[PATCH] x86_64: Reduce screen space needed by stack trace

Especially under Xen, where the console cannot be adjusted to more than 25
lines, it is fairly important that the information displayed during a panic
is as compact as possible. Below adjustments work towards that.

Signed-Off-By: Jan Beulich <jbeulich@novell.com>

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 12 insertions, 13 deletions

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index fcee07db3b68..d345c712c6ca 100644
--- a/arch/x86_64/kernel/traps.c
+++ b/arch/x86_64/kernel/traps.c
@@ -183,7 +183,6 @@ static unsigned long *in_exception_stack(unsigned cpu, unsigned long stack,
 
 void show_trace(unsigned long *stack)
 {
-        unsigned long addr;
         const unsigned cpu = safe_smp_processor_id();
         unsigned long *irqstack_end = (unsigned long *)cpu_pda(cpu)->irqstackptr;
         int i;
@@ -193,8 +192,14 @@ void show_trace(unsigned long *stack)
 
 #define HANDLE_STACK(cond) \
         do while (cond) { \
-                addr = *stack++; \
+                unsigned long addr = *stack++; \
                 if (kernel_text_address(addr)) { \
+                        if (i > 50) { \
+                                printk("\n       "); \
+                                i = 0; \
+                        } \
+                        else \
+                                i += printk(" "); \
                         /* \
                          * If the address is either in the text segment of the \
                          * kernel, or in the region which contains vmalloc'ed \
@@ -204,25 +209,19 @@ void show_trace(unsigned long *stack)
                          * out the call path that was taken. \
                          */ \
                         i += printk_address(addr); \
-                        if (i > 50) { \
-                                printk("\n       "); \
-                                i = 0; \
-                        } \
-                        else \
-                                i += printk(" "); \
                 } \
         } while (0)
 
-        for(i = 0; ; ) {
+        for(i = 11; ; ) {
                 const char *id;
                 unsigned long *estack_end;
                 estack_end = in_exception_stack(cpu, (unsigned long)stack,
                                                 &used, &id);
 
                 if (estack_end) {
-                        i += printk(" <%s> ", id);
+                        i += printk(" <%s>", id);
                         HANDLE_STACK (stack < estack_end);
-                        i += printk(" <EOE> ");
+                        i += printk(" <EOE>");
                         stack = (unsigned long *) estack_end[-2];
                         continue;
                 }
@@ -232,11 +231,11 @@ void show_trace(unsigned long *stack)
                                 (IRQSTACKSIZE - 64) / sizeof(*irqstack);
 
                         if (stack >= irqstack && stack < irqstack_end) {
-                                i += printk(" <IRQ> ");
+                                i += printk(" <IRQ>");
                                 HANDLE_STACK (stack < irqstack_end);
                                 stack = (unsigned long *) (irqstack_end[-1]);
                                 irqstack_end = NULL;
-                                i += printk(" <EOI> ");
+                                i += printk(" <EOI>");
                                 continue;
                         }
                 }