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Wed, 20 May 2026 12:57:11 -0400 X-MC-Unique: s_ju312PNjaUTH3jEBgHlw-1 X-Mimecast-MFC-AGG-ID: s_ju312PNjaUTH3jEBgHlw_1779296230 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id B25FF19560A6; Wed, 20 May 2026 16:57:09 +0000 (UTC) Received: from [10.22.64.248] (unknown [10.22.64.248]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 67B7F1800352; Wed, 20 May 2026 16:57:08 +0000 (UTC) Message-ID: <3fc2e03f-d34f-4b87-8421-e28e94247757@redhat.com> Date: Wed, 20 May 2026 12:57:07 -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] debugobjects: Don't call fill_pool() in early boot non-task context of RT kernel To: Thomas Gleixner , Andrew Morton , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev References: <20260520164349.921226-1-longman@redhat.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20260520164349.921226-1-longman@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 5/20/26 12:43 PM, Waiman Long wrote: > When booting a debug PREEMPT_RT kernel on an arm64 system with grace > processor, the following lockdep splat 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 > {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+0x34/0xb0 > 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. > > It shouldn't really be a problem as fill_poll() will not called from > non-preemptible context after early boot, but the lockdep warning can > still cause confusion and anxiety. Fix that by further restricting the > call to only in_task() context during early boot. Sorry, the above paragraph isn't right. Will send out a v2. Cheers, Longman > 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) > > /* > * 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 < SYSTEM_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