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Message-ID: <CAD=FV=UvwopskN3J_dhHsna143uG=Dh0YO=NO+9DHX-a4t7+RA@mail.gmail.com>
Date: Thu, 20 Jun 2024 15:26:43 -0700
From: Doug Anderson <dianders@...omium.org>
To: Jinjie Ruan <ruanjinjie@...wei.com>
Cc: catalin.marinas@....com, will@...nel.org, mark.rutland@....com,
swboyd@...omium.org, sumit.garg@...aro.org, frederic@...nel.org,
scott@...amperecomputing.com, misono.tomohiro@...itsu.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: smp: Fix missing IPI statistics
Hi,
On Wed, Jun 19, 2024 at 11:31 PM Jinjie Ruan <ruanjinjie@...wei.com> wrote:
>
> commit 83cfac95c018 ("genirq: Allow interrupts to be excluded from
> /proc/interrupts") is to avoid IPIs appear twice in /proc/interrupts.
> But the commit 331a1b3a836c ("arm64: smp: Add arch support for backtrace
> using pseudo-NMI") and commit 2f5cd0c7ffde("arm64: kgdb: Implement
> kgdb_roundup_cpus() to enable pseudo-NMI roundup") set CPU_BACKTRACE and
> KGDB_ROUNDUP IPIs "IRQ_HIDDEN" flag but not show them in
> arch_show_interrupts(), which cause the interrupt kstat_irqs accounting
> is missing in display.
>
> Before this patch, CPU_BACKTRACE and KGDB_ROUNDUP IPIs are missing:
> / # cat /proc/interrupts
> CPU0 CPU1 CPU2 CPU3
> 11: 466 600 309 332 GICv3 27 Level arch_timer
> 13: 24 0 0 0 GICv3 33 Level uart-pl011
> 15: 64 0 0 0 GICv3 78 Edge virtio0
> 16: 0 0 0 0 GICv3 79 Edge virtio1
> 17: 0 0 0 0 GICv3 34 Level rtc-pl031
> 18: 3 3 3 3 GICv3 23 Level arm-pmu
> 19: 0 0 0 0 9030000.pl061 3 Edge GPIO Key Poweroff
> IPI0: 7 14 9 26 Rescheduling interrupts
> IPI1: 354 93 233 255 Function call interrupts
> IPI2: 0 0 0 0 CPU stop interrupts
> IPI3: 0 0 0 0 CPU stop (for crash dump) interrupts
> IPI4: 0 0 0 0 Timer broadcast interrupts
> IPI5: 1 0 0 0 IRQ work interrupts
> Err: 0
>
> After this pacth, CPU_BACKTRACE and KGDB_ROUNDUP IPIs are displayed:
> / # cat /proc/interrupts
> CPU0 CPU1 CPU2 CPU3
> 11: 393 281 532 449 GICv3 27 Level arch_timer
> 13: 15 0 0 0 GICv3 33 Level uart-pl011
> 15: 64 0 0 0 GICv3 78 Edge virtio0
> 16: 0 0 0 0 GICv3 79 Edge virtio1
> 17: 0 0 0 0 GICv3 34 Level rtc-pl031
> 18: 2 2 2 2 GICv3 23 Level arm-pmu
> 19: 0 0 0 0 9030000.pl061 3 Edge GPIO Key Poweroff
> IPI0: 11 19 4 23 Rescheduling interrupts
> IPI1: 279 347 222 72 Function call interrupts
> IPI2: 0 0 0 0 CPU stop interrupts
> IPI3: 0 0 0 0 CPU stop (for crash dump) interrupts
> IPI4: 0 0 0 0 Timer broadcast interrupts
> IPI5: 1 0 0 1 IRQ work interrupts
> IPI6: 0 0 0 0 CPU backtrace interrupts
> IPI7: 0 0 0 0 KGDB roundup interrupts
> Err: 0
>
> Fixes: 331a1b3a836c ("arm64: smp: Add arch support for backtrace using pseudo-NMI")
> Signed-off-by: Jinjie Ruan <ruanjinjie@...wei.com>
> Suggested-by: Doug Anderson <dianders@...omium.org>
> ---
> v2:
> - Report them in arch_show_interrupts().
> - Add suggested-by.
> - Update the commit message.
> ---
> arch/arm64/kernel/smp.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
Personally I don't find a ton of value in having the "CPU backtrace
interrupts" and "KGDB roundup interrupts" reported, but I agree that
if someone does find value in having them reported that this is the
best way. I guess that means a light:
Reviewed-by: Douglas Anderson <dianders@...omium.org>
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