From: "Paul E. McKenney" <paulmck@kernel.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: Zqiang <qiang.zhang1211@gmail.com>,
quic_neeraju@quicinc.com, joel@joelfernandes.org,
rcu@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock()
Date: Tue, 16 Jan 2024 08:59:17 -0800 [thread overview]
Message-ID: <7167b868-4160-47f0-8dd6-68c2af71e591@paulmck-laptop> (raw)
In-Reply-To: <ZaFkKPDTpCTXdyvT@lothringen>
On Fri, Jan 12, 2024 at 05:09:12PM +0100, Frederic Weisbecker wrote:
> On Wed, Jan 10, 2024 at 04:11:28PM +0800, Zqiang wrote:
> > For the kernels built with CONFIG_RCU_NOCB_CPU_DEFAULT_ALL=y and
> > CONFIG_RCU_LAZY=y, here are the following scenarios that will trigger
> > WARN_ON_ONCE() in the rcu_nocb_bypass_lock() and rcu_nocb_wait_contended().
> >
> > CPU2 CPU11
> > kthread
> > rcu_nocb_cb_kthread ksys_write
> > rcu_do_batch vfs_write
> > rcu_torture_timer_cb proc_sys_write
> > __kmem_cache_free proc_sys_call_handler
> > kmemleak_free drop_caches_sysctl_handler
> > delete_object_full drop_slab
> > __delete_object shrink_slab
> > put_object lazy_rcu_shrink_scan
> > call_rcu rcu_nocb_flush_bypass
> > __call_rcu_commn rcu_nocb_bypass_lock
> > raw_spin_trylock(&rdp->nocb_bypass_lock) fail
> > atomic_inc(&rdp->nocb_lock_contended);
> > rcu_nocb_wait_contended WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
> > WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)) |
> > |_ _ _ _ _ _ _ _ _ _same rdp and rdp->cpu != 11_ _ _ _ _ _ _ _ _ __|
> >
> > This commit therefore use the rcu_nocb_try_flush_bypass() instead of
> > rcu_nocb_flush_bypass() in lazy_rcu_shrink_scan(), if the nocb_bypass
> > queue is being flushed, the rcu_nocb_try_flush_bypass will return directly.
> >
> > Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
>
> Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Queued with Joel's and Frederic's Reviewed-by, thank you all!
Thanx, Paul
prev parent reply other threads:[~2024-01-16 16:59 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-10 8:11 [PATCH] rcu/nocb: Fix WARN_ON_ONCE() in the rcu_nocb_bypass_lock() Zqiang
2024-01-10 8:36 ` Z qiang
2024-01-11 11:54 ` Paul E. McKenney
2024-01-12 1:51 ` Joel Fernandes
2024-01-12 7:24 ` Z qiang
2024-01-12 13:50 ` Joel Fernandes
2024-01-12 7:23 ` Z qiang
2024-01-12 16:09 ` Frederic Weisbecker
2024-01-16 16:59 ` Paul E. McKenney [this message]
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