projects/linux·commit 8aeee85a

panic: fix panic_timeout accuracy when running on a hypervisor

8aeee85a · Anton Blanchard <[email protected]> · 2010-03-05 13:42:55 -08:00

I've had some complaints about panic_timeout being wildly innacurate on
shared processor PowerPC partitions (a 3 minute panic_timeout taking 30
minutes).

The problem is we loop on mdelay(1) and with a 1ms in 10ms hypervisor
timeslice each of these will take 10ms (ie 10x) longer.  I expect other
platforms with shared processor hypervisors will see the same issue.

This patch keeps the old behaviour if we have a panic_blink (only keyboard
LEDs right now) and does 1 second mdelays if we don't.

Signed-off-by: Anton Blanchard <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
8aeee85a29e27e043db582bf2ae8e5f42767934f
Parents
78d7d407

Changes

1 files changed · +30 −16

FileStatusAddDelContent
kernel/panic.cmodified+30−16View file

kernel/panic.c

View file
diff --git a/kernel/panic.c b/kernel/panic.c
index c787333..13d966b 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -36,15 +36,36 @@ ATOMIC_NOTIFIER_HEAD(panic_notifier_list);
EXPORT_SYMBOL(panic_notifier_list);
-static long no_blink(long time)
-{
- return 0;
-}
-
/* 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 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);
+ }
+}
+
/**
* panic - halt the system
* @fmt: The text string to print
@@ -95,9 +116,6 @@ 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.
@@ -105,11 +123,9 @@ NORET_TYPE void panic(const char * fmt, ...)
*/
printk(KERN_EMERG "Rebooting in %d seconds..", panic_timeout);
- for (i = 0; i < panic_timeout*1000; ) {
+ for (i = 0; i < panic_timeout; i++) {
touch_nmi_watchdog();
- i += panic_blink(i);
- mdelay(1);
- i++;
+ panic_blink_one_second();
}
/*
* This will not be a clean reboot, with everything
@@ -135,11 +151,9 @@ NORET_TYPE void panic(const char * fmt, ...)
}
#endif
local_irq_enable();
- for (i = 0; ; ) {
+ while (1) {
touch_softlockup_watchdog();
- i += panic_blink(i);
- mdelay(1);
- i++;
+ panic_blink_one_second();
}
}