x86, apic: Fix apic=debug boot crash

commit 05e407603e527f9d808dd3866d3a17c2ce4dfcc5 upstream.

Fix a boot crash when apic=debug is used and the APIC is
not properly initialized.

This issue appears during Xen Dom0 kernel boot but the
fix is generic and the crash could occur on real hardware
as well.

Signed-off-by: Daniel Kiper <dkiper@net-space.pl>
Cc: xen-devel@lists.xensource.com
Cc: konrad.wilk@oracle.com
Cc: jeremy@goop.org
LKML-Reference: <20100819224616.GB9967@router-fw-old.local.net-space.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index e41ed24ab26d5b51490ffa8f9a7c58a653b829d8..2b18af15b3dddeac368d715e721cd7d80bc8a140 100644 (file)
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -1728,6 +1728,8 @@ __apicdebuginit(void) print_IO_APIC(void)
                struct irq_pin_list *entry;
 
                cfg = desc->chip_data;
+               if (!cfg)
+                       continue;
                entry = cfg->irq_2_pin;
                if (!entry)
                        continue;