Provide a failsafe mechanism to avoid kernel spinning for ever at read_hpet_tsc
during early kernel bootup.
This failsafe mechanism was introduced in 21-rc,
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=2f7a2a79c3ebb44f8b1b7d9b4fd3a650eb69e544
But looks like the hpet split from time.c lost the commit.
This patch reintroduces the failsafe mechanism
Signed-off-by: Ravikiran Thirumalai <[email protected]>
Signed-off-by: Shai Fultheim <[email protected]>
Cc: Jack Steiner <[email protected]>
Cc: john stultz <[email protected]>
Cc: Andi Kleen <[email protected]>
Index: linux-2.6.21-rc5/arch/x86_64/kernel/hpet.c
===================================================================
--- linux-2.6.21-rc5.orig/arch/x86_64/kernel/hpet.c 2007-04-11 16:03:05.000000000 -0700
+++ linux-2.6.21-rc5/arch/x86_64/kernel/hpet.c 2007-04-11 18:49:36.000000000 -0700
@@ -191,6 +191,7 @@ int hpet_reenable(void)
#define TICK_COUNT 100000000
#define TICK_MIN 5000
+#define MAX_TRIES 5
/*
* Some platforms take periodic SMI interrupts with 5ms duration. Make sure none
@@ -198,13 +199,15 @@ int hpet_reenable(void)
*/
static void __init read_hpet_tsc(int *hpet, int *tsc)
{
- int tsc1, tsc2, hpet1;
+ int tsc1, tsc2, hpet1, i;
- do {
+ for (i = 0; i < MAX_TRIES; i++) {
tsc1 = get_cycles_sync();
hpet1 = hpet_readl(HPET_COUNTER);
tsc2 = get_cycles_sync();
- } while (tsc2 - tsc1 > TICK_MIN);
+ if (tsc2 - tsc1 > TICK_MIN)
+ break;
+ }
*hpet = hpet1;
*tsc = tsc2;
}
-
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