[PATCH v4] fs/pstore: provide panic data even in suspend

[<check.kernel@gmail.com>]

From: Dongdong Yang <yangdongdong@xiaomi.com>

If system restart after panic, this patch 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: Dongdong Yang <yangdongdong@xiaomi.com>
Signed-off-by: Linghua Gu <gulinghua@xiaomi.com>
Signed-off-by: Hui Du <duhui@xiaomi.com>
---
 fs/pstore/ram.c        | 16 ++++++++++++++++
 include/linux/printk.h |  6 ++++++
 kernel/printk/printk.c |  6 ++++++
 3 files changed, 28 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/printk.h b/include/linux/printk.h
index a6298b2..bd043ed 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -230,6 +230,12 @@ static inline void show_regs_print_info(const char *log_lvl)
 }
 #endif
 
+/*
+ * Enables printk() before emergency_restart
+ * if we go into suspend states and run into oops.
+ */
+void emergency_unlock_console(void);
+
 extern asmlinkage void dump_stack(void) __cold;
 
 #ifndef pr_fmt
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index cf8c242..abb8af4 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)
+{
+	if (oops_in_progress && panic_timeout != 0 && console_suspended)
+		resume_console();
+}
+
 /**
  * console_cpu_notify - print deferred console messages after CPU hotplug
  * @self: notifier struct
-- 
2.5.0


v4: 
- Move declaration emergency_unlock_console to printk.h from pstore_ram.h
- Update sign-off information.

Thanks,
Dongdong Yang