ACPI: don't walk tables if ACPI was disabled

Ingo Molnar wrote:
> -tip auto-testing started triggering this spinlock corruption message
> yesterday:
>
> [    3.976213] calling  acpi_rtc_init+0x0/0xd3
> [    3.980213] ACPI Exception (utmutex-0263): AE_BAD_PARAMETER, Thread F7C50000 could not acquire Mutex [3] [20080321]
> [    3.992213] BUG: spinlock bad magic on CPU#0, swapper/1
> [    3.992213]  lock: c2508dc4, .magic: 00000000, .owner: swapper/1, .owner_cpu: 0

This is apparently because some parts of ACPI, including mutexes, are not
initialized when acpi=off is passed to the kernel.

Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
index 9b227d4dc9c9..6d18ca34b6aa 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c
@@ -336,6 +336,9 @@ static int __init acpi_rtc_init(void)
         if (acpi_disabled)
                 return 0;
 
+        if (acpi_disabled)
+                return 0;
+
         if (dev) {
                 rtc_wake_setup();
                 rtc_info.wake_on = rtc_wake_on;