Re: [PATCH v4] debugobjects: Don't call fill_pool() in early boot hardirq context

[Waiman Long]

On 6/5/26 2:31 AM, Sebastian Andrzej Siewior wrote:
> On 2026-06-03 15:52:50 [-0400], Waiman Long wrote:
> > When booting a debug PREEMPT_RT kernel on an arm64 system with grace
> > processor, the following lockdep warning was reported during early boot.
> >
> >    ================================
> >    WARNING: inconsistent lock state
> >    7.1.0-rc4-test+ #1 Not tainted
> >    --------------------------------
> >    inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
> >    swapper/0/0 [HC1[1]:SC0[0]:HE0:SE1] takes:
> >    ffff0000803346a0 (&n->list_lock){?.+.}-{3:3}, at: get_from_partial_node+0x74/0xa0
> >      :
> >    Call trace:
> >      :
> >     rt_spin_lock+0xa0/0x400
> >     get_from_partial_node+0x74/0xa0
> >     ___slab_alloc+0x94/0x4f8
> >     kmem_cache_alloc_noprof+0x2d4/0x598
> >     kmem_alloc_batch+0x54/0x170
> >     fill_pool+0x12c/0x438
> >     debug_objects_fill_pool+0x58/0x60
> >     debug_object_activate+0xfc/0x3d0
> >     add_timer_on+0x250/0x3a0
> >     add_interrupt_randomness+0x2d4/0x340
> >     handle_percpu_devid_irq+0x2e0/0x4e0
> >     handle_irq_desc+0xc0/0x120
> >     generic_handle_domain_irq+0x20/0x40
> >     __gic_handle_irq_from_irqson.isra.0+0x3c4/0x708
> >     gic_handle_irq+0x7c/0xe0
> >     call_on_irq_stack+0x30/0x48
> >     do_interrupt_handler+0x134/0x158
> >     el1_interrupt+0x48/0xb0
> >      :
> I would strip that backtrace since it is obvious from the description
> below.

Sure. I can do that.

> > During early boot, interrupts are getting enabled before the scheduler
> > is enabled. In this window (before SYSTEM_SCHEDULING is set) interrupts
> > can fire and attempt to fill the pool from within the hardirq. This can
> > lead to a deadlock the interrupt occurred while in the memory allocator.
> >
> > Add a new can_fill_pool() helper and reorder the exception rule and
> > forbid this scenario by excluding allocations from hardirq.
> >
> > Fixes: 06e0ae988f6e ("debugobjects: Allow to refill the pool before SYSTEM_SCHEDULING")
> > Co-developed-by: Waiman Long <longman@xxxxxxxxxx>
> > Co-developed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> > Co-developed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Thanks,
Longman
> Sebastian