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);
         }
 }