[PATCH -next] lockdep: skip debugobjects for lock_classes[] init

[Qian Cai]

The linux-next commit a0b0fd53e1e6 ("locking/lockdep: Free lock classes
that are no longer in use") let init_data_structures_once() call
init_rcu_head(). As the result, smp_setup_processor_id() calls
debug_object_init() before debug_objects_early_init() triggering errors
below on arm64 and ppc64le. Since debug_objects_early_init() depends on
smp_setup_processor_id(), so it is not straightforward to move the
former earlier in start_kernel(). Hence, just skip all debugobjects
creations in init_data_structures_once() as a good trade-off by losing
track of some RCU list heads debugging.

BUG: spinlock bad magic on CPU#0, swapper/0
 lock: obj_hash+0xc3048/0x100000, .magic: 00000000, .owner: <none>/-1,
.owner_cpu: 0
CPU: 0 PID: 0 Comm: swapper Not tainted 5.0.0-rc8-next-20190301+ #1
Call trace:
 dump_backtrace+0x0/0x450
 show_stack+0x20/0x2c
 dump_stack+0xe0/0x16c
 spin_bug+0x200/0x224
 do_raw_spin_lock+0x1bc/0x23c
 _raw_spin_lock_irqsave+0xac/0xd0
 __debug_object_init+0xf0/0x19dc
 debug_object_init+0x54/0x6c
 init_rcu_head+0x24/0x30
 init_data_structures_once+0xb0/0x41c
 register_lock_class+0x70c/0x1454
 __lock_acquire+0xc4/0x235c
 lock_acquire+0x508/0x668
 _raw_spin_lock+0x88/0xac
 vprintk_emit+0x33c/0x53c
 vprintk_default+0x54/0x7c
 vprintk_func+0x320/0x40c
 printk+0x64/0x8c
 smp_setup_processor_id+0x6c/0x84
 start_kernel+0x38/0x8f8
ODEBUG: Out of memory. ODEBUG disabled

Signed-off-by: Qian Cai <cai@xxxxxx>
---
 kernel/locking/lockdep.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 21cb81fe6359..1309a6fe88ee 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -988,7 +988,6 @@ static void init_data_structures_once(void)
 
 	initialization_happened = true;
 
-	init_rcu_head(&delayed_free.rcu_head);
 	INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
 	INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
 
-- 
2.17.2 (Apple Git-113)