x86: Fix dumpstack_64 irq stack handling

Commit 2223f6f6eeaa "x86: Clean up dumpstack_64.c code" changed
the irq_stack processing a little from what it was before.
The irq_stack_end variable needed to be cleared after its first
use. By setting irq_stack to the per cpu irq_stack and passing
that to analyze_stack(), and then clearing it after it is processed,
we can get back the original behavior.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 9 deletions

diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 74c262a9b9f1..1abcb50b48ae 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -116,9 +116,9 @@ enum stack_type {
 
 static enum stack_type
 analyze_stack(int cpu, struct task_struct *task, unsigned long *stack,
-              unsigned long **stack_end, unsigned *used, char **id)
+              unsigned long **stack_end, unsigned long *irq_stack,
+              unsigned *used, char **id)
 {
-        unsigned long *irq_stack;
         unsigned long addr;
 
         addr = ((unsigned long)stack & (~(THREAD_SIZE - 1)));
@@ -130,11 +130,11 @@ analyze_stack(int cpu, struct task_struct *task, unsigned long *stack,
         if (*stack_end)
                 return STACK_IS_EXCEPTION;
 
-        *stack_end = (unsigned long *)per_cpu(irq_stack_ptr, cpu);
-        if (!*stack_end)
-                return STACK_IS_UNKNOWN;
+        if (!irq_stack)
+                return STACK_IS_NORMAL;
 
-        irq_stack = *stack_end - irq_stack_size;
+        *stack_end = irq_stack;
+        irq_stack = irq_stack - irq_stack_size;
 
         if (in_irq_stack(stack, irq_stack, *stack_end))
                 return STACK_IS_IRQ;
@@ -155,7 +155,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
 {
         const unsigned cpu = get_cpu();
         struct thread_info *tinfo;
-        unsigned long *irq_stack;
+        unsigned long *irq_stack = (unsigned long *)per_cpu(irq_stack_ptr, cpu);
         unsigned long dummy;
         unsigned used = 0;
         int graph = 0;
@@ -186,7 +186,8 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                 enum stack_type stype;
                 char *id;
 
-                stype = analyze_stack(cpu, task, stack, &stack_end, &used, &id);
+                stype = analyze_stack(cpu, task, stack, &stack_end,
+                                      irq_stack, &used, &id);
 
                 /* Default finish unless specified to continue */
                 done = 1;
@@ -226,7 +227,7 @@ void dump_trace(struct task_struct *task, struct pt_regs *regs,
                          * pointer (index -1 to end) in the IRQ stack:
                          */
                         stack = (unsigned long *) (stack_end[-1]);
-                        irq_stack = stack_end - irq_stack_size;
+                        irq_stack = NULL;
                         ops->stack(data, "EOI");
                         done = 0;
                         break;