Add the missing lockdep annotation to avoid this warning:
INFO: trying to register non-static key.
The code is fine but needs lockdep annotation, or maybe
you didn't initialize this object before use?
turning off the locking correctness validator.
CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5+ #681
Hardware name: 9000/785/C3700
Backtrace:
[<000000004030bcd0>] show_stack+0x74/0xb0
[<0000000041469c7c>] dump_stack_lvl+0x104/0x180
[<0000000041469d2c>] dump_stack+0x34/0x48
[<000000004040e5b4>] register_lock_class+0xd24/0xd30
[<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
[<000000004040cd60>] lock_acquire+0x130/0x298
[<000000004146df54>] _raw_spin_lock_irq+0x60/0xb8
[<0000000041472044>] wait_for_completion+0xa0/0x2d0
[<000000004146b544>] kernel_init+0x48/0x3a8
[<0000000040302020>] ret_from_kernel_thread+0x20/0x28
Signed-off-by: Helge Deller <[email protected]>
diff --git a/init/main.c b/init/main.c
index ad920fac325c..11870ca752de 100644
--- a/init/main.c
+++ b/init/main.c
@@ -682,6 +682,8 @@ noinline void __ref __noreturn rest_init(void)
struct task_struct *tsk;
int pid;
+ init_completion(&kthreadd_done);
+
rcu_scheduler_starting();
/*
* We need to spawn init first so that it obtains pid 1, however
On Fri, 11 Aug 2023 18:04:22 +0200 Helge Deller <[email protected]> wrote:
> Add the missing lockdep annotation to avoid this warning:
>
> INFO: trying to register non-static key.
> The code is fine but needs lockdep annotation, or maybe
> you didn't initialize this object before use?
> turning off the locking correctness validator.
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5+ #681
> Hardware name: 9000/785/C3700
> Backtrace:
> [<000000004030bcd0>] show_stack+0x74/0xb0
> [<0000000041469c7c>] dump_stack_lvl+0x104/0x180
> [<0000000041469d2c>] dump_stack+0x34/0x48
> [<000000004040e5b4>] register_lock_class+0xd24/0xd30
> [<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
> [<000000004040cd60>] lock_acquire+0x130/0x298
> [<000000004146df54>] _raw_spin_lock_irq+0x60/0xb8
> [<0000000041472044>] wait_for_completion+0xa0/0x2d0
> [<000000004146b544>] kernel_init+0x48/0x3a8
> [<0000000040302020>] ret_from_kernel_thread+0x20/0x28
>
> ...
>
> --- a/init/main.c
> +++ b/init/main.c
> @@ -682,6 +682,8 @@ noinline void __ref __noreturn rest_init(void)
> struct task_struct *tsk;
> int pid;
>
> + init_completion(&kthreadd_done);
> +
> rcu_scheduler_starting();
> /*
> * We need to spawn init first so that it obtains pid 1, however
This is pretty old code, as is the page_alloc_init_late() change. Do
we know why this warning has just turned up lately?
I'll add cc:stable to these, but might take that away again if we can
answer the above.
btw, please don't forget the "^---$" between changelog and patch.
On 8/11/23 18:43, Andrew Morton wrote:
> On Fri, 11 Aug 2023 18:04:22 +0200 Helge Deller <[email protected]> wrote:
>
>> Add the missing lockdep annotation to avoid this warning:
>>
>> INFO: trying to register non-static key.
>> The code is fine but needs lockdep annotation, or maybe
>> you didn't initialize this object before use?
>> turning off the locking correctness validator.
>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5+ #681
>> Hardware name: 9000/785/C3700
>> Backtrace:
>> [<000000004030bcd0>] show_stack+0x74/0xb0
>> [<0000000041469c7c>] dump_stack_lvl+0x104/0x180
>> [<0000000041469d2c>] dump_stack+0x34/0x48
>> [<000000004040e5b4>] register_lock_class+0xd24/0xd30
>> [<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
>> [<000000004040cd60>] lock_acquire+0x130/0x298
>> [<000000004146df54>] _raw_spin_lock_irq+0x60/0xb8
>> [<0000000041472044>] wait_for_completion+0xa0/0x2d0
>> [<000000004146b544>] kernel_init+0x48/0x3a8
>> [<0000000040302020>] ret_from_kernel_thread+0x20/0x28
>>
>> ...
>>
>> --- a/init/main.c
>> +++ b/init/main.c
>> @@ -682,6 +682,8 @@ noinline void __ref __noreturn rest_init(void)
>> struct task_struct *tsk;
>> int pid;
>>
>> + init_completion(&kthreadd_done);
>> +
>> rcu_scheduler_starting();
>> /*
>> * We need to spawn init first so that it obtains pid 1, however
>
> This is pretty old code, as is the page_alloc_init_late() change. Do
> we know why this warning has just turned up lately?
