From: Jinjie Ruan <ruanjinjie@huawei.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: <dianders@chromium.org>, <mhocko@suse.com>,
<akpm@linux-foundation.org>, <maz@kernel.org>,
<vschneid@redhat.com>, <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ARM: smp: Fix missing backtrace IPI statics
Date: Fri, 2 Aug 2024 09:39:33 +0800 [thread overview]
Message-ID: <c55bbffe-9144-f787-eb70-8328be5cfe7c@huawei.com> (raw)
In-Reply-To: <Zqu5ck+Ik8KlzE0O@shell.armlinux.org.uk>
On 2024/8/2 0:36, Russell King (Oracle) wrote:
> On Thu, Aug 01, 2024 at 05:40:22PM +0800, Jinjie Ruan wrote:
>> It is similar to ARM64 commit 916b93f4e865 ("arm64: smp: Fix missing IPI
>> statistics"), commit 56afcd3dbd19 ("ARM: Allow IPIs to be handled as normal
>> interrupts") set CPU_BACKTRACE IPI "IRQ_HIDDEN" flag but not show it in
>> show_ipi_list(), which cause the interrupt kstat_irqs accounting
>> is missing in display.
>
> I don't see why this needs to be included. If this IPI fires, it means
> that the kernel has suffered a lockup and is probably not very useful.
> So the chances of being able to read out from /proc/interrupts a non-
> zero "CPU backtrace interrupts" figure is highly unlikely.
It is more of a change than a bug.
If we reset the arm32 code to before commit 56afcd3dbd19 ("ARM: Allow
IPIs to be handled as normal interrupts"), the backtrace IPI statics is
shown ok as below, but after that it is missing:
/ # cat /proc/interrupts
CPU0
24: 6 GIC-0 34 Level timer
25: 469 GIC-0 29 Level twd
26: 61 GIC-0 75 Edge virtio0
29: 8 GIC-0 44 Level kmi-pl050
30: 118 GIC-0 45 Level kmi-pl050
31: 0 GIC-0 36 Level rtc-pl031
32: 0 GIC-0 41 Level mmci-pl18x (cmd)
33: 0 GIC-0 42 Level mmci-pl18x (pio)
34: 0 GIC-0 92 Level arm-pmu
35: 0 GIC-0 93 Level arm-pmu
36: 0 GIC-0 94 Level arm-pmu
37: 0 GIC-0 95 Level arm-pmu
39: 15 GIC-0 37 Level uart-pl011
IPI0: 0 CPU wakeup interrupts
IPI1: 0 Timer broadcast interrupts
IPI2: 0 Rescheduling interrupts
IPI3: 0 Function call interrupts
IPI4: 0 CPU stop interrupts
IPI5: 0 IRQ work interrupts
IPI6: 0 completion interrupts
IPI7: 0 CPU backtrace interrupts
>
> So, I don't see much point to this change.
>
next prev parent reply other threads:[~2024-08-02 1:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-01 9:40 [PATCH] ARM: smp: Fix missing backtrace IPI statics Jinjie Ruan
2024-08-01 16:36 ` Russell King (Oracle)
2024-08-02 1:39 ` Jinjie Ruan [this message]
2024-08-02 1:44 ` Jinjie Ruan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=c55bbffe-9144-f787-eb70-8328be5cfe7c@huawei.com \
--to=ruanjinjie@huawei.com \
--cc=akpm@linux-foundation.org \
--cc=dianders@chromium.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=maz@kernel.org \
--cc=mhocko@suse.com \
--cc=vschneid@redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox