linux-kernel - [PATCH 0/7] proc/stat: Maintain monotonicity of "intr" and "softirq"

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Message-Id: <20210911034808.24252-1-me@ilammy.net>
Date:   Sat, 11 Sep 2021 12:48:01 +0900
From:   Alexei Lozovsky <me@...mmy.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Christoph Lameter <cl@...ux.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-fsdevel@...r.kernel.org
Subject: [PATCH 0/7] proc/stat: Maintain monotonicity of "intr" and "softirq"

Here's a patch set that makes /proc/stat report total interrupt counts
as monotonically increasing values, just like individual counters for
interrupt types and CPUs are.

This is as if the sum was a shared counter that all CPUs increment
atomically together with their individual counters, with the sum
correctly and expectedly wrapping around to zero once it reaches
UINT_MAX.

I've also added some documentation bits to codify this behavior and make
it explicit that wrap-arounds must be expected and handled if userspace
wants to maintain accurate total interrupt count for whatever reasons.

Alexei Lozovsky (7):
  genirq: Use unsigned int for irqs_sum
  powerpc/irq: arch_irq_stat_cpu() returns unsigned int
  x86/irq: arch_irq_stat_cpu() returns unsigned int
  x86/irq: arch_irq_stat() returns unsigned int
  proc/stat: Use unsigned int for "intr" sum
  proc/stat: Use unsigned int for "softirq" sum
  docs: proc.rst: stat: Note the interrupt counter wrap-around

 Documentation/filesystems/proc.rst | 7 +++++++
 arch/powerpc/include/asm/hardirq.h | 2 +-
 arch/powerpc/kernel/irq.c          | 4 ++--
 arch/x86/include/asm/hardirq.h     | 4 ++--
 arch/x86/kernel/irq.c              | 8 ++++----
 fs/proc/stat.c                     | 8 ++++----
 include/linux/kernel_stat.h        | 2 +-
 7 files changed, 21 insertions(+), 14 deletions(-)

-- 
2.25.1