linux-kernel - Re: [RFC][PATCH] bug: Add _ONCE logic to report

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Date:   Sat, 25 Feb 2017 10:18:23 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        torvalds@...ux-foundation.org, arjan@...ux.intel.com, bp@...en8.de,
        jpoimboe@...hat.com, richard.weinberger@...il.com
Subject: Re: [RFC][PATCH] bug: Add _ONCE logic to report_bug()


* Peter Zijlstra <peterz@...radead.org> wrote:

> 
> Josh suggested moving the _ONCE logic inside the trap handler, using a
> bit in the bug_entry::flags field, avoiding the need for the extra
> variable.

This looks interesting, as the _ONCE() methods of warning are far more 
user-friendly than WARN() spam.

> Sadly this only works for WARN_ON_ONCE(), since the others have
> printk() statements prior to triggering the trap.

Which one is problematic to convert, WARN_ONCE()?

> Still, this saves some text and data:
> 
>   text            data     bss    dec              hex    filename
>   10469505        4443448  843776 15756729         f06db9 defconfig-build/vmlinux-ud0
>   10452803        4442616  843776 15739195         f0293b defconfig-build/vmlinux-ud0-once
> 
> (Only compile tested on x86_64 so far.)

That looks pretty sweet, as various almost never triggered _ONCE() checks tend to 
disturb the generated machine code quite a bit ...

Thanks,

	Ingo