linux-kernel - [PATCH RFC] ARM: don't allow to register the early

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Date:	Thu, 18 Apr 2013 16:23:39 +0200
From:	Gregory CLEMENT <gregory.clement@...e-electrons.com>
To:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Russell King <linux@....linux.org.uk>
Cc:	Kay Sievers <kay@...y.org>,
	Ezequiel Garcia <ezequiel.garcia@...e-electrons.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Lior Amsalem <alior@...vell.com>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>
Subject: [PATCH RFC] ARM: don't allow to register the early_console twice

If on the kernel command line the parameter "earlyprintk" is written
twice, then setup_early_printk is called twice. This can happen for
example with the option CONFIG_ARM_ATAG_DTB_COMPAT_CMDLINE_EXTEND is
selected, and the "earlyprintk" is passed from the ATAG_CMDLINE and
from the dtb.

This lead to an infinite loop on the message "Booting Linux on
physical CPU 0" displayed from smp_setup_processor_id() in
arch/arm/kernel/setup.c. This behavior as been reproduced on ARMv7
architecture (Armada XP and Armada 370), and on a ARMv5 one
(AT91SAMG35 thanks to Richard Genoud), with and with CONFIG_SMP
selected.

This patch simply doesn't allow to call twice register_console() with
the early_console.

Signed-off-by: Gregory CLEMENT <gregory.clement@...e-electrons.com>
---
 arch/arm/kernel/early_printk.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/arm/kernel/early_printk.c b/arch/arm/kernel/early_printk.c
index 85aa2b2..435577a 100644
--- a/arch/arm/kernel/early_printk.c
+++ b/arch/arm/kernel/early_printk.c
@@ -50,7 +50,11 @@ asmlinkage void early_printk(const char *fmt, ...)

 static int __init setup_early_printk(char *buf)
 {
-	register_console(&early_console);
+	static int done;
+	if (!done) {
+		register_console(&early_console);
+		done = 1;
+	}
 	return 0;
 }

-- 
1.7.9.5

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