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authorMing Lei <tom.leiming@gmail.com>2013-03-11 13:52:12 +0100
committerRussell King <rmk+kernel@arm.linux.org.uk>2013-05-15 19:35:52 +0100
commit9394c1c65e61eb6f4c1c99f342b49e451ec337b6 (patch)
tree6489788b82160a0d4361f15fa7647a3cc9fce955 /arch
parentf722406faae2d073cc1d01063d1123c35425939e (diff)
downloadlinux-9394c1c65e61eb6f4c1c99f342b49e451ec337b6.tar.bz2
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>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/kernel/setup.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 1522c7ae31b0..dd1c6aacbaf9 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -456,6 +456,13 @@ 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);
}