x86/dumpstack: Fix show_stack() task pointer regression

With the following commit:

  e18bcccd1a4e ("x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder")

The task pointer argument to show_stack_log_lvl() in show_stack() was
inadvertently changed to 'current'.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: byungchul.park@lge.com
Cc: fweisbec@gmail.com
Cc: keescook@chromium.org
Cc: linux-tip-commits@vger.kernel.org
Cc: luto@amacapital.net
Cc: nilayvaish@gmail.com
Cc: rostedt@goodmis.org
Cc: tip-bot for Josh Poimboeuf <tipbot@zytor.com>
Fixes: e18bcccd1a4e ("x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder")
Link: http://lkml.kernel.org/r/20160920155340.yhewlx7vmgmov5fb@treble
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/dumpstack.c

@@ -164,7 +164,7 @@ void show_stack(struct task_struct *task, unsigned long *sp)
 	if (!sp && task == current)
 		sp = get_stack_pointer(current, NULL);
 
-	show_stack_log_lvl(current, NULL, sp, "");
+	show_stack_log_lvl(task, NULL, sp, "");
 }
 
 void show_stack_regs(struct pt_regs *regs)