ARM: 7669/1: keep __my_cpu_offset consistent with generic one
authorMing Lei <tom.leiming@gmail.com>
Mon, 11 Mar 2013 12:52:12 +0000 (13:52 +0100)
committerRussell King <rmk+kernel@arm.linux.org.uk>
Wed, 15 May 2013 18:35:52 +0000 (19:35 +0100)
commit9394c1c65e61eb6f4c1c99f342b49e451ec337b6
tree6489788b82160a0d4361f15fa7647a3cc9fce955
parentf722406faae2d073cc1d01063d1123c35425939e
ARM: 7669/1: keep __my_cpu_offset consistent with generic one

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>
arch/arm/kernel/setup.c