From: Steven Rostedt <rostedt@goodmis.org>
To: Anton Blanchard <anton@samba.org>
Cc: fweisbec@gmail.com, mingo@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] tracing/trace_stack: Fix stack trace on ppc64
Date: Mon, 30 Aug 2010 21:31:50 -0400 [thread overview]
Message-ID: <1283218310.1377.50.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <20100825013238.GE28360@kryten>
On Wed, 2010-08-25 at 11:32 +1000, Anton Blanchard wrote:
> save_stack_trace() stores the instruction pointer, not the function
> descriptor. On ppc64 the trace stack code currently dereferences the
> instruction pointer and shows 8 bytes of instructions in our backtraces:
>
> # cat /sys/kernel/debug/tracing/stack_trace
> Depth Size Location (26 entries)
> ----- ---- --------
> 0) 5424 112 0x6000000048000004
> 1) 5312 160 0x60000000ebad01b0
> 2) 5152 160 0x2c23000041c20030
> 3) 4992 240 0x600000007c781b79
> 4) 4752 160 0xe84100284800000c
> 5) 4592 192 0x600000002fa30000
> 6) 4400 256 0x7f1800347b7407e0
> 7) 4144 208 0xe89f0108f87f0070
> 8) 3936 272 0xe84100282fa30000
>
> Since we aren't dealing with function descriptors, use %pS instead of %pF
> to fix it:
>
> # cat /sys/kernel/debug/tracing/stack_trace
> Depth Size Location (26 entries)
> ----- ---- --------
> 0) 5424 112 ftrace_call+0x4/0x8
> 1) 5312 160 .current_io_context+0x28/0x74
> 2) 5152 160 .get_io_context+0x48/0xa0
> 3) 4992 240 .cfq_set_request+0x94/0x4c4
> 4) 4752 160 .elv_set_request+0x60/0x84
> 5) 4592 192 .get_request+0x2d4/0x468
> 6) 4400 256 .get_request_wait+0x7c/0x258
> 7) 4144 208 .__make_request+0x49c/0x610
> 8) 3936 272 .generic_make_request+0x390/0x434
>
> Signed-off-by: Anton Blanchard <anton@samba.org>
Thanks, I'll test this to make sure it doesn't break x86, and then push
it into a stable/-rc patch queue.
-- Steve
> ---
>
> Index: powerpc.git/kernel/trace/trace_stack.c
> ===================================================================
> --- powerpc.git.orig/kernel/trace/trace_stack.c 2010-08-25 11:03:52.337982567 +1000
> +++ powerpc.git/kernel/trace/trace_stack.c 2010-08-25 11:03:55.018371055 +1000
> @@ -249,7 +249,7 @@ static int trace_lookup_stack(struct seq
> {
> unsigned long addr = stack_dump_trace[i];
>
> - return seq_printf(m, "%pF\n", (void *)addr);
> + return seq_printf(m, "%pS\n", (void *)addr);
> }
>
> static void print_disabled(struct seq_file *m)
next prev parent reply other threads:[~2010-08-31 1:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-25 1:32 Anton Blanchard
2010-08-25 12:58 ` [tip:perf/urgent] " tip-bot for Anton Blanchard
2010-08-31 1:31 ` Steven Rostedt [this message]
2010-08-31 14:21 ` [PATCH] " Frederic Weisbecker
2010-08-31 14:58 ` Steven Rostedt
2010-08-31 15:14 ` Frederic Weisbecker
2010-08-31 17:36 ` Ingo Molnar
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