linux-kernel - [PATCH 3.16.y-ckt 11/58] MIPS: Fix kernel lockup or crash after CPU offline/online

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Message-Id: <1424353948-31863-12-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 19 Feb 2015 13:51:41 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Hemmo Nieminen <hemmo.nieminen@....fi>,
	Aaro Koskinen <aaro.koskinen@....fi>,
	David Daney <david.daney@...ium.com>,
	linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 11/58] MIPS: Fix kernel lockup or crash after CPU offline/online

3.16.7-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hemmo Nieminen <hemmo.nieminen@....fi>

commit c7754e75100ed5e3068ac5085747f2bfc386c8d6 upstream.

As printk() invocation can cause e.g. a TLB miss, printk() cannot be
called before the exception handlers have been properly initialized.
This can happen e.g. when netconsole has been loaded as a kernel module
and the TLB table has been cleared when a CPU was offline.

Call cpu_report() in start_secondary() only after the exception handlers
have been initialized to fix this.

Without the patch the kernel will randomly either lockup or crash
after a CPU is onlined and the console driver is a module.

Signed-off-by: Hemmo Nieminen <hemmo.nieminen@....fi>
Signed-off-by: Aaro Koskinen <aaro.koskinen@....fi>
Cc: David Daney <david.daney@...ium.com>
Cc: linux-mips@...ux-mips.org
Cc: linux-kernel@...r.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8953/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 arch/mips/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 9bad52ede903..9bc3561b6901 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -101,10 +101,10 @@ asmlinkage void start_secondary(void)
 	unsigned int cpu;
 
 	cpu_probe();
-	cpu_report();
 	per_cpu_trap_init(false);
 	mips_clockevent_init();
 	mp_ops->init_secondary();
+	cpu_report();
 
 	/*
 	 * XXX parity protection should be folded in here when it's converted
-- 
2.1.4

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