[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, 18 insertions, 8 deletions

diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c
index ad51738c4261..9854f19f5e62 100644
--- a/drivers/s390/char/sclp_vt220.c
+++ b/drivers/s390/char/sclp_vt220.c
@@ -24,6 +24,8 @@
 #include <linux/bootmem.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
+#include <linux/reboot.h>
+
 #include <asm/uaccess.h>
 #include "sclp.h"
 
@@ -743,24 +745,30 @@ sclp_vt220_con_device(struct console *c, int *index)
         return sclp_vt220_driver;
 }
 
-/*
- * This routine is called from panic when the kernel is going to give up.
- * We have to make sure that all buffers will be flushed to the SCLP.
- * Note that this function may be called from within an interrupt context.
- */
-static void
-sclp_vt220_con_unblank(void)
+static int
+sclp_vt220_notify(struct notifier_block *self,
+                          unsigned long event, void *data)
 {
         __sclp_vt220_flush_buffer();
+        return NOTIFY_OK;
 }
 
+static struct notifier_block on_panic_nb = {
+        .notifier_call = sclp_vt220_notify,
+        .priority = 1,
+};
+
+static struct notifier_block on_reboot_nb = {
+        .notifier_call = sclp_vt220_notify,
+        .priority = 1,
+};
+
 /* Structure needed to register with printk */
 static struct console sclp_vt220_console =
 {
         .name = SCLP_VT220_CONSOLE_NAME,
         .write = sclp_vt220_con_write,
         .device = sclp_vt220_con_device,
-        .unblank = sclp_vt220_con_unblank,
         .flags = CON_PRINTBUFFER,
         .index = SCLP_VT220_CONSOLE_INDEX
 };
@@ -776,6 +784,8 @@ sclp_vt220_con_init(void)
         if (rc)
                 return rc;
         /* Attach linux console */
+        atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
+        register_reboot_notifier(&on_reboot_nb);
         register_console(&sclp_vt220_console);
         return 0;
 }