[PATCH 1/5] x86: don't show trace beyond show_stack(NULL, NULL)

[Tejun Heo <tj@kernel.org>]

show_stack(current or NULL, NULL) is used to print the backtrace of
the current task.  As trace beyond the function itself isn't of much
interest to anyone, don't show it by determining sp and bp in
show_stack()'s frame and passing them to show_stack_log_lvl().

This brings show_stack(NULL, NULL)'s behavior in line with
dump_stack().

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 arch/x86/kernel/dumpstack.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index c8797d5..dd1a7c3 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -176,7 +176,19 @@ void show_trace(struct task_struct *task, struct pt_regs *regs,
 
 void show_stack(struct task_struct *task, unsigned long *sp)
 {
-	show_stack_log_lvl(task, NULL, sp, 0, "");
+	unsigned long bp = 0;
+	unsigned long stack;
+
+	/*
+	 * Stack frames below this one aren't interesting.  Don't show them
+	 * if we're printing for %current.
+	 */
+	if (!sp && (!task || task == current)) {
+		sp = &stack;
+		bp = stack_frame(current, NULL);
+	}
+
+	show_stack_log_lvl(task, NULL, sp, bp, "");
 }
 
 /*
-- 
1.8.1.4