Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint
Date	2015-12-21 18:00 +0100
Message-ID	<qIbYu-zb-13@gated-at.bofh.it> (permalink)
References	<qG8il-32J-1@gated-at.bofh.it> <qGihI-12A-3@gated-at.bofh.it> <qGrbj-6Eg-13@gated-at.bofh.it> <qI6cq-5m3-11@gated-at.bofh.it>
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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.

Why would we need to disable preemption here at all? What's the problem of
being preempted or even migrated?

Thanks,

	tglx
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Thread

[PATCH] arm64: reenable interrupt when handling ptrace breakpoint Yang Shi <yang.shi@linaro.org> - 2015-12-16 01:40 +0100
  Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint Will Deacon <will.deacon@arm.com> - 2015-12-16 12:20 +0100
    Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint "Shi, Yang" <yang.shi@linaro.org> - 2015-12-16 21:50 +0100
      Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint Will Deacon <will.deacon@arm.com> - 2015-12-21 11:50 +0100
        Re: [PATCH] arm64: reenable interrupt when handling ptrace  breakpoint Thomas Gleixner <tglx@linutronix.de> - 2015-12-21 18:00 +0100
          Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint Will Deacon <will.deacon@arm.com> - 2015-12-21 18:10 +0100
            Re: [PATCH] arm64: reenable interrupt when handling ptrace breakpoint "Shi, Yang" <yang.shi@linaro.org> - 2015-12-21 18:30 +0100

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