linux-kernel - Re: [PATCH 6/6] arm64: Use ftrace_graph_get_ret_stack() instead of curr_ret

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Date:   Fri, 14 Dec 2018 22:00:54 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     James Morse <james.morse@....com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-arm-kernel@...ts.infradead.org,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH 6/6] arm64: Use ftrace_graph_get_ret_stack() instead of
 curr_ret_stack

On Thu, 13 Dec 2018 17:09:35 +0000
James Morse <james.morse@....com> wrote:

> Hi Steven,
> 

> I gave this branch a spin, but I hit the WARN_ON() fairly easily:

Thanks for testing!

Can you see if this patch fixes it for you?

-- Steve

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index d4f04f0ca646..8dfd5021b933 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -246,10 +246,10 @@ unsigned long ftrace_return_to_handler(unsigned long frame_pointer)
 struct ftrace_ret_stack *
 ftrace_graph_get_ret_stack(struct task_struct *task, int idx)
 {
-	idx = current->curr_ret_stack - idx;
+	idx = task->curr_ret_stack - idx;
 
 	if (idx >= 0 && idx <= task->curr_ret_stack)
-		return &current->ret_stack[idx];
+		return &task->ret_stack[idx];
 
 	return NULL;
 }