>  			 "clockevents/riscv/timer:starting",
>  			 riscv_timer_starting_cpu, riscv_timer_dying_cpu);
>  	if (error)
> -		pr_err("RISCV timer register failed [%d] for cpu = [%d]\n",
> -		       error, cpuid);
> +		pr_err("cpu hp setup state failed for RISCV timer [%d]\n",
> +		       error);
>  	return error;
>  }