Re: [PATCH 0/2] onlining cpus can break lockdep

[Glauber Costa <gcosta@redhat.com>]

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Ingo Molnar wrote:
> * Glauber Costa <gcosta@redhat.com> wrote:
> 
>> Hi,
>>
>> While testing with hotplugging cpus today, I've came across a stack 
>> trace generated by lockdep. The reason for that is that do_boot_cpu() 
>> in smpboot_64.c ends up initializing a struct work_struct variable in 
>> the stack.
> 
> hm, could you post that trace?

Sure. To make it clearer where the problem is, I also added the attached 
patch to my testing.

Trace is: (note the call to do_fork_idle)

INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
key: ffff81003bdf9d18, name: c_idle.work
Pid: 11, comm: events/1 Not tainted 2.6.25-rc2 #129

Call Trace:
  [<ffffffff8104f757>] static_obj+0x5d/0x74
  [<ffffffff81052218>] __lock_acquire+0x8b5/0xc3e
  [<ffffffff81042e7f>] run_workqueue+0x84/0x1df
  [<ffffffff810529ef>] lock_acquire+0x91/0xbc
  [<ffffffff81042e90>] run_workqueue+0x95/0x1df
  [<ffffffff81291746>] do_fork_idle+0x0/0x20
  [<ffffffff81042ed4>] run_workqueue+0xd9/0x1df
  [<ffffffff81043951>] worker_thread+0x90/0x9b
  [<ffffffff8104632a>] autoremove_wake_function+0x0/0x2e
  [<ffffffff810438c1>] worker_thread+0x0/0x9b
  [<ffffffff8104620c>] kthread+0x47/0x73
  [<ffffffff812986c9>] trace_hardirqs_on_thunk+0x35/0x3a
  [<ffffffff8100d0e8>] child_rip+0xa/0x12
  [<ffffffff8100c67c>] restore_args+0x0/0x34
  [<ffffffff81046095>] kthreadd+0x14a/0x16f
  [<ffffffff81046095>] kthreadd+0x14a/0x16f
  [<ffffffff810461c5>] kthread+0x0/0x73
  [<ffffffff8100d0de>] child_rip+0x0/0x12

[-- Attachment #2: lockdep.patch --]
[-- Type: text/x-patch, Size: 461 bytes --]

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 3574379..572df7d 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -730,6 +730,7 @@ register_lock_class(struct lockdep_map *
 		printk("INFO: trying to register non-static key.\n");
 		printk("the code is fine but needs lockdep annotation.\n");
 		printk("turning off the locking correctness validator.\n");
+		printk("key: %p, name: %s\n", lock->key, lock->name);
 		dump_stack();
 
 		return NULL;