panic: keep blinking in spite of long spin timer mode

To keep panic_timeout accuracy when running under a hypervisor, the
current implementation only spins on long time (1 second) calls to mdelay.
 That brings a good effect, but the problem is the keyboard LEDs don't
blink at all on that situation.

This patch changes to call to panic_blink_enter() between every mdelay and
keeps blinking in spite of long spin timer mode.

The time to call to mdelay is now 100ms.  Even this change will keep
panic_timeout accuracy enough when running under a hypervisor.

Signed-off-by: TAMUKI Shoichi <tamuki@linet.gr.jp>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Dmitry Torokhov <dtor@mail.ru>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 32 deletions

diff --git a/kernel/panic.c b/kernel/panic.c
index 3b16cd93fa7..3e9037ae10e 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -24,6 +24,9 @@
 #include <linux/nmi.h>
 #include <linux/dmi.h>
 
+#define PANIC_TIMER_STEP 100
+#define PANIC_BLINK_SPD 18
+
 int panic_on_oops;
 static unsigned long tainted_mask;
 static int pause_on_oops;
@@ -36,36 +39,15 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
 
 EXPORT_SYMBOL(panic_notifier_list);
 
-/* Returns how long it waited in ms */
-long (*panic_blink)(long time);
-EXPORT_SYMBOL(panic_blink);
-
-static void panic_blink_one_second(void)
+static long no_blink(int state)
 {
-	static long i = 0, end;
-
-	if (panic_blink) {
-		end = i + MSEC_PER_SEC;
-
-		while (i < end) {
-			i += panic_blink(i);
-			mdelay(1);
-			i++;
-		}
-	} else {
-		/*
-		 * When running under a hypervisor a small mdelay may get
-		 * rounded up to the hypervisor timeslice. For example, with
-		 * a 1ms in 10ms hypervisor timeslice we might inflate a
-		 * mdelay(1) loop by 10x.
-		 *
-		 * If we have nothing to blink, spin on 1 second calls to
-		 * mdelay to avoid this.
-		 */
-		mdelay(MSEC_PER_SEC);
-	}
+	return 0;
 }
 
+/* Returns how long it waited in ms */
+long (*panic_blink)(int state);
+EXPORT_SYMBOL(panic_blink);
+
 /**
  *	panic - halt the system
  *	@fmt: The text string to print
@@ -78,7 +60,8 @@ NORET_TYPE void panic(const char * fmt, ...)
 {
 	static char buf[1024];
 	va_list args;
-	long i;
+	long i, i_next = 0;
+	int state = 0;
 
 	/*
 	 * It's possible to come here directly from a panic-assertion and
@@ -117,6 +100,9 @@ NORET_TYPE void panic(const char * fmt, ...)
 
 	bust_spinlocks(0);
 
+	if (!panic_blink)
+		panic_blink = no_blink;
+
 	if (panic_timeout > 0) {
 		/*
 		 * Delay timeout seconds before rebooting the machine.
@@ -124,9 +110,13 @@ NORET_TYPE void panic(const char * fmt, ...)
 		 */
 		printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
 
-		for (i = 0; i < panic_timeout; i++) {
+		for (i = 0; i < panic_timeout * 1000; i += PANIC_TIMER_STEP) {
 			touch_nmi_watchdog();
-			panic_blink_one_second();
+			if (i >= i_next) {
+				i += panic_blink(state ^= 1);
+				i_next = i + 3600 / PANIC_BLINK_SPD;
+			}
+			mdelay(PANIC_TIMER_STEP);
 		}
 		/*
 		 * This will not be a clean reboot, with everything
@@ -152,9 +142,13 @@ NORET_TYPE void panic(const char * fmt, ...)
 	}
 #endif
 	local_irq_enable();
-	while (1) {
+	for (i = 0; ; i += PANIC_TIMER_STEP) {
 		touch_softlockup_watchdog();
-		panic_blink_one_second();
+		if (i >= i_next) {
+			i += panic_blink(state ^= 1);
+			i_next = i + 3600 / PANIC_BLINK_SPD;
+		}
+		mdelay(PANIC_TIMER_STEP);
 	}
 }