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Message-ID: <CAMuHMdXVgr58YjoePGrRbMyMncQ27f85prL7G5SpeHeNxoYrXQ@mail.gmail.com>
Date: Fri, 11 Dec 2015 12:10:02 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Petr Mladek <pmladek@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Russell King <rmk+kernel@....linux.org.uk>,
Daniel Thompson <daniel.thompson@...aro.org>,
Jiri Kosina <jkosina@...e.com>, Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"the arch/x86 maintainers" <x86@...nel.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"adi-buildroot-devel@...ts.sourceforge.net"
<adi-buildroot-devel@...ts.sourceforge.net>,
Cris <linux-cris-kernel@...s.com>,
Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
linux-s390 <linux-s390@...r.kernel.org>,
Linux-sh list <linux-sh@...r.kernel.org>,
sparclinux <sparclinux@...r.kernel.org>
Subject: Re: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and
make it configurable
On Wed, Dec 9, 2015 at 2:21 PM, Petr Mladek <pmladek@...e.com> wrote:
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -866,6 +866,28 @@ config LOG_CPU_MAX_BUF_SHIFT
> 13 => 8 KB for each CPU
> 12 => 4 KB for each CPU
>
> +config NMI_LOG_BUF_SHIFT
> + int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)"
> + range 10 21
> + default 13
> + depends on PRINTK && HAVE_NMI
Symbol NMI_LOG_BUF_SHIFT does not exist if its dependencies are not met.
> + help
> + Select the size of a per-CPU buffer where NMI messages are temporary
> + stored. They are copied to the main log buffer in a safe context
> + to avoid a deadlock. The value defines the size as a power of 2.
> +
> + NMI messages are rare and limited. The largest one is when
> + a backtrace is printed. It usually fits into 4KB. Select
> + 8KB if you want to be on the safe side.
> +
> + Examples:
> + 17 => 128 KB for each CPU
> + 16 => 64 KB for each CPU
> + 15 => 32 KB for each CPU
> + 14 => 16 KB for each CPU
> + 13 => 8 KB for each CPU
> + 12 => 4 KB for each CPU
> +
> #
> # Architectures with an unreliable sched_clock() should select this:
> #
> diff --git a/kernel/printk/nmi.c b/kernel/printk/nmi.c
> index 5465230b75ec..78c07d441b4e 100644
> --- a/kernel/printk/nmi.c
> +++ b/kernel/printk/nmi.c
> @@ -41,7 +41,8 @@ DEFINE_PER_CPU(printk_func_t, printk_func) = vprintk_default;
> static int printk_nmi_irq_ready;
> atomic_t nmi_message_lost;
>
> -#define NMI_LOG_BUF_LEN (4096 - sizeof(atomic_t) - sizeof(struct irq_work))
> +#define NMI_LOG_BUF_LEN ((1 << CONFIG_NMI_LOG_BUF_SHIFT) - \
> + sizeof(atomic_t) - sizeof(struct irq_work))
kernel/printk/nmi.c:50:24: error: 'CONFIG_NMI_LOG_BUF_SHIFT'
undeclared here (not in a function)
E.g. efm32_defconfig
http://kisskb.ellerman.id.au/kisskb/buildresult/12565754/
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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