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    SubjectRe: s390 && user_enable_single_step() (Was: odd utrace testing results on s390x)
    On Thu, 7 Jan 2010 19:16:32 +0100
    Oleg Nesterov <oleg@redhat.com> wrote:

    > On 01/07, Martin Schwidefsky wrote:
    > >
    > > On Wed, 6 Jan 2010 13:08:12 -0800 (PST)
    > > Roland McGrath <roland@redhat.com> wrote:
    > >
    > > > That's what tracehook_signal_handler is for. You're both doing it yourself
    > > > in the arch code (by setting TIF_SINGLE_STEP), and then telling the generic
    > > > code to do it (by passing stepping=1 to tracehook_signal_handler).
    > >
    > > Ok, so with the full utrace the semantics of tracehook_signal_handler
    > > is more than just causing a SIGTRAP. It is an indication for a signal
    > > AND a SIGTRAP if single-stepping is active. To make both cases work we
    > > should stop setting TIF_SINGLE_STEP in do_signal and pass
    > > current->thread.per_info.single_step to tracehook_signal_handler
    > > instead of test_thread_flag(TIF_SINGLE_STEP).
    >
    > Can't understand why do we need TIF_SINGLE_STEP at all.
    >
    > Just pass current->thread.per_info.single_step to
    > tracehook_signal_handler() ?
    >
    > Oleg.
    >
    > --- a/arch/s390/kernel/signal.c
    > +++ b/arch/s390/kernel/signal.c
    > @@ -504,14 +504,8 @@ void do_signal(struct pt_regs *regs)
    > * for a normal instruction, act like we took
    > * one for the handler setup.
    > */
    > - if (current->thread.per_info.single_step)
    > - set_thread_flag(TIF_SINGLE_STEP);
    > -
    > - /*
    > - * Let tracing know that we've done the handler setup.
    > - */
    > tracehook_signal_handler(signr, &info, &ka, regs,
    > - test_thread_flag(TIF_SINGLE_STEP));
    > + current->thread.per_info.single_step);
    > }
    > return;
    > }
    >

    That is what I meant in the other mail. The patch on my local disk
    looks almost the same but it removes the comment prior to the
    TIF_SINGLE_STEP if statement as well.

    --
    blue skies,
    Martin.

    "Reality continues to ruin my life." - Calvin.



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