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Fri, 05 Jun 2026 13:18:11 -0400 X-MC-Unique: RhCywwyQNYyMB-R_4nnpRA-1 X-Mimecast-MFC-AGG-ID: RhCywwyQNYyMB-R_4nnpRA_1780679890 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-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id CE4BF180034B; Fri, 5 Jun 2026 17:18:09 +0000 (UTC) Received: from [10.22.88.138] (unknown [10.22.88.138]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 1C38227A; Fri, 5 Jun 2026 17:18:07 +0000 (UTC) Message-ID: <70e3c4e4-7a20-413c-be2b-75f1b18edc54@redhat.com> Date: Fri, 5 Jun 2026 13:18:07 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4] debugobjects: Don't call fill_pool() in early boot hardirq context To: Sebastian Andrzej Siewior Cc: Thomas Gleixner , Andrew Morton , Clark Williams , Steven Rostedt , linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev References: <20260603195250.362595-1-longman@redhat.com> <20260605063115.ff4VR-pH@linutronix.de> Content-Language: en-US From: Waiman Long In-Reply-To: <20260605063115.ff4VR-pH@linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.6 on 10.30.177.95 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 >> Co-developed-by: Sebastian Andrzej Siewior >> Co-developed-by: Thomas Gleixner >> Signed-off-by: Waiman Long > Reviewed-by: Sebastian Andrzej Siewior Thanks, Longman > > Sebastian >