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Date:	Wed,  5 Aug 2015 21:56:07 +0800
From:	<check.kernel@...il.com>
To:	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>, Alex Elder <elder@...aro.org>,
	"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: [PATCH] ramoops: provide panic data even in suspend

From: yangdongdong <yangdongdong@...omi.com>

Good comments. It is valuable for code readable. Here is not necessary wrap atomic_notifier_chain_register into ramoops_prepare. The updated patch as below:

>From 5ec3976e2b55dfaf8bd1bc88c5a9c05762148fef Mon Sep 17 00:00:00 2001
From: yangdongdong <yangdongdong@...omi.com>
Date: Wed, 5 Aug 2015 18:51:17 +0800
Subject: [PATCH] ramoops: provide panic data even in suspend

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>
---
 fs/pstore/ram.c            | 16 ++++++++++++++++
 include/linux/pstore_ram.h |  1 +
 kernel/printk/printk.c     |  6 ++++++
 3 files changed, 23 insertions(+)

diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6c26c4d..3d981a1 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -642,8 +642,23 @@ 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 int __init ramoops_init(void)
 {
+	atomic_notifier_chain_register(&panic_notifier_list, &ramoop_nb);
 	ramoops_register_dummy();
 	return platform_driver_register(&ramoops_driver);
 }
@@ -654,6 +669,7 @@ 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);
 }
 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
-- 
2.5.0

Thanks,
Andy

-----邮件原件-----
发件人: Alex Elder [mailto:elder@...aro.org]
发送时间: 2015年8月5日 21:23
收件人: check.kernel@...il.com; Anton Vorontsov; Colin Cross; Kees Cook; Tony Luck; Andrew Morton; Petr Mladek; Luis R. Rodriguez; Peter Hurley; Joe Perches; Tejun Heo; 杜慧; 顾凌华
抄送: linux-kernel@...r.kernel.org; 杨冬东
主题: 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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