[PATCH 3.13.y-ckt 68/80] MIPS: Fix kernel lockup or crash after CPU offline/online

Kamal Mostafa kamal at canonical.com
Thu Mar 19 22:35:56 UTC 2015

3.13.11-ckt17 -stable review patch.  If anyone has any objections, please let me know.


From: Hemmo Nieminen <hemmo.nieminen at iki.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 at iki.fi>
Signed-off-by: Aaro Koskinen <aaro.koskinen at iki.fi>
Cc: David Daney <david.daney at cavium.com>
Cc: linux-mips at linux-mips.org
Cc: linux-kernel at vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8953/
Signed-off-by: Ralf Baechle <ralf at linux-mips.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.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 0a022ee..18ed112 100644
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -109,10 +109,10 @@ asmlinkage void start_secondary(void)
 #endif /* CONFIG_MIPS_MT_SMTC */
-	cpu_report();
+	cpu_report();
 	 * XXX parity protection should be folded in here when it's converted

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