From: Marc Zyngier <marc.zyngier@arm.com>
To: Zenghui Yu <yuzenghui@huawei.com>,
julien.thierry@arm.com, rostedt@goodmis.org
Cc: mingo@redhat.com, catalin.marinas@arm.com, will.deacon@arm.com,
mark.rutland@arm.com, linux@armlinux.org.uk, james.morse@arm.com,
suzuki.poulose@arm.com, wanghaibin.wang@huawei.com,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH] irqchip/gic-v3: Make gic_handle_irq() notrace
Date: Fri, 29 Mar 2019 13:58:40 +0000 [thread overview]
Message-ID: <237b00d0-8a8d-ede6-91b1-c3e23e61925c@arm.com> (raw)
In-Reply-To: <1553865808-30604-1-git-send-email-yuzenghui@huawei.com>
Hi Zenghui,
On 29/03/2019 13:23, Zenghui Yu wrote:
> Enable pseudo NMI together with function_graph tracer, will lead
> the system to a hang. This is easy to reproduce,
>
> 1) Set "irqchip.gicv3_pseudo_nmi=1" on the kernel command line
> 2) echo function_graph > /sys/kernel/debug/tracing/current_tracer
>
> This patch (RFC) set gic_handle_irq() as notrace and it seems works
> fine now. But I have no idea about what the issue is exactly, and
> you can regard this patch as a report then :)
>
> Can someone give a look at it and provide some explanations ?
>
> Thanks!
>
> Cc: Julien Thierry <julien.thierry@arm.com>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
> ---
> drivers/irqchip/irq-gic-v3.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> index 15e55d3..8d0c25f 100644
> --- a/drivers/irqchip/irq-gic-v3.c
> +++ b/drivers/irqchip/irq-gic-v3.c
> @@ -487,7 +487,7 @@ static inline void gic_handle_nmi(u32 irqnr, struct pt_regs *regs)
> gic_deactivate_unhandled(irqnr);
> }
>
> -static asmlinkage void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
> +static asmlinkage notrace void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
> {
> u32 irqnr;
>
>
That's interesting. Do you have any out of tree patch that actually
makes use of the pseudo-NMI feature? Without those patches, the
behaviour should stay unchanged.
On the other hand, if you can generate pseudo-NMIs, you could end-up
tracing gic_handle_irq whilst being inside the tracing code with
interrupts being notionally disabled (and that could be pretty bad).
So, patches or no patches?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
next prev parent reply other threads:[~2019-03-29 13:58 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 13:23 [RFC PATCH] irqchip/gic-v3: Make gic_handle_irq() notrace Zenghui Yu
2019-03-29 13:58 ` Marc Zyngier [this message]
2019-03-29 14:53 ` Steven Rostedt
2019-03-29 15:35 ` Zenghui Yu
2019-03-29 15:45 ` Steven Rostedt
2019-03-29 16:19 ` Zenghui Yu
2019-03-29 15:02 ` Zenghui Yu
2019-04-02 14:00 ` Julien Thierry
2019-04-03 15:23 ` liwei (GF)
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