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From: Zhiguo Niu <niuzhiguo84@gmail.com>
Date: Wed, 3 Apr 2024 14:00:22 +0800
Message-ID: <CAHJ8P3L4oH25YMBkzpoZ0n2HwFBbFzt+seoZJkcy4_ZL5Ki5Xw@mail.gmail.com>
Subject: Re: [PATCH V4] lockdep: fix deadlock issue between lockdep and rcu
To: Carlos Llamas <cmllamas@google.com>
Cc: Zhiguo Niu <zhiguo.niu@unisoc.com>, peterz@infradead.org, mingo@redhat.com, 
	will@kernel.org, longman@redhat.com, boqun.feng@gmail.com, bvanassche@acm.org, 
	linux-kernel@vger.kernel.org, ke.wang@unisoc.com, xuewen.yan@unisoc.com, 
	hongyu.jin@unisoc.com
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On Tue, Apr 2, 2024 at 11:41=E2=80=AFPM Carlos Llamas <cmllamas@google.com>=
 wrote:
>
> On Tue, Feb 06, 2024 at 07:44:55PM +0800, Zhiguo Niu wrote:
> > There is a deadlock scenario between lockdep and rcu when
> > rcu nocb feature is enabled, just as following call stack:
> >
> >      rcuop/x
> > -000|queued_spin_lock_slowpath(lock =3D 0xFFFFFF817F2A8A80, val =3D ?)
> > -001|queued_spin_lock(inline) // try to hold nocb_gp_lock
> > -001|do_raw_spin_lock(lock =3D 0xFFFFFF817F2A8A80)
> > -002|__raw_spin_lock_irqsave(inline)
> > -002|_raw_spin_lock_irqsave(lock =3D 0xFFFFFF817F2A8A80)
> > -003|wake_nocb_gp_defer(inline)
> > -003|__call_rcu_nocb_wake(rdp =3D 0xFFFFFF817F30B680)
> > -004|__call_rcu_common(inline)
> > -004|call_rcu(head =3D 0xFFFFFFC082EECC28, func =3D ?)
> > -005|call_rcu_zapped(inline)
> > -005|free_zapped_rcu(ch =3D ?)// hold graph lock
> > -006|rcu_do_batch(rdp =3D 0xFFFFFF817F245680)
> > -007|nocb_cb_wait(inline)
> > -007|rcu_nocb_cb_kthread(arg =3D 0xFFFFFF817F245680)
> > -008|kthread(_create =3D 0xFFFFFF80803122C0)
> > -009|ret_from_fork(asm)
> >
> >      rcuop/y
> > -000|queued_spin_lock_slowpath(lock =3D 0xFFFFFFC08291BBC8, val =3D 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 =3D 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 =3D 0xFFFFFF817F2A8680)
> > -007|__call_rcu_common(inline)
> > -007|call_rcu(head =3D 0xFFFFFFC0822E0B58, func =3D ?)
> > -008|call_rcu_hurry(inline)
> > -008|rcu_sync_call(inline)
> > -008|rcu_sync_func(rhp =3D 0xFFFFFFC0822E0B58)
> > -009|rcu_do_batch(rdp =3D 0xFFFFFF817F266680)
> > -010|nocb_cb_wait(inline)
> > -010|rcu_nocb_cb_kthread(arg =3D 0xFFFFFF817F266680)
> > -011|kthread(_create =3D 0xFFFFFF8080363740)
> > -012|ret_from_fork(asm)
> >
> > rcuop/x and rcuop/y are rcu nocb threads with the same nocb gp thread.
> > This patch release the graph lock before lockdep call_rcu.
> >
> > Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no lo=
nger in use")
> > Cc: <stable@vger.kernel.org>
> > Cc: Boqun Feng <boqun.feng@gmail.com>
> > Cc: Waiman Long <longman@redhat.com>
> > Cc: Carlos Llamas <cmllamas@google.com>
> > Cc: Bart Van Assche <bvanassche@acm.org>
> > Signed-off-by: Zhiguo Niu <zhiguo.niu@unisoc.com>
> > Signed-off-by: Xuewen Yan <xuewen.yan@unisoc.com>
> > Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
> > Reviewed-by: Waiman Long <longman@redhat.com>
> > Reviewed-by: Carlos Llamas <cmllamas@google.com>
> > Reviewed-by: Bart Van Assche <bvanassche@acm.org>
> > ---
>
> This patch should be good to go. Maybe it just slipped through the
> cracks. Ingo, will you be taking this?

Hi Carlos,
Thanks for restoring this mail and now this patch can only be
temporarily included in my code locally when I do related jobs.
and hope someone can help merge it if there are no review suggestions.
>
> --
> Carlos Llamas