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 17:29:42 +0200 [thread overview]
Message-ID: <20230928152942.GE27245@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <ZRWTktRdej5OW53q@Boquns-Mac-mini.home>
On Thu, Sep 28, 2023 at 07:54:10AM -0700, Boqun Feng wrote:
> On Thu, Sep 28, 2023 at 10:09:00AM +0200, Peter Zijlstra wrote:
> > On Wed, Sep 27, 2023 at 11:06:09PM -0700, Boqun Feng wrote:
> >
> > > I think this is a "side-effect" of commit f0f44752f5f6 ("rcu: Annotate
> > > SRCU's update-side lockdep dependencies"). In verify_lock_unused(), i.e.
> > > the checking for NMI lock usages, the logic is that
> >
> > I think I'm having a problem with this commit -- that is, by adding
> > lockdep you're adding tracepoint, which rely on RCU being active.
> >
> > The result is that SRCU is now no longer usable from !RCU regions.
> >
>
> Interesting
>
> > Was this considered and intended?
> >
>
> No, I don't think I have considered this before, I think I may still
> miss something here, maybe you or Paul can provide an example for such
> a case?
The whole trace_.*_rcuidle() machinery. Which I thought I had fully
eradicated, but apparently still exists (with *one* user) :-/
Search for rcuidle in include/linux/tracepoint.h
Also, git grep trace_.*_rcuidle
next prev parent reply other threads:[~2023-09-28 15:30 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
2023-09-28 8:09 ` Peter Zijlstra
2023-09-28 14:54 ` Boqun Feng
2023-09-28 15:29 ` Peter Zijlstra [this message]
2023-09-28 17:09 ` Boqun Feng
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