sparc64: Handle stack trace attempts before irqstacks are setup.

Things like lockdep can try to do stack backtraces before
the irqstack blocks have been setup.  So don't try to match
their ranges so early on.

Also, remove unused variable in save_stack_trace().
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc64/kernel/kstack.h

@@ -15,6 +15,7 @@ static inline bool kstack_valid(struct thread_info *tp, unsigned long sp)
 	    sp <= (base + THREAD_SIZE - sizeof(struct sparc_stackf)))
 		return true;
 
+	if (hardirq_stack[tp->cpu]) {
 		base = (unsigned long) hardirq_stack[tp->cpu];
 		if (sp >= base &&
 		    sp <= (base + THREAD_SIZE - sizeof(struct sparc_stackf)))
@@ -23,7 +24,7 @@ static inline bool kstack_valid(struct thread_info *tp, unsigned long sp)
 		if (sp >= base &&
 		    sp <= (base + THREAD_SIZE - sizeof(struct sparc_stackf)))
 			return true;
-
+	}
 	return false;
 }
 
@@ -37,6 +38,7 @@ static inline bool kstack_is_trap_frame(struct thread_info *tp, struct pt_regs *
 	    addr <= (base + THREAD_SIZE - sizeof(*regs)))
 		goto check_magic;
 
+	if (hardirq_stack[tp->cpu]) {
 		base = (unsigned long) hardirq_stack[tp->cpu];
 		if (addr >= base &&
 		    addr <= (base + THREAD_SIZE - sizeof(*regs)))
@@ -45,7 +47,7 @@ static inline bool kstack_is_trap_frame(struct thread_info *tp, struct pt_regs *
 		if (addr >= base &&
 		    addr <= (base + THREAD_SIZE - sizeof(*regs)))
 			goto check_magic;
-
+	}
 	return false;
 
 check_magic:

arch/sparc64/kernel/stacktrace.c

@@ -9,8 +9,8 @@
 
 void save_stack_trace(struct stack_trace *trace)
 {
-	unsigned long ksp, fp, thread_base;
 	struct thread_info *tp = task_thread_info(current);
+	unsigned long ksp, fp;
 
 	stack_trace_flush();
 
@@ -20,7 +20,6 @@ void save_stack_trace(struct stack_trace *trace)
 	);
 
 	fp = ksp + STACK_BIAS;
-	thread_base = (unsigned long) tp;
 	do {
 		struct sparc_stackf *sf;
 		struct pt_regs *regs;