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Tue, 02 Jun 2026 22:26:46 -0400 X-MC-Unique: zKNFk-BkNSqRQDG8FyhqDA-1 X-Mimecast-MFC-AGG-ID: zKNFk-BkNSqRQDG8FyhqDA_1780453605 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 83B13195608B; Wed, 3 Jun 2026 02:26:44 +0000 (UTC) Received: from [10.22.80.32] (unknown [10.22.80.32]) by mx-prod-int-10.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2EB321681; Wed, 3 Jun 2026 02:26:42 +0000 (UTC) Message-ID: <19e9e41f-8590-427e-94ee-50911ccdc962@redhat.com> Date: Tue, 2 Jun 2026 22:26:42 -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-tip v3] debugobjects: Don't call fill_pool() in early boot non-task context 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: <20260520201509.931905-1-longman@redhat.com> Content-Language: en-US From: Waiman Long In-Reply-To: <20260520201509.931905-1-longman@redhat.com> 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 5/20/26 4:15 PM, 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 > : > > 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) > > /* > * 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 Ping. Any comment on this patch? Cheers, Longman