On Sat, 3 Mar 2018 10:58:23 +0100
Ingo Molnar <mi...@kernel.org> wrote:
>
> * Masami Hiramatsu <mhira...@kernel.org> wrote:
>
> > +/*
> > + * Interrupts are disabled on entry as trap3 is an interrupt gate and they
> > + * remain disabled throughout this function.
> > + */
> > +int kprobe_int3_handler(struct pt_regs *regs)
> > +{
> > + struct kprobe_ctlblk *kcb;
> > + int ret;
> > +
> > + if (user_mode(regs))
> > + return 0;
> > +
> > + /*
> > + * We don't want to be preempted for the entire
> > + * duration of kprobe processing.
> > + */
> > + preempt_disable();
> > +
> > + kcb = get_kprobe_ctlblk();
> > + ret = kprobe_int3_dispatcher(regs, kcb);
> > +
> > + if (!kprobe_ready_for_singlestep(regs))
> > + preempt_enable_no_resched();
> > +
> > + return ret;
>
> What's the point of disabling preemption, if IRQs are disabled already?
>
> There's no preemption when IRQs are off...
Ahh, right! Whole the kprobe singlestepping, IRQs are off (kprobes drops
IF from regs->flags for single stepping) so we don't need to care about
preempt count anymore...
Thank you!
--
Masami Hiramatsu <mhira...@kernel.org>
