[S390] console flush on panic / reboot

The s390 console drivers use the unblank callback of the console
structure to flush the console buffer. In case of a panic or a
reboot the CPU doing the callback can block on the console i/o.
The other CPUs in the system continue to work. For panic this is
not a good idea.

Replace the unblank callback with proper panic/reboot notifier.
These get called after all but one CPU have been stopped.

Signed-off-by: Holger Smolinski <Holger.Smolinski@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

1 files changed, 23 insertions, 4 deletions

diff --git a/drivers/s390/char/con3270.c b/drivers/s390/char/con3270.c
index 3c07974886ed..d028d2ee83dd 100644
--- a/drivers/s390/char/con3270.c
+++ b/drivers/s390/char/con3270.c
@@ -15,6 +15,7 @@
 #include <linux/list.h>
 #include <linux/types.h>
 #include <linux/err.h>
+#include <linux/reboot.h>
 
 #include <asm/ccwdev.h>
 #include <asm/cio.h>
@@ -528,11 +529,11 @@ con3270_wait_write(struct con3270 *cp)
 }
 
 /*
- * panic() calls console_unblank before the system enters a
- * disabled, endless loop.
+ * panic() calls con3270_flush through a panic_notifier
+ * before the system enters a disabled, endless loop.
  */
 static void
-con3270_unblank(void)
+con3270_flush(void)
 {
         struct con3270 *cp;
         unsigned long flags;
@@ -554,6 +555,23 @@ con3270_unblank(void)
         spin_unlock_irqrestore(&cp->view.lock, flags);
 }
 
+static int con3270_notify(struct notifier_block *self,
+                          unsigned long event, void *data)
+{
+        con3270_flush();
+        return NOTIFY_OK;
+}
+
+static struct notifier_block on_panic_nb = {
+        .notifier_call = con3270_notify,
+        .priority = 0,
+};
+
+static struct notifier_block on_reboot_nb = {
+        .notifier_call = con3270_notify,
+        .priority = 0,
+};
+
 /*
  *  The console structure for the 3270 console
  */
@@ -561,7 +579,6 @@ static struct console con3270 = {
         .name    = "tty3270",
         .write   = con3270_write,
         .device  = con3270_device,
-        .unblank = con3270_unblank,
         .flags   = CON_PRINTBUFFER,
 };
 
@@ -623,6 +640,8 @@ con3270_init(void)
         condev->cline->len = 0;
         con3270_create_status(condev);
         condev->input = alloc_string(&condev->freemem, 80);
+        atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
+        register_reboot_notifier(&on_reboot_nb);
         register_console(&con3270);
         return 0;
 }