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panic: fix panic_timeout accuracy when running on a hypervisor 

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 <anton@samba.org>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Anton Blanchard 2010-03-05 13:42:55 -08:00 committed by Linus Torvalds
parent 78d7d407b6
commit 8aeee85a29
1 changed files with 30 additions and 16 deletions
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46
kernel/panic.c
View File

@ -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();
}
}