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From: Valentin Schneider <vschneid@redhat.com>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E. McKenney"
 <paulmck@kernel.org>, Peter Zijlstra <peterz@infradead.org>, Neeraj
 Upadhyay <quic_neeraju@quicinc.com>, Joel Fernandes
 <joel@joelfernandes.org>, Josh Triplett <josh@joshtriplett.org>, Boqun
 Feng <boqun.feng@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, Mathieu
 Desnoyers <mathieu.desnoyers@efficios.com>, Lai Jiangshan
 <jiangshanlai@gmail.com>, Zqiang <qiang.zhang1211@gmail.com>
Subject: Re: [PATCH v2 27/27] context_tracking, rcu: Rename rcu_dyntick
 trace event into rcu_watching
In-Reply-To: <ZjuFUZXk4rYO4L2v@localhost.localdomain>
References: <20240430091740.1826862-1-vschneid@redhat.com>
 <20240430091740.1826862-28-vschneid@redhat.com>
 <ZjuFUZXk4rYO4L2v@localhost.localdomain>
Date: Mon, 13 May 2024 20:40:42 +0200
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On 08/05/24 15:59, Frederic Weisbecker wrote:
> Le Tue, Apr 30, 2024 at 11:17:31AM +0200, Valentin Schneider a =C3=A9crit=
 :
>> @@ -228,7 +228,7 @@ void noinstr ct_nmi_exit(void)
>>      }
>>
>>      /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
>> -	trace_rcu_dyntick(TPS("Startirq"), ct_nmi_nesting(), 0, ct_rcu_watchin=
g());
>> +	trace_rcu_watching(TPS("Endirq"), ct_nmi_nesting(), 0, ct_rcu_watching=
());
>
> Ah the initial string was wrong and you're fixing it, right?
>
> Should be a seperate patch?
>

No, I'm just creating confusion for everyone involved (including myself) :(
Dynticks start when RCU stops watching, so the naming logic gets flipped on
its head.

If I take the original comment from
bd2b879a1ca5 ("rcu: Add tracing to irq/NMI dyntick-idle transitions")
"""
as argument: "Start" for entering dyntick-idle mode, "Startirq" for
entering it from irq/NMI
"""

So here "Startirq" means "start dyntick mode from IRQ". With the name
change, it should be "Endirq", since RCU stops watching, from IRQ...

I know, a lot of confusion for 0 functional change :(