From: Marc Zyngier <maz@kernel.org>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Jason Cooper <jason@lakedaemon.net>,
Mark Rutland <mark.rutland@arm.com>,
julien.thierry.kdev@gmail.com,
Douglas Anderson <dianders@chromium.org>,
Daniel Thompson <daniel.thompson@linaro.org>,
Jason Wessel <jason.wessel@windriver.com>,
Masayoshi Mizuma <msys.mizuma@gmail.com>,
ito-yuichi@fujitsu.com, kgdb-bugreport@lists.sourceforge.net,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 5/5] arm64: ipi_nmi: Add support for NMI backtrace
Date: Wed, 21 Oct 2020 11:32:00 +0100 [thread overview]
Message-ID: <ebf30013b05e8d038a63fe189f250b4b@kernel.org> (raw)
In-Reply-To: <CAFA6WYMe02J6Laa0PWDW4849KGnw8Hu2H5d6UfppeaaE4-Z0vw@mail.gmail.com>
On 2020-10-20 10:13, Sumit Garg wrote:
> On Mon, 19 Oct 2020 at 17:50, Marc Zyngier <maz@kernel.org> wrote:
>>
>> On 2020-10-14 12:12, Sumit Garg wrote:
>> > Enable NMI backtrace support on arm64 using IPI turned as an NMI
>> > leveraging pseudo NMIs support. It is now possible for users to get a
>> > backtrace of a CPU stuck in hard-lockup using magic SYSRQ.
>> >
>> > Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
>> > ---
>> > arch/arm64/include/asm/irq.h | 6 ++++++
>> > arch/arm64/kernel/ipi_nmi.c | 12 +++++++++++-
>> > 2 files changed, 17 insertions(+), 1 deletion(-)
>> >
>> > diff --git a/arch/arm64/include/asm/irq.h
>> > b/arch/arm64/include/asm/irq.h
>> > index b2b0c64..e840bf1 100644
>> > --- a/arch/arm64/include/asm/irq.h
>> > +++ b/arch/arm64/include/asm/irq.h
>> > @@ -6,6 +6,12 @@
>> >
>> > #include <asm-generic/irq.h>
>> >
>> > +#ifdef CONFIG_SMP
>> > +extern void arch_trigger_cpumask_backtrace(const cpumask_t *mask,
>> > + bool exclude_self);
>> > +#define arch_trigger_cpumask_backtrace arch_trigger_cpumask_backtrace
>> > +#endif
>> > +
>> > struct pt_regs;
>> >
>> > static inline int nr_legacy_irqs(void)
>> > diff --git a/arch/arm64/kernel/ipi_nmi.c b/arch/arm64/kernel/ipi_nmi.c
>> > index e0a9e03..e1dc19d 100644
>> > --- a/arch/arm64/kernel/ipi_nmi.c
>> > +++ b/arch/arm64/kernel/ipi_nmi.c
>> > @@ -9,6 +9,7 @@
>> > #include <linux/interrupt.h>
>> > #include <linux/irq.h>
>> > #include <linux/kgdb.h>
>> > +#include <linux/nmi.h>
>> > #include <linux/smp.h>
>> >
>> > #include <asm/nmi.h>
>> > @@ -25,12 +26,21 @@ void arch_send_call_nmi_func_ipi_mask(cpumask_t
>> > *mask)
>> > __ipi_send_mask(ipi_desc, mask);
>> > }
>> >
>> > +void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool
>> > exclude_self)
>> > +{
>> > + nmi_trigger_cpumask_backtrace(mask, exclude_self,
>> > + arch_send_call_nmi_func_ipi_mask);
>> > +}
>> > +
>> > static irqreturn_t ipi_nmi_handler(int irq, void *data)
>> > {
>> > unsigned int cpu = smp_processor_id();
>> >
>> > - ipi_kgdb_nmicallback(cpu, get_irq_regs());
>> > + if (nmi_cpu_backtrace(get_irq_regs()))
>> > + goto out;
>> >
>> > + ipi_kgdb_nmicallback(cpu, get_irq_regs());
>> > +out:
>> > return IRQ_HANDLED;
>> > }
>>
>> Can't you have *both* a request for a backtrace and a KGDB call?
>> It really shouldn't be either/or. It also outlines how well shared
>> interrupts work with edge triggered signalling...
>
> Unfortunately, NMIs doesn't seem to support shared mode [1].
You are totally missing the point: shared interrupts *cannot* work
reliably with edge signalling. What I am saying here is that you need
implement the sharing yourself in this function.
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2020-10-21 10:32 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 11:12 [PATCH v5 0/5] arm64: Add framework to turn an IPI as NMI Sumit Garg
2020-10-14 11:12 ` [PATCH v5 1/5] arm64: Add framework to turn " Sumit Garg
2020-10-15 1:15 ` Masayoshi Mizuma
2020-10-19 11:37 ` Marc Zyngier
2020-10-20 6:43 ` Sumit Garg
2020-10-20 10:08 ` Marc Zyngier
2020-10-20 11:22 ` Sumit Garg
2020-10-20 12:25 ` Daniel Thompson
2020-10-20 12:32 ` Marc Zyngier
2020-10-21 5:22 ` Sumit Garg
2020-10-21 10:27 ` Marc Zyngier
2020-10-22 11:52 ` Sumit Garg
2020-10-19 11:56 ` Marc Zyngier
2020-10-20 7:07 ` Sumit Garg
2020-10-14 11:12 ` [PATCH v5 2/5] irqchip/gic-v3: Enable support for SGIs to act as NMIs Sumit Garg
2020-10-15 1:16 ` Masayoshi Mizuma
2020-10-19 12:07 ` Marc Zyngier
2020-10-20 7:24 ` Sumit Garg
2020-10-14 11:12 ` [PATCH v5 3/5] arm64: smp: Allocate and setup IPI as NMI Sumit Garg
2020-10-15 1:16 ` Masayoshi Mizuma
2020-10-19 11:59 ` Marc Zyngier
2020-10-20 7:16 ` Sumit Garg
2020-10-14 11:12 ` [PATCH v5 4/5] arm64: kgdb: Round up cpus using " Sumit Garg
2020-10-19 12:15 ` Marc Zyngier
2020-10-20 8:51 ` Sumit Garg
2020-10-14 11:12 ` [PATCH v5 5/5] arm64: ipi_nmi: Add support for NMI backtrace Sumit Garg
2020-10-15 1:17 ` Masayoshi Mizuma
2020-10-19 12:20 ` Marc Zyngier
2020-10-20 9:13 ` Sumit Garg
2020-10-21 10:32 ` Marc Zyngier [this message]
2020-10-21 11:28 ` Sumit Garg
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