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From: Arjan van de Ven on 3 Jun 2010 16:10
On 6/3/2010 12:32 PM, Oleg Nesterov wrote:
> If CONFIG_FRAME_POINTER=n, print_context_stack() shouldn't neglect the
> non-reliable addresses on stack, this is all we have if dump_trace(bp)
> is called with the wrong or zero bp.
>
> For example, /proc/pid/stack doesn't work if CONFIG_FRAME_POINTER=n.
>
> This patch obviously has no effect if CONFIG_FRAME_POINTER=y, otherwise
> it reverts 1650743c "x86: don't save unreliable stack trace entries".
>

would be nice if there was a compile time thing to detect if frame
pointers are on ratehr than an ifdef.

you're now also changing the rules; until now, you would ALWAYS get a
backtrace without noise....
now that's changing quite a bit. How are various tools (like perf and
sysprof) going to cope with that?

> Also, remove the unnecessary type-cast.
>
> Signed-off-by: Oleg Nesterov<oleg(a)redhat.com>
> ---
>
> arch/x86/kernel/stacktrace.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> --- 34-rc1/arch/x86/kernel/stacktrace.c~SAVE_STACK_WO_FP 2010-06-03 18:43:27.000000000 +0200
> +++ 34-rc1/arch/x86/kernel/stacktrace.c 2010-06-03 21:29:52.000000000 +0200
> @@ -26,8 +26,10 @@ static int save_stack_stack(void *data,
> static void save_stack_address(void *data, unsigned long addr, int reliable)
> {
> struct stack_trace *trace = data;
> +#ifdef CONFIG_FRAME_POINTER
> if (!reliable)
> return;
> +#endif
> if (trace->skip> 0) {
> trace->skip--;
> return;
> @@ -39,9 +41,11 @@ static void save_stack_address(void *dat
> static void
> save_stack_address_nosched(void *data, unsigned long addr, int reliable)
> {
> - struct stack_trace *trace = (struct stack_trace *)data;
> + struct stack_trace *trace = data;
> +#ifdef CONFIG_FRAME_POINTER
> if (!reliable)
> return;
> +#endif
> if (in_sched_functions(addr))
> return;
> if (trace->skip> 0) {
>
>

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