On Tue, Jan 12, 2016 at 11:59:54AM -0800, Shi, Yang wrote:
> On 12/21/2015 9:00 AM, Will Deacon wrote:
> >On Mon, Dec 21, 2015 at 05:51:22PM +0100, Thomas Gleixner wrote:
> >>On Mon, 21 Dec 2015, Will Deacon wrote:
> >>>+static void send_user_sigtrap(int si_code)
> >>>+{
> >>>+ struct pt_regs *regs = current_pt_regs();
> >>>+ siginfo_t info = {
> >>>+ .si_signo = SIGTRAP,
> >>>+ .si_errno = 0,
> >>>+ .si_code = si_code,
> >>>+ .si_addr = (void __user *)instruction_pointer(regs),
> >>>+ };
> >>>+
> >>>+ if (WARN_ON(!user_mode(regs)))
> >>>+ return;
> >>>+
> >>>+ preempt_disable();
> >>
> >>That doesn't work on RT either. force_sig_info() takes task->sighand->siglock,
> >>which is a 'sleeping' spinlock on RT.
> >
> >Ah, I missed that :/
> >
> >>Why would we need to disable preemption here at all? What's the problem of
> >>being preempted or even migrated?
> >
> >There *might* not be a problem, I'm just really nervous about changing
> >the behaviour on the debug path and subtly changing how ptrace behaves.
> >
> >My worry was that you could somehow get back into the tracer, and it
> >could remove a software breakpoint in the knowledge that it wouldn't
> >see any future (spurious) SIGTRAPs for that location.
> >
> >Without a concrete example, however, I guess I'll bite the bullet and
> >enable irqs across the call to force_sig_info, since there is clearly a
> >real issue here on RT.
>
> This might be buried in email storm during the holiday. Just want to double
> check the status. I'm supposed there is no objection for getting it merged
> in upstream?
Sorry, when you replied with:
> I think we could just extend the "signal delay send" approach from x86-64
> to arm64, which is currently used by x86-64 on -rt kernel only.
I understood that you were going to fix -rt, so I dropped this pending
anything more from you.
What's the plan?
Will
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
