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    SubjectRe: [PATCH 1/2] x86: make save_stack_address() !CONFIG_FRAME_POINTER friendly
    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@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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