linux-kernel - Re: [PATCH v5 2/4] printk/nmi: warn when some message has been lost in NMI context

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Message-ID: <20160427093438.GK19428@n2100.arm.linux.org.uk>
Date:	Wed, 27 Apr 2016 10:34:38 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Daniel Thompson <daniel.thompson@...aro.org>,
	Jiri Kosina <jkosina@...e.com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Chris Metcalf <cmetcalf@...hip.com>,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org,
	adi-buildroot-devel@...ts.sourceforge.net,
	linux-cris-kernel@...s.com, linux-mips@...ux-mips.org,
	linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org,
	Jan Kara <jack@...e.cz>, Ralf Baechle <ralf@...ux-mips.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH v5 2/4] printk/nmi: warn when some message has been lost
 in NMI context

On Thu, Apr 21, 2016 at 01:48:43PM +0200, Petr Mladek wrote:
> @@ -64,8 +65,10 @@ static int vprintk_nmi(const char *fmt, va_list args)
>  again:
>  	len = atomic_read(&s->len);
>  
> -	if (len >= sizeof(s->buffer))
> +	if (len >= sizeof(s->buffer)) {
> +		atomic_inc(&nmi_message_lost);

This should be fine - I think its reasonable to expect that no one is
using a spinlock implementation for their atomic ops for this...

-- 
RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/
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