I haven't debugged in depth yet, but here is what I believe is the reason
why I do see those lockdep warnings and others not.
I'm building & testing on the parisc platform.
Just recently I added lockdep support to parisc for kernel 6.4 and backported
it to v6.0+. Since then I've seen the warnings.
And I think the main reason why I see those warnings on parisc and
others on other platforms don't, is that parisc is the only architecture
where __ARCH_SPIN_LOCK_UNLOCKED_VAL is NOT zero (0x1a46 actually).
The reason is that parisc offers only one assembler instruction which
operates atomicly on memory, and which we use to lock spinlocks:
ldcw ("load and clear word").
So, a "zero" spinlock word means the lock is locked, while non-zero means
it's unlocked.
For other platforms it's the other way around.
So, for a structure in e.g. __initdata[] which is pre-initialized by the compiler,
the spinlocks are locked by default (lockword = 0) on parisc, if they haven't
been initialized correctly, and thus the kernel will complain at runtime.
Now, maybe lockdep doesn't use spinlocks per se. I have't checked in depth yet,
but I'm sure it's somehow related to the odd __ARCH_SPIN_LOCK_UNLOCKED_VAL value
of parisc.
I wonder if the same bug appears if you use a non-zero __ARCH_SPIN_LOCK_UNLOCKED_VAL
on other platforms too (if it's possible).
> I'll add cc:stable to these, but might take that away again if we can
> answer the above.
Thanks for adding the patches.
I did sent two other patches as well: for watchdog and devtmpfs..
> btw, please don't forget the "^---$" between changelog and patch.
Ok.
Helge
Hi Andrew,
On 8/11/23 19:44, Helge Deller wrote:
> On 8/11/23 18:43, Andrew Morton wrote:
>> On Fri, 11 Aug 2023 18:04:22 +0200 Helge Deller <[email protected]> wrote:
>>
>>> Add the missing lockdep annotation to avoid this warning:
>>>
>>> INFO: trying to register non-static key.
>>> The code is fine but needs lockdep annotation, or maybe
>>> you didn't initialize this object before use?
>>> turning off the locking correctness validator.
>>> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.5.0-rc5+ #681
>>> Hardware name: 9000/785/C3700
>>> Backtrace:
>>> [<000000004030bcd0>] show_stack+0x74/0xb0
>>> [<0000000041469c7c>] dump_stack_lvl+0x104/0x180
>>> [<0000000041469d2c>] dump_stack+0x34/0x48
>>> [<000000004040e5b4>] register_lock_class+0xd24/0xd30
>>> [<000000004040c21c>] __lock_acquire.isra.0+0xb4/0xac8
>>> [<000000004040cd60>] lock_acquire+0x130/0x298
>>> [<000000004146df54>] _raw_spin_lock_irq+0x60/0xb8
>>> [<0000000041472044>] wait_for_completion+0xa0/0x2d0
>>> [<000000004146b544>] kernel_init+0x48/0x3a8
>>> [<0000000040302020>] ret_from_kernel_thread+0x20/0x28
>>>
>>> ...
>>>
>>> --- a/init/main.c
>>> +++ b/init/main.c
>>> @@ -682,6 +682,8 @@ noinline void __ref __noreturn rest_init(void)
>>> struct task_struct *tsk;
>>> int pid;
>>>
>>> + init_completion(&kthreadd_done);
>>> +
>>> rcu_scheduler_starting();
>>> /*
>>> * We need to spawn init first so that it obtains pid 1, however
>>
>> This is pretty old code, as is the page_alloc_init_late() change. Do
>> we know why this warning has just turned up lately?
[dropped Helge's assumptions that it's related to parisc's unusual
__ARCH_SPIN_LOCK_UNLOCKED_VAL value. It turned out to be wrong.
Now I was able to trace down why I see those lockdep warnings on parisc.
The short answer is:
On parisc the _initdata section lies outside of the usual kernel
_stext ... _end range. Lockdep calls static_obj() which currently assumes
that __initdata is inside that range and thus returns "false".
That's why lockdep then reports
INFO: trying to register non-static key.
which is wrong.
Please drop those 3 lockdep patches from your mm-queue:
mm-add-lockdep-annotation-to-pgdat_init_all_done_comp-completer.patch
init-add-lockdep-annotation-to-kthreadd_done-completer.patch
watchdog-fix-lockdep-warning.patch
I'll send one single patch which fixes static_obj() instead.
Thanks,
Helge