[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>

drivers/s390/char/con3215.c

@@ -21,6 +21,7 @@
 #include <linux/console.h>
 #include <linux/interrupt.h>
 #include <linux/err.h>
+#include <linux/reboot.h>
 
 #include <linux/slab.h>
 #include <linux/bootmem.h>
@@ -775,11 +776,11 @@ static struct tty_driver *con3215_device(struct console *c, int *index)
 }
 
 /*
- * panic() calls console_unblank before the system enters a
- * disabled, endless loop.
+ * panic() calls con3215_flush through a panic_notifier
+ * before the system enters a disabled, endless loop.
  */
 static void
-con3215_unblank(void)
+con3215_flush(void)
 {
 	struct raw3215_info *raw;
 	unsigned long flags;
@@ -790,6 +791,23 @@ con3215_unblank(void)
 	spin_unlock_irqrestore(get_ccwdev_lock(raw->cdev), flags);
 }
 
+static int con3215_notify(struct notifier_block *self,
+			  unsigned long event, void *data)
+{
+	con3215_flush();
+	return NOTIFY_OK;
+}
+
+static struct notifier_block on_panic_nb = {
+	.notifier_call = con3215_notify,
+	.priority = 0,
+};
+
+static struct notifier_block on_reboot_nb = {
+	.notifier_call = con3215_notify,
+	.priority = 0,
+};
+
 /*
  *  The console structure for the 3215 console
  */
@@ -797,7 +815,6 @@ static struct console con3215 = {
 	.name	 = "ttyS",
 	.write	 = con3215_write,
 	.device	 = con3215_device,
-	.unblank = con3215_unblank,
 	.flags	 = CON_PRINTBUFFER,
 };
 
@@ -859,6 +876,8 @@ con3215_init(void)
 		raw3215[0] = NULL;
 		return -ENODEV;
 	}
+	atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
+	register_reboot_notifier(&on_reboot_nb);
 	register_console(&con3215);
 	return 0;
 }

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;
 }

drivers/s390/char/sclp_con.c

@@ -16,6 +16,7 @@
 #include <linux/bootmem.h>
 #include <linux/termios.h>
 #include <linux/err.h>
+#include <linux/reboot.h>
 
 #include "sclp.h"
 #include "sclp_rw.h"
@@ -172,7 +173,7 @@ sclp_console_device(struct console *c, int *index)
  * will be flushed to the SCLP.
  */
 static void
-sclp_console_unblank(void)
+sclp_console_flush(void)
 {
 	unsigned long flags;
 
@@ -188,6 +189,24 @@ sclp_console_unblank(void)
 	spin_unlock_irqrestore(&sclp_con_lock, flags);
 }
 
+static int
+sclp_console_notify(struct notifier_block *self,
+			  unsigned long event, void *data)
+{
+	sclp_console_flush();
+	return NOTIFY_OK;
+}
+
+static struct notifier_block on_panic_nb = {
+	.notifier_call = sclp_console_notify,
+	.priority = 1,
+};
+
+static struct notifier_block on_reboot_nb = {
+	.notifier_call = sclp_console_notify,
+	.priority = 1,
+};
+
 /*
  * used to register the SCLP console to the kernel and to
  * give printk necessary information
@@ -197,7 +216,6 @@ static struct console sclp_console =
 	.name = sclp_console_name,
 	.write = sclp_console_write,
 	.device = sclp_console_device,
-	.unblank = sclp_console_unblank,
 	.flags = CON_PRINTBUFFER,
 	.index = 0 /* ttyS0 */
 };
@@ -241,6 +259,8 @@ sclp_console_init(void)
 	sclp_con_width_htab = 8;
 
 	/* enable printk-access to this driver */
+	atomic_notifier_chain_register(&panic_notifier_list, &on_panic_nb);
+	register_reboot_notifier(&on_reboot_nb);
 	register_console(&sclp_console);
 	return 0;
 }

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;
 }