From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Boqun Feng <boqun.feng@gmail.com>, Qian Cai <cai@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@kernel.org>, x86 <x86@kernel.org>,
linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org,
Linux Next Mailing List <linux-next@vger.kernel.org>,
Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [tip: locking/core] lockdep: Fix lockdep recursion
Date: Tue, 13 Oct 2020 12:34:06 +0200 [thread overview]
Message-ID: <20201013103406.GY2628@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201012212812.GH3249@paulmck-ThinkPad-P72>
On Mon, Oct 12, 2020 at 02:28:12PM -0700, Paul E. McKenney wrote:
> It is certainly an accident waiting to happen. Would something like
> the following make sense?
Sadly no.
> ------------------------------------------------------------------------
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index bfd38f2..52a63bc 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -4067,6 +4067,7 @@ void rcu_cpu_starting(unsigned int cpu)
>
> rnp = rdp->mynode;
> mask = rdp->grpmask;
> + lockdep_off();
> raw_spin_lock_irqsave_rcu_node(rnp, flags);
> WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
> newcpu = !(rnp->expmaskinitnext & mask);
> @@ -4086,6 +4087,7 @@ void rcu_cpu_starting(unsigned int cpu)
> } else {
> raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> }
> + lockdep_on();
> smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
> }
This will just shut it up, but will not fix the actual problem of that
spin-lock ending up in trace_lock_acquire() which relies on RCU which
isn't looking.
What we need here is to supress tracing not lockdep. Let me consider.
next prev parent reply other threads:[~2020-10-13 10:34 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <160223032121.7002.1269740091547117869.tip-bot2@tip-bot2>
2020-10-09 13:41 ` [tip: locking/core] lockdep: Fix lockdep recursion Qian Cai
2020-10-09 13:58 ` Paul E. McKenney
2020-10-09 15:30 ` Qian Cai
2020-10-09 16:11 ` Paul E. McKenney
2020-10-09 16:23 ` Peter Zijlstra
2020-10-09 16:37 ` Paul E. McKenney
2020-10-09 17:36 ` Qian Cai
2020-10-09 17:50 ` Paul E. McKenney
2020-10-09 17:54 ` Qian Cai
2020-10-09 18:21 ` Paul E. McKenney
2020-10-12 3:11 ` Boqun Feng
2020-10-12 14:14 ` Qian Cai
2020-10-12 21:28 ` Paul E. McKenney
2020-10-13 10:34 ` Peter Zijlstra [this message]
2020-10-13 10:44 ` Peter Zijlstra
2020-10-13 11:25 ` Peter Zijlstra
2020-10-13 16:26 ` Paul E. McKenney
2020-10-13 19:30 ` Paul E. McKenney
2020-10-14 18:34 ` Paul E. McKenney
2020-10-14 21:53 ` Peter Zijlstra
2020-10-14 22:11 ` Paul E. McKenney
2020-10-14 22:39 ` Peter Zijlstra
2020-10-14 23:55 ` Paul E. McKenney
2020-10-15 3:41 ` Paul E. McKenney
2020-10-15 9:49 ` Peter Zijlstra
2020-10-15 9:50 ` Peter Zijlstra
2020-10-15 16:15 ` Paul E. McKenney
2020-10-15 9:52 ` Peter Zijlstra
2020-10-15 16:20 ` Paul E. McKenney
2020-10-15 16:15 ` Paul E. McKenney
2020-10-15 17:23 ` Paul E. McKenney
2020-10-13 16:15 ` Paul E. McKenney
2020-10-13 10:27 ` Peter Zijlstra
2020-10-13 16:24 ` Boqun Feng
2020-10-27 19:31 ` Qian Cai
2020-10-28 3:01 ` Paul E. McKenney
2020-10-28 14:39 ` Qian Cai
2020-10-28 15:53 ` Paul E. McKenney
2020-10-28 20:08 ` Qian Cai
2020-10-28 21:02 ` Paul E. McKenney
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