ARM: 7669/1: keep __my_cpu_offset consistent with generic one

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Commit 14318efb(ARM: 7587/1: implement optimized percpu variable access)
introduces arm's __my_cpu_offset to optimize percpu vaiable access,
which really works well on hackbench, but will cause __my_cpu_offset
to return garbage value before it is initialized in cpu_init() called
by setup_arch, so accessing percpu variable before setup_arch may cause
kernel hang. But generic __my_cpu_offset always returns zero before
percpu area is brought up, and won't hang kernel.

So the patch tries to clear __my_cpu_offset on boot CPU early
to avoid boot hang.

At least now percpu variable is accessed by lockdep before
setup_arch(), and enabling CONFIG_LOCK_STAT or CONFIG_DEBUG_LOCKDEP
can trigger kernel hang.

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

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Ming Lei 2013-03-11 13:52:12 +01:00 • committed by Russell King

parent f722406faa

commit 9394c1c65e

1 changed files with 7 additions and 0 deletions

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arch/arm/kernel/setup.c

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