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From: Peter Zijlstra <peterz@infradead.org>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Ingo Molnar <mingo@redhat.com>,
	Joel Fernandes <joel@joelfernandes.org>,
	John Ogness <john.ogness@linutronix.de>,
	Josh Triplett <josh@joshtriplett.org>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Neeraj Upadhyay <quic_neeraju@quicinc.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Waiman Long <longman@redhat.com>, Will Deacon <will@kernel.org>,
	Zqiang <qiang.zhang1211@gmail.com>
Subject: Re: [RFC PATCH] srcu: Use try-lock lockdep annotation for NMI-safe access.
Date: Thu, 28 Sep 2023 10:05:56 +0200	[thread overview]
Message-ID: <20230928080556.GE9829@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <ZRUX0YUrXfepRGKE@Boquns-Mac-mini.home>

On Wed, Sep 27, 2023 at 11:06:09PM -0700, Boqun Feng wrote:

> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index e85b5ad3e206..1af8d44e5eb4 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -5727,8 +5727,9 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
>                 return;
> 
>         if (unlikely(!lockdep_enabled())) {
> +               /* Only do NMI context checking if it's a check lock */
>                 /* XXX allow trylock from NMI ?!? */
> -               if (lockdep_nmi() && !trylock) {
> +               if (check && lockdep_nmi() && !trylock) {
>                         struct held_lock hlock;
> 
>                         hlock.acquire_ip = ip;
> 
> Peter, thoughts?
> 

I think I prefer the trylock one. Fundamentally trylock conveys the 'we
wont block' thing. Making 'lock' sometimes work for NMI is just
confusing.

  parent reply	other threads:[~2023-09-28  8:07 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-27 16:02 [RFC PATCH] srcu: Use try-lock lockdep annotation for NMI-safe access Sebastian Andrzej Siewior
2023-09-28  6:06 ` Boqun Feng
2023-09-28  6:33   ` Sebastian Andrzej Siewior
2023-09-28  8:05   ` Peter Zijlstra [this message]
2023-09-28  8:09   ` Peter Zijlstra
2023-09-28 14:54     ` Boqun Feng
2023-09-28 15:29       ` Peter Zijlstra
2023-09-28 17:09         ` Boqun Feng

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