linux-kernel - Re: [PATCH 1/1] arch: arm64: process: Unlock console after SMP stopped

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Message-ID: <20190409142112.mcvzdxigjfxnzrb4@shell.armlinux.org.uk>
Date:   Tue, 9 Apr 2019 15:21:12 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Jinyoung Park <gt.jypark@...il.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Alex Van Brunt <avanbrunt@...dia.com>,
        Ketan Patil <ketanp@...dia.com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/1] arch: arm64: process: Unlock console after SMP
 stopped

On Tue, Apr 09, 2019 at 11:17:14PM +0900, Jinyoung Park wrote:
> If the console lock is held by other CPU running while the system is
> restarting or shutting down, the Kernel messages in the printk log buffer
> can not be printed out to the console drivers. The Kernel messages can be
> lost or messed up.
> This change calls console_unlock after SMP stopped to flush the kernel
> messages in the printk log buffer to the console drivers.

I think you need to explain how we can get to each of these points
while the current CPU is holding the console lock - and why this is
only an ARM64 problem (or why you are only fixing this on ARM64 and
not any of the other architectures.)

> 
> Signed-off-by: Jinyoung Park <jinyoungp@...dia.com>
> ---
>  arch/arm64/kernel/process.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index 3767fb21a5b8..d629a75c7602 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -49,6 +49,7 @@
>  #include <trace/events/power.h>
>  #include <linux/percpu.h>
>  #include <linux/thread_info.h>
> +#include <linux/console.h>
> 
>  #include <asm/alternative.h>
>  #include <asm/arch_gicv3.h>
> @@ -164,6 +165,7 @@ void machine_halt(void)
>  {
>   local_irq_disable();
>   smp_send_stop();
> + console_unlock();
>   while (1);
>  }
> 
> @@ -177,6 +179,7 @@ void machine_power_off(void)
>  {
>   local_irq_disable();
>   smp_send_stop();
> + console_unlock();
>   if (pm_power_off)
>   pm_power_off();
>  }
> @@ -195,6 +198,7 @@ void machine_restart(char *cmd)
>   /* Disable interrupts first */
>   local_irq_disable();
>   smp_send_stop();
> + console_unlock();
> 
>   /*
>   * UpdateCapsule() depends on the system being reset via
> -- 
> 2.19.0
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

-- 
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