[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>

diff --git a/arch/x86_64/kernel/traps.c b/arch/x86_64/kernel/traps.c
index fcee07d..d345c71 100644 (file)
--- 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;
                        }
                }