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Wed, 20 May 2026 16:15:30 -0400 X-MC-Unique: G2c_6gfkOr25UzK0U1LPUw-1 X-Mimecast-MFC-AGG-ID: G2c_6gfkOr25UzK0U1LPUw_1779308129 Received: from mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.95]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7B9AE19560AA; Wed, 20 May 2026 20:15:28 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.22.64.248]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 9285D1681; Wed, 20 May 2026 20:15:26 +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-tip v3] debugobjects: Don't call fill_pool() in early boot non-task context Date: Wed, 20 May 2026 16:15:09 -0400 Message-ID: <20260520201509.931905-1-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 3.6 on 10.30.177.95 Content-Type: text/plain; charset="utf-8" When booting a debug PREEMPT_RT kernel on an arm64 system with grace processor, the following lockdep warning 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 : 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 : The {IN-HARDIRQ-W} usage happens when debug_objects_fill_pool() calls fill_pool() in the hardirq context during early boot. It is caused by the "system_state < SYSTEM_SCHEDULING" check in debug_objects_fill_pool() which allows fill_pool() to be called from any context during early boot before scheduling is enabled. 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 fill_pool() 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 | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) [v3] Rebased on top of tip/urgent/core & trim call trace. diff --git a/lib/debugobjects.c b/lib/debugobjects.c index 772ddabcbe7d..76bfc2571591 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -736,11 +736,15 @@ static void debug_objects_fill_pool(void) =20 /* * On RT enabled kernels the pool refill must happen in preemptible - * context and not enqueued on an rt_mutex -- 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. + * context and not enqueued on an rt_mutex or in task context during + * early boot before scheduling starts. + * + * 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) || system_state < SYSTEM_SCHEDULING || + if (!IS_ENABLED(CONFIG_PREEMPT_RT) || + (system_state < SYSTEM_SCHEDULING && in_task()) || (preemptible() && !debug_objects_is_pi_blocked_on())) { /* * Annotate away the spinlock_t inside raw_spinlock_t warning --=20 2.54.0