linux-kernel - [PATCH 3.2 09/24] MIPS: Fix kernel lockup or crash after CPU offline/online

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Date:	Tue, 03 Mar 2015 22:11:28 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, linux-mips@...ux-mips.org,
	"Hemmo Nieminen" <hemmo.nieminen@....fi>,
	"David Daney" <david.daney@...ium.com>,
	"Ralf Baechle" <ralf@...ux-mips.org>,
	"Aaro Koskinen" <aaro.koskinen@....fi>
Subject: [PATCH 3.2 09/24] MIPS: Fix kernel lockup or crash after CPU
 offline/online

3.2.68-rc1 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>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/mips/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -105,10 +105,10 @@ asmlinkage __cpuinit void start_secondar
 	if ((read_c0_tcbind() & TCBIND_CURTC) == 0)
 #endif /* CONFIG_MIPS_MT_SMTC */
 	cpu_probe();
-	cpu_report();
 	per_cpu_trap_init();
 	mips_clockevent_init();
 	mp_ops->init_secondary();
+	cpu_report();
 
 	/*
 	 * XXX parity protection should be folded in here when it's converted

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