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Wed, 20 May 2026 12:57:58 -0400 X-MC-Unique: mqNlTpKdPVmUgvpuygbC2A-1 X-Mimecast-MFC-AGG-ID: mqNlTpKdPVmUgvpuygbC2A_1779296277 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id F3FB91956048; Wed, 20 May 2026 16:57:56 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.248]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 349C51800465; Wed, 20 May 2026 16:57:55 +0000 (UTC) From: Waiman Long To: Thomas Gleixner , Andrew Morton , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Waiman Long Subject: [PATCH v2] debugobjects: Don't call fill_pool() in early boot non-task context of RT kernel Date: Wed, 20 May 2026 12:57:44 -0400 Message-ID: <20260520165744.921951-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" When booting a debug PREEMPT_RT kernel on an arm64 system with grace processor, the following lockdep splat was reported during early boot. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D 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+0= x74/0xa0 {HARDIRQ-ON-W} state was registered at: __lock_acquire+0x3d4/0xb70 lock_acquire.part.0+0x178/0x2e0 lock_acquire+0xa0/0x240 rt_spin_lock+0xa0/0x400 __refill_objects_node+0x8c/0x638 refill_objects+0x60/0x120 __pcs_replace_empty_main+0x11c/0x3a8 __kmalloc_noprof+0x550/0x5e0 __alloc_workqueue+0x7a4/0xb68 alloc_workqueue_noprof+0xc0/0x118 kmem_cache_init_late+0x3c/0xd8 start_kernel+0x360/0x460 __primary_switched+0x8c/0xa0 irq event stamp: 12818 hardirqs last enabled at (12817): [] __raw_spin_unlock= _irqrestore+0xb8/0xe8 hardirqs last disabled at (12818): [] el1_interrupt+0x3= 4/0xb0 softirqs last enabled at (0): [<0000000000000000>] 0x0 softirqs last disabled at (0): [<0000000000000000>] 0x0 : Call trace: show_stack+0x20/0x40 (C) dump_stack_lvl+0x7c/0x160 dump_stack+0x1c/0x48 print_usage_bug.part.0+0x248/0x270 mark_lock_irq+0x410/0x608 mark_lock+0x1ec/0x3a8 mark_usage+0x138/0x170 __lock_acquire+0x3d4/0xb70 lock_acquire.part.0+0x178/0x2e0 lock_acquire+0xa0/0x240 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.part.0+0x88/0x100 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 el1h_64_irq_handler+0x18/0x28 el1h_64_irq+0x80/0x88 The {IN-HARDIRQ-W} usage happens when debug_objects_fill_pool() calls fill_pool() in the hardirq context during early boot. It is because of the "system_state < SYSTEM_SCHEDULING" check in debug_objects_fill_pool() which allows fill_pool() to be called from any context during early boot. Calling fill_pool() from any context is problematic as deadlock can happen even though the early boot window should be pretty short. Fix that by restricting the call to only in_task() context during early boot. Fixes: 06e0ae988f6e ("debugobjects: Allow to refill the pool before SYSTEM_= SCHEDULING") Signed-off-by: Waiman Long --- lib/debugobjects.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 12e2e42e6a31..236ea5e716df 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -727,11 +727,14 @@ static void debug_objects_fill_pool(void) =20 /* * On RT enabled kernels the pool refill must happen in preemptible - * context -- for !RT kernels we rely on the fact that spinlock_t and + * context or in task context during early boot. + * + * For !RT kernels we rely on the fact that spinlock_t and * raw_spinlock_t are basically the same type and this lock-type * inversion works just fine. */ - if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible() || system_state < SYS= TEM_SCHEDULING) { + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || preemptible() || + (system_state < SYSTEM_SCHEDULING && in_task())) { /* * Annotate away the spinlock_t inside raw_spinlock_t warning * by temporarily raising the wait-type to LD_WAIT_CONFIG, matching --=20 2.54.0