linux-kernel - Re: [PATCH] fs/pstore: provide panic data even in suspend

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Date:	Wed, 05 Aug 2015 08:23:07 -0500
From:	Alex Elder <elder@...aro.org>
To:	check.kernel@...il.com, Anton Vorontsov <anton@...msg.org>,
	Colin Cross <ccross@...roid.com>,
	Kees Cook <keescook@...omium.org>,
	Tony Luck <tony.luck@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Petr Mladek <pmladek@...e.cz>,
	"Luis R. Rodriguez" <mcgrof@...e.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Joe Perches <joe@...ches.com>, Tejun Heo <tj@...nel.org>,
	Ethan du <duhui@...omi.com>, Linghua Gu <gulinghua@...omi.com>
CC:	linux-kernel@...r.kernel.org,
	yangdongdong <yangdongdong@...omi.com>
Subject: Re: [PATCH] fs/pstore: provide panic data even in suspend

On 08/05/2015 08:11 AM, check.kernel@...il.com wrote:
> From: yangdongdong <yangdongdong@...omi.com>
> 
> This also enables panic and oops messages which
> in suspend context to be logged into ramoops console
> buffer where it can be read back at some later point.
> 
> Signed-off-by: yangdongdong <yangdongdong@...omi.com>
> Signed-off-by: gulinghua <gulinghua@...omi.com>

I have a small comment on the code below.

					-Alex

> ---
>  fs/pstore/ram.c            | 21 +++++++++++++++++++++
>  include/linux/pstore_ram.h |  1 +
>  kernel/printk/printk.c     |  6 ++++++
>  3 files changed, 28 insertions(+)
> 
> diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
> index 6c26c4d..f84c5ab 100644
> --- a/fs/pstore/ram.c
> +++ b/fs/pstore/ram.c
> @@ -642,8 +642,28 @@ static void ramoops_register_dummy(void)
>  	}
>  }
>  
> +static int ramoops_console_notify(struct notifier_block *this,
> +		unsigned long event, void *ptr)
> +{
> +	pr_emerg("ramoops unlock console ...\n");
> +	emergency_unlock_console();
> +
> +	return 0;
> +}
> +
> +static struct notifier_block ramoop_nb = {
> +	.notifier_call = ramoops_console_notify,
> +	.priority = INT_MAX,
> +};
> +
> +static void ramoops_prepare(void)
> +{
> +	atomic_notifier_chain_register(&panic_notifier_list, &ramoop_nb);
> +}
> +
>  static int __init ramoops_init(void)
>  {
> +	ramoops_prepare();
>  	ramoops_register_dummy();
>  	return platform_driver_register(&ramoops_driver);
>  }
> @@ -654,6 +674,7 @@ static void __exit ramoops_exit(void)
>  	platform_driver_unregister(&ramoops_driver);
>  	platform_device_unregister(dummy);
>  	kfree(dummy_data);
> +	atomic_notifier_chain_unregister(&panic_notifier_list, &ramoop_nb);

I would say either wrap this atomic_notificer_chain_unregister()
call in a trivial function ramoops_unprepare(), or (preferably)
get rid of ramoops_prepare().

>  }
>  module_exit(ramoops_exit);
>  
> diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
> index 9c9d6c1..826a35b 100644
> --- a/include/linux/pstore_ram.h
> +++ b/include/linux/pstore_ram.h
> @@ -52,6 +52,7 @@ struct persistent_ram_zone {
>  	size_t old_log_size;
>  };
>  
> +extern void emergency_unlock_console(void);
>  struct persistent_ram_zone *persistent_ram_new(phys_addr_t start, size_t size,
>  			u32 sig, struct persistent_ram_ecc_info *ecc_info,
>  			unsigned int memtype);
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index cf8c242..ece645c 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2107,6 +2107,12 @@ void resume_console(void)
>  	console_unlock();
>  }
>  
> +void emergency_unlock_console(void)
> +{
> +	resume_console();
> +}
> +EXPORT_SYMBOL(emergency_unlock_console);
> +
>  /**
>   * console_cpu_notify - print deferred console messages after CPU hotplug
>   * @self: notifier struct
> 

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