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Re: [PATCH v3] arm: Fix backtrace generation when IPI is masked

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On Tue, 15 Sep 2015, Daniel Thompson wrote:

> Currently on ARM when <SysRq-L> is triggered from an interrupt handler
> (e.g. a SysRq issued using UART or kbd) the main CPU will wedge for ten
> seconds with interrupts masked before issuing a backtrace for every CPU
> except itself.
> 
> The new backtrace code introduced by commit 96f0e00378d4 ("ARM: add
> basic support for on-demand backtrace of other CPUs") does not work
> correctly when run from an interrupt handler because IPI_CPU_BACKTRACE
> is used to generate the backtrace on all CPUs but cannot preempt the
> current calling context.
> 
> This can be fixed by detecting that the calling context cannot be
> preempted and issuing the backtrace directly in this case. Issuing
> directly leaves us without any pt_regs to pass to nmi_cpu_backtrace()
> so we also modify the generic code to call dump_stack() when its
> argument is NULL.
> 
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

For the genric part.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
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[PATCH] arm: Fix backtrace generation when IPI is masked Daniel Thompson <daniel.thompson@linaro.org> - 2015-09-14 11:20 +0200
  [PATCH v2] arm: Fix backtrace generation when IPI is masked Daniel Thompson <daniel.thompson@linaro.org> - 2015-09-15 13:10 +0200
    Re: [PATCH v2] arm: Fix backtrace generation when IPI is masked Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-15 13:40 +0200
      Re: [PATCH v2] arm: Fix backtrace generation when IPI is masked Daniel Thompson <daniel.thompson@linaro.org> - 2015-09-15 15:20 +0200
        Re: [PATCH v2] arm: Fix backtrace generation when IPI is masked Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-09-15 15:50 +0200
  [PATCH v3] arm: Fix backtrace generation when IPI is masked Daniel Thompson <daniel.thompson@linaro.org> - 2015-09-15 16:50 +0200
    Re: [PATCH v3] arm: Fix backtrace generation when IPI is masked "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2015-09-16 04:50 +0200
    Re: [PATCH v3] arm: Fix backtrace generation when IPI is masked Thomas Gleixner <tglx@linutronix.de> - 2015-09-22 13:10 +0200
    Re: [PATCH v3] arm: Fix backtrace generation when IPI is masked Russell King - ARM Linux <linux@arm.linux.org.uk> - 2015-10-03 17:50 +0200

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