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SubjectRe: INFO: trying to register non-static key in try_to_wake_up

On 3/31/20 12:18 PM, Dmitry Vyukov wrote:
> On Tue, Mar 31, 2020 at 11:57 AM Peter Zijlstra <> wrote:
>> On Mon, Mar 30, 2020 at 10:01:12PM -0700, syzbot wrote:
>>> Hello,
>>> syzbot found the following crash on:
>>> HEAD commit: 9420e8ad Merge tag 'for-linus' of git://
>>> git tree: upstream
>>> console output:
>>> kernel config:
>>> dashboard link:
>>> compiler: gcc (GCC) 9.0.0 20181231 (experimental)
>>> Unfortunately, I don't have any reproducer for this crash yet.
>>> IMPORTANT: if you fix the bug, please add the following tag to the commit:
>>> Reported-by:
>>> INFO: trying to register non-static key.
>>> the code is fine but needs lockdep annotation.
>>> turning off the locking correctness validator.
>>> CPU: 1 PID: 1014 Comm: syz-executor.0 Not tainted 5.6.0-rc7-syzkaller #0
>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>>> Call Trace:
>>> <IRQ>
>>> __dump_stack lib/dump_stack.c:77 [inline]
>>> dump_stack+0x188/0x20d lib/dump_stack.c:118
>>> assign_lock_key kernel/locking/lockdep.c:880 [inline]
>>> register_lock_class+0x14c4/0x1540 kernel/locking/lockdep.c:1189
>>> __lock_acquire+0xfc/0x3ca0 kernel/locking/lockdep.c:3836
>>> lock_acquire+0x197/0x420 kernel/locking/lockdep.c:4484
>>> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
>>> _raw_spin_lock_irqsave+0x8c/0xbf kernel/locking/spinlock.c:159
>>> try_to_wake_up+0x9f/0x17c0 kernel/sched/core.c:2547
>> That's p->pi_lock, which gets initialized in rt_mutex_init_task() in
>> copy_process(). This should be impossible. Very odd.
> The stack mentions fbdev, which is a red flag at the moment. There are
> a dozen of bad bugs in fbdev and around. Just few days ago Andy
> pointed to another "impossible" crash "general protection fault in
> do_syscall_64" which is related to dri:
> There are probably more random manifestations of these bugs already,
> and I guess we will be getting more.
> +fbdev maintainers

Thank you for the report.

fbdev is in the maintenance mode and no new features or drivers are
being added so syzbot reports are not for a new bugs (regressions) and
are not a priority (at least to me).

I have only resources to review/merge pending fbdev patches from time
to time so any help in fixing these syzbot reports is welcomed (there
have been a few fbdev related syzbot reports recently).

Also please note that fbdev is maintained through drm-misc tree so
patches can also be handled by other drm-misc maintainers in case I'm
not available / busy with other things.

Best regards,
Bartlomiej Zolnierkiewicz
Samsung R&D Institute Poland
Samsung Electronics

>>> wake_up_worker kernel/workqueue.c:836 [inline]
>>> insert_work+0x2ad/0x3a0 kernel/workqueue.c:1337
>>> __queue_work+0x50d/0x1280 kernel/workqueue.c:1488
>>> call_timer_fn+0x195/0x760 kernel/time/timer.c:1404
>>> expire_timers kernel/time/timer.c:1444 [inline]
>>> __run_timers kernel/time/timer.c:1773 [inline]
>>> __run_timers kernel/time/timer.c:1740 [inline]
>>> run_timer_softirq+0x412/0x1600 kernel/time/timer.c:1786
>>> __do_softirq+0x26c/0x99d kernel/softirq.c:292
>>> invoke_softirq kernel/softirq.c:373 [inline]
>>> irq_exit+0x192/0x1d0 kernel/softirq.c:413
>>> exiting_irq arch/x86/include/asm/apic.h:546 [inline]
>>> smp_apic_timer_interrupt+0x19e/0x600 arch/x86/kernel/apic/apic.c:1146
>>> apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
>>> </IRQ>

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