[PATCH] fs/pstore: provide panic data even in suspend

[<check.kernel@gmail.com>]

From: yangdongdong <yangdongdong@xiaomi.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@xiaomi.com>
Signed-off-by: gulinghua <gulinghua@xiaomi.com>
---
 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);
 }
 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