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Mon, 19 Oct 2020 13:20:41 +0100 MIME-Version: 1.0 Date: Mon, 19 Oct 2020 13:20:41 +0100 From: Marc Zyngier To: Sumit Garg Subject: Re: [PATCH v5 5/5] arm64: ipi_nmi: Add support for NMI backtrace In-Reply-To: <1602673931-28782-6-git-send-email-sumit.garg@linaro.org> References: <1602673931-28782-1-git-send-email-sumit.garg@linaro.org> <1602673931-28782-6-git-send-email-sumit.garg@linaro.org> User-Agent: Roundcube Webmail/1.4.9 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: sumit.garg@linaro.org, catalin.marinas@arm.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, tglx@linutronix.de, jason@lakedaemon.net, mark.rutland@arm.com, julien.thierry.kdev@gmail.com, dianders@chromium.org, daniel.thompson@linaro.org, jason.wessel@windriver.com, msys.mizuma@gmail.com, ito-yuichi@fujitsu.com, kgdb-bugreport@lists.sourceforge.net, linux-kernel@vger.kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201019_082045_233167_C1540EA5 X-CRM114-Status: GOOD ( 20.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mark.rutland@arm.com, daniel.thompson@linaro.org, jason@lakedaemon.net, catalin.marinas@arm.com, ito-yuichi@fujitsu.com, dianders@chromium.org, linux-kernel@vger.kernel.org, julien.thierry.kdev@gmail.com, jason.wessel@windriver.com, kgdb-bugreport@lists.sourceforge.net, tglx@linutronix.de, msys.mizuma@gmail.com, will@kernel.org, linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 > --- > 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 > > +#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 > #include > #include > +#include > #include > > #include > @@ -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... M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel