diff options
author | Ming Lei <tom.leiming@gmail.com> | 2013-03-11 13:52:12 +0100 |
---|---|---|
committer | Zhangfei Gao <zhangfei.gao@linaro.org> | 2013-10-09 17:45:49 +0800 |
commit | 036a225d4f3b751ca4acebc75b8b85c3fff89867 (patch) | |
tree | fc17ddbb5681d875c17f0e8d412b94d1c285a7a7 | |
parent | 887960cb5bb2df169ef857eda7375f1a40c7682b (diff) |
ARM: 7669/1: keep __my_cpu_offset consistent with generic onetracking-hilt-LOCKDEP-1008
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>
-rw-r--r-- | arch/arm/kernel/setup.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index 6002fe06b124..1f1eabd7b6be 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -470,6 +470,13 @@ void __init smp_setup_processor_id(void) for (i = 1; i < nr_cpu_ids; ++i) cpu_logical_map(i) = i == cpu ? 0 : i; + /* + * clear __my_cpu_offset on boot CPU to avoid hang caused by + * using percpu variable early, for example, lockdep will + * access percpu variable inside lock_release + */ + set_my_cpu_offset(0); + printk(KERN_INFO "Booting Linux on physical CPU 0x%x\n", mpidr); } |