linux-kernel - Re: [PATCH v3] genirq: Machine-parsable version of /proc/interrupts

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Date:   Thu, 8 Sep 2016 15:00:50 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Craig Gallek <kraigatgoog@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     David Decotigny <decot@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] genirq: Machine-parsable version of /proc/interrupts

On 09/08/16 13:25, Craig Gallek wrote:
> From: Craig Gallek <kraig@...gle.com>
> 
> Add struct kobject to struct irq_desc to allow for easy export
> to sysfs.  This allows for much simpler userspace-parsing of
> the information contained in struct irq_desc.
> 
> Note that sysfs is not available at the time of early irq initialization.
> These interrupts are accounted for using a postcore_initcall callback.
> 
> Examples:
>   /sys/kernel/irq/18/actions:	i801_smbus,ehci_hcd:usb1,uhci_hcd:usb7
>   /sys/kernel/irq/18/chip_name:	IR-IO-APIC
>   /sys/kernel/irq/18/hwirq:		18
>   /sys/kernel/irq/18/name:		fasteoi
>   /sys/kernel/irq/18/per_cpu_count:	0,0
>   /sys/kernel/irq/18/type:		level
> 
>   /sys/kernel/irq/25/actions:	ahci0
>   /sys/kernel/irq/25/chip_name:	IR-PCI-MSI
>   /sys/kernel/irq/25/hwirq:		512000
>   /sys/kernel/irq/25/name:		edge
>   /sys/kernel/irq/25/per_cpu_count:	29036,0
>   /sys/kernel/irq/25/type:		edge

Thanks for the update.

One concern:

This per_cpu_count is for online CPUs only.
How does this help when the online CPUs change?

E.g., above could be for CPUs 1 and 5.
The next time that it is read it could be for CPUs 0 and 3.
Seems that it could be confusing even for software reading it.


-- 
~Randy