linux-kernel - Re: [PATCH V2] lockdep: fix deadlock issue between lockdep and rcu

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Date: Thu, 1 Feb 2024 11:28:08 -0800
From: Bart Van Assche <bvanassche@....org>
To: Zhiguo Niu <zhiguo.niu@...soc.com>, peterz@...radead.org,
 mingo@...hat.com, will@...nel.org, longman@...hat.com, boqun.feng@...il.com
Cc: linux-kernel@...r.kernel.org, niuzhiguo84@...il.com, ke.wang@...soc.com,
 xuewen.yan@...soc.com, Carlos Llamas <cmllamas@...gle.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH V2] lockdep: fix deadlock issue between lockdep and rcu

On 1/16/24 23:48, Zhiguo Niu wrote:
> -000|queued_spin_lock_slowpath(lock = 0xFFFFFFC08291BBC8, val = 0)
> -001|queued_spin_lock()
> -001|lockdep_lock()
> -001|graph_lock() // try to hold graph lock
> -002|lookup_chain_cache_add()
> -002|validate_chain()
> -003|lock_acquire
> -004|_raw_spin_lock_irqsave(lock = 0xFFFFFF817F211D80)
> -005|lock_timer_base(inline)
> -006|mod_timer(inline)
> -006|wake_nocb_gp_defer(inline)// hold nocb_gp_lock
> -006|__call_rcu_nocb_wake(rdp = 0xFFFFFF817F2A8680)
> -007|__call_rcu_common(inline)
> -007|call_rcu(head = 0xFFFFFFC0822E0B58, func = ?)
> -008|call_rcu_hurry(inline)
> -008|rcu_sync_call(inline)
> -008|rcu_sync_func(rhp = 0xFFFFFFC0822E0B58)
> -009|rcu_do_batch(rdp = 0xFFFFFF817F266680)
> -010|nocb_cb_wait(inline)
> -010|rcu_nocb_cb_kthread(arg = 0xFFFFFF817F266680)
> -011|kthread(_create = 0xFFFFFF8080363740)
> -012|ret_from_fork(asm)

The above call trace shows a graph_lock() call from inside lock_timer_base().
How can that happen? In lock_timer_base() I see a raw_spin_lock_irqsave() call.
Did I perhaps overlook something?

Thanks,

Bart.