The db->lock is a raw spinlock and so the lock hold time is supposed to be
short.  This will not be the case when printk() is being involved in some
of the critical sections.

In order to avoid the long hold time, in case some messages need to be
printed, all the debug_object_is_on_stack() and debug_print_object() calls
are now moved out of those critical sections in the following functions.

 - __debug_object_init()
 - debug_object_activate()
 - debug_object_deactivate()
 - debug_object_destroy()
 - debug_object_free()
 - debug_object_active_state()
 - __debug_check_no_obj_freed()
 - check_results()

Holding the db->lock while calling printk() may lead to deadlock if
printk() somehow requires the allocation/freeing of debug object that
happens to be in the same hash bucket or a circular lock dependency
warning from lockdep as reported in

  https://lkml.kernel.org/r/20181211091154.GL23332@shao2-debian

[   87.209665] WARNING: possible circular locking dependency detected
[   87.210547] 4.20.0-rc4-00057-gc96cf923 #1 Tainted: G        W
[   87.211449] ------------------------------------------------------
[   87.212405] getty/519 is trying to acquire lock:
[   87.213074] (____ptrval____) (&obj_hash[i].lock){-.-.}, at: debug_check_no_obj_freed+0xb4/0x302
[   87.214343]
[   87.214343] but task is already holding lock:
[   87.215174] (____ptrval____) (&port_lock_key){-.-.}, at: uart_shutdown+0x3a3/0x4e2
[   87.216260]
[   87.216260] which lock already depends on the new lock.

This patch was also found to be able to fix a boot hanging problem when
the initramfs image was switched on after a debugobjects splat from the
EFI code.

Link: http://lkml.kernel.org/r/1544738377-3848-1-git-send-email-longman@redhat.com


Signed-off-by: Waiman Long <longman@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Dmitry Safonov <dima@arista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>