linux-kernel - [PATCH 2/2] MIPS: fix kernel lockup or crash after CPU offline/online

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Date:	Thu, 15 Jan 2015 20:49:27 +0200
From:	Aaro Koskinen <aaro.koskinen@....fi>
To:	Ralf Baechle <ralf@...ux-mips.org>,
	David Daney <david.daney@...ium.com>,
	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Cc:	Hemmo Nieminen <hemmo.nieminen@....fi>, stable@...r.kernel.org,
	Aaro Koskinen <aaro.koskinen@....fi>
Subject: [PATCH 2/2] MIPS: fix kernel lockup or crash after CPU offline/online

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

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: stable@...r.kernel.org
---
 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 c94c4e9..1c0d8c5 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -123,10 +123,10 @@ 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
-- 
2.2.0

